Improve empty pipelines (#7383)

# Description

This fix changes pipelines to allow them to actually be empty. Mapping
over empty pipelines gives empty pipelines. Empty pipelines immediately
return `None` when iterated.

This removes a some of where `Span::new(0, 0)` was coming from, though
there are other cases where we still use it.

# User-Facing Changes

None

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-cli/src/completions/completer.rs

@@ -92,7 +92,7 @@ impl NuCompleter {
             &self.engine_state,
             &mut callee_stack,
             block,
-            PipelineData::new(span),
+            PipelineData::empty(),
             true,
             true,
         );

crates/nu-cli/src/completions/custom_completions.rs

@@ -67,7 +67,7 @@ impl Completer for CustomCompletion {
                 redirect_stdout: true,
                 redirect_stderr: true,
             },
-            PipelineData::new(span),
+            PipelineData::empty(),
         );
 
         let mut custom_completion_options = None;

crates/nu-cli/src/config_files.rs

@@ -8,7 +8,7 @@ use nu_path::canonicalize_with;
 use nu_protocol::engine::{EngineState, Stack, StateWorkingSet};
 #[cfg(feature = "plugin")]
 use nu_protocol::Spanned;
-use nu_protocol::{HistoryFileFormat, PipelineData, Span};
+use nu_protocol::{HistoryFileFormat, PipelineData};
 use std::path::PathBuf;
 
 #[cfg(feature = "plugin")]
@@ -38,7 +38,7 @@ pub fn read_plugin_file(
                 stack,
                 &contents,
                 &plugin_filename,
-                PipelineData::new(Span::new(0, 0)),
+                PipelineData::empty(),
             );
         }
     }
@@ -85,7 +85,7 @@ pub fn eval_config_contents(
                 stack,
                 &contents,
                 &config_filename,
-                PipelineData::new(Span::new(0, 0)),
+                PipelineData::empty(),
             );
 
             // Merge the environment in case env vars changed in the config

crates/nu-cli/src/eval_file.rs

@@ -39,13 +39,7 @@ pub fn evaluate_file(
     if working_set.find_decl(b"main", &Type::Any).is_some() {
         let args = format!("main {}", args.join(" "));
 
-        if !eval_source(
-            engine_state,
-            stack,
-            &file,
-            &path,
-            PipelineData::new(Span::new(0, 0)),
-        ) {
+        if !eval_source(engine_state, stack, &file, &path, PipelineData::empty()) {
             std::process::exit(1);
         }
         if !eval_source(engine_state, stack, args.as_bytes(), "<commandline>", input) {

crates/nu-cli/src/print.rs

@@ -50,14 +50,13 @@ Since this command has no output, there is no point in piping it with other comm
         let args: Vec<Value> = call.rest(engine_state, stack, 0)?;
         let no_newline = call.has_flag("no-newline");
         let to_stderr = call.has_flag("stderr");
-        let head = call.head;
 
         for arg in args {
             arg.into_pipeline_data()
                 .print(engine_state, stack, no_newline, to_stderr)?;
         }
 
-        Ok(PipelineData::new(head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-cli/src/prompt_update.rs

@@ -4,7 +4,7 @@ use log::info;
 use nu_engine::eval_subexpression;
 use nu_protocol::{
     engine::{EngineState, Stack, StateWorkingSet},
-    Config, PipelineData, Span, Value,
+    Config, PipelineData, Value,
 };
 use reedline::Prompt;
 
@@ -37,12 +37,8 @@ fn get_prompt_string(
                 let block = engine_state.get_block(block_id);
                 let mut stack = stack.captures_to_stack(&captures);
                 // Use eval_subexpression to force a redirection of output, so we can use everything in prompt
-                let ret_val = eval_subexpression(
-                    engine_state,
-                    &mut stack,
-                    block,
-                    PipelineData::new(Span::new(0, 0)), // Don't try this at home, 0 span is ignored
-                );
+                let ret_val =
+                    eval_subexpression(engine_state, &mut stack, block, PipelineData::empty());
                 info!(
                     "get_prompt_string (block) {}:{}:{}",
                     file!(),
@@ -62,12 +58,7 @@ fn get_prompt_string(
             Value::Block { val: block_id, .. } => {
                 let block = engine_state.get_block(block_id);
                 // Use eval_subexpression to force a redirection of output, so we can use everything in prompt
-                let ret_val = eval_subexpression(
-                    engine_state,
-                    stack,
-                    block,
-                    PipelineData::new(Span::new(0, 0)), // Don't try this at home, 0 span is ignored
-                );
+                let ret_val = eval_subexpression(engine_state, stack, block, PipelineData::empty());
                 info!(
                     "get_prompt_string (block) {}:{}:{}",
                     file!(),

crates/nu-cli/src/repl.rs

@@ -149,7 +149,7 @@ pub fn evaluate_repl(
             stack,
             s.item.as_bytes(),
             &format!("entry #{}", entry_num),
-            PipelineData::new(Span::new(0, 0)),
+            PipelineData::empty(),
         );
         engine_state.merge_env(stack, get_guaranteed_cwd(engine_state, stack))?;
     }
@@ -431,7 +431,7 @@ pub fn evaluate_repl(
                         stack,
                         s.as_bytes(),
                         &format!("entry #{}", entry_num),
-                        PipelineData::new(Span::new(0, 0)),
+                        PipelineData::empty(),
                     );
                 }
                 let cmd_duration = start_time.elapsed();
@@ -637,7 +637,7 @@ pub fn eval_string_with_input(
 
     let input_as_pipeline_data = match input {
         Some(input) => PipelineData::Value(input, None),
-        None => PipelineData::new(Span::test_data()),
+        None => PipelineData::empty(),
     };
 
     eval_block(
@@ -722,7 +722,7 @@ pub fn eval_hook(
         val: "condition".to_string(),
         span: value_span,
     };
-    let mut output = PipelineData::new(Span::new(0, 0));
+    let mut output = PipelineData::empty();
 
     let code_path = PathMember::String {
         val: "code".to_string(),
@@ -823,7 +823,7 @@ pub fn eval_hook(
                         };
 
                         engine_state.merge_delta(delta)?;
-                        let input = PipelineData::new(value_span);
+                        let input = PipelineData::empty();
 
                         let var_ids: Vec<VarId> = vars
                             .into_iter()
@@ -943,7 +943,7 @@ pub fn run_hook_block(
 ) -> Result<Value, ShellError> {
     let block = engine_state.get_block(block_id);
 
-    let input = optional_input.unwrap_or_else(|| PipelineData::new(span));
+    let input = optional_input.unwrap_or_else(PipelineData::empty);
 
     let mut callee_stack = stack.gather_captures(&block.captures);
 

crates/nu-command/src/core_commands/alias.rs

@@ -43,10 +43,10 @@ impl Command for Alias {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/ast.rs

@@ -37,14 +37,13 @@ impl Command for Ast {
         call: &Call,
         _input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        let head = call.head;
         let pipeline: Spanned<String> = call.req(engine_state, stack, 0)?;
         let mut working_set = StateWorkingSet::new(engine_state);
 
         let (output, err) = parse(&mut working_set, None, pipeline.item.as_bytes(), false, &[]);
         eprintln!("output: {:#?}\nerror: {:#?}", output, err);
 
-        Ok(PipelineData::new(head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/def.rs

@@ -36,10 +36,10 @@ impl Command for Def {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/def_env.rs

@@ -62,10 +62,10 @@ def-env cd_with_fallback [arg = ""] {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/do_.rs

@@ -169,9 +169,9 @@ impl Command for Do {
                 trim_end_newline,
             }),
             Ok(PipelineData::Value(Value::Error { .. }, ..)) if ignore_shell_errors => {
-                Ok(PipelineData::new(call.head))
+                Ok(PipelineData::empty())
             }
-            Err(_) if ignore_shell_errors => Ok(PipelineData::new(call.head)),
+            Err(_) if ignore_shell_errors => Ok(PipelineData::empty()),
             r => r,
         }
     }

crates/nu-command/src/core_commands/export_alias.rs

@@ -39,10 +39,10 @@ impl Command for ExportAlias {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/export_def.rs

@@ -36,10 +36,10 @@ impl Command for ExportDef {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/export_def_env.rs

@@ -62,10 +62,10 @@ export def-env cd_with_fallback [arg = ""] {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/export_extern.rs

@@ -35,10 +35,10 @@ impl Command for ExportExtern {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/export_use.rs

@@ -34,10 +34,10 @@ impl Command for ExportUse {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/extern_.rs

@@ -35,10 +35,10 @@ impl Command for Extern {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/for_.rs

@@ -110,7 +110,7 @@ impl Command for For {
                         &engine_state,
                         stack,
                         &block,
-                        PipelineData::new(head),
+                        PipelineData::empty(),
                         redirect_stdout,
                         redirect_stderr,
                     ) {
@@ -155,7 +155,7 @@ impl Command for For {
                         &engine_state,
                         stack,
                         &block,
-                        PipelineData::new(head),
+                        PipelineData::empty(),
                         redirect_stdout,
                         redirect_stderr,
                     ) {
@@ -181,14 +181,14 @@ impl Command for For {
                     &engine_state,
                     stack,
                     &block,
-                    PipelineData::new(head),
+                    PipelineData::empty(),
                     redirect_stdout,
                     redirect_stderr,
                 )?
                 .into_value(head);
             }
         }
-        Ok(PipelineData::new(head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/hide.rs

@@ -62,7 +62,7 @@ This command is a parser keyword. For details, check:
 
         stack.remove_env_var(engine_state, &env_var_name.item);
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/hide_env.rs

@@ -63,7 +63,7 @@ impl Command for HideEnv {
             }
         }
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/if_.rs

@@ -102,7 +102,7 @@ impl Command for If {
                         .map(|res| res.0)
                     }
                 } else {
-                    Ok(PipelineData::new(call.head))
+                    Ok(PipelineData::empty())
                 }
             }
             x => Err(ShellError::CantConvert(

crates/nu-command/src/core_commands/ignore.rs

@@ -32,7 +32,7 @@ impl Command for Ignore {
         input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
         input.into_value(call.head);
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/let_.rs

@@ -73,7 +73,7 @@ impl Command for Let {
         //println!("Adding: {:?} to {}", rhs, var_id);
 
         stack.add_var(var_id, rhs.into_value(call.head));
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/loop_.rs

@@ -55,7 +55,7 @@ impl Command for Loop {
                 engine_state,
                 stack,
                 block,
-                PipelineData::new(call.head),
+                PipelineData::empty(),
                 call.redirect_stdout,
                 call.redirect_stderr,
             ) {
@@ -73,7 +73,7 @@ impl Command for Loop {
                 }
             }
         }
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/module.rs

@@ -35,10 +35,10 @@ impl Command for Module {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/mut_.rs

@@ -73,7 +73,7 @@ impl Command for Mut {
         //println!("Adding: {:?} to {}", rhs, var_id);
 
         stack.add_var(var_id, rhs.into_value(call.head));
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/overlay/hide.rs

@@ -88,7 +88,7 @@ impl Command for OverlayHide {
             stack.add_env_var(name, val);
         }
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/overlay/new.rs

@@ -49,7 +49,7 @@ This command is a parser keyword. For details, check:
 
         stack.add_overlay(name_arg.item);
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/overlay/use_.rs

@@ -172,7 +172,7 @@ impl Command for OverlayUse {
             caller_stack.add_overlay(overlay_name);
         }
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/register.rs

@@ -49,10 +49,10 @@ impl Command for Register {
         &self,
         _engine_state: &EngineState,
         _stack: &mut Stack,
-        call: &Call,
+        _call: &Call,
         _input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/try_.rs

@@ -71,12 +71,12 @@ impl Command for Try {
                         engine_state,
                         stack,
                         catch_block,
-                        PipelineData::new(call.head),
+                        PipelineData::empty(),
                         false,
                         false,
                     )
                 } else {
-                    Ok(PipelineData::new(call.head))
+                    Ok(PipelineData::empty())
                 }
             }
             // external command may fail to run
@@ -118,12 +118,12 @@ impl Command for Try {
                             engine_state,
                             stack,
                             catch_block,
-                            PipelineData::new(call.head),
+                            PipelineData::empty(),
                             false,
                             false,
                         )
                     } else {
-                        Ok(PipelineData::new(call.head))
+                        Ok(PipelineData::empty())
                     }
                 } else {
                     Ok(PipelineData::ExternalStream {

crates/nu-command/src/core_commands/use_.rs

@@ -112,7 +112,7 @@ impl Command for Use {
             ));
         }
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/core_commands/while_.rs

@@ -63,7 +63,7 @@ impl Command for While {
                             engine_state,
                             stack,
                             block,
-                            PipelineData::new(call.head),
+                            PipelineData::empty(),
                             call.redirect_stdout,
                             call.redirect_stderr,
                         ) {
@@ -94,7 +94,7 @@ impl Command for While {
                 }
             }
         }
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/dataframe/test_dataframe.rs

@@ -22,7 +22,7 @@ pub fn test_dataframe(cmds: Vec<Box<dyn Command + 'static>>) {
     let delta = {
         // Base functions that are needed for testing
         // Try to keep this working set small to keep tests running as fast as possible
-        let mut working_set = StateWorkingSet::new(&*engine_state);
+        let mut working_set = StateWorkingSet::new(&engine_state);
         working_set.add_decl(Box::new(Let));
         working_set.add_decl(Box::new(ToDataFrame));
         working_set.add_decl(Box::new(ToLazyFrame));
@@ -49,7 +49,7 @@ pub fn test_dataframe(cmds: Vec<Box<dyn Command + 'static>>) {
         let start = std::time::Instant::now();
 
         let (block, delta) = {
-            let mut working_set = StateWorkingSet::new(&*engine_state);
+            let mut working_set = StateWorkingSet::new(&engine_state);
             let (output, err) = parse(
                 &mut working_set,
                 None,
@@ -75,7 +75,7 @@ pub fn test_dataframe(cmds: Vec<Box<dyn Command + 'static>>) {
             &engine_state,
             &mut stack,
             &block,
-            PipelineData::new(Span::test_data()),
+            PipelineData::empty(),
             true,
             true,
         ) {

crates/nu-command/src/env/config/config_reset.rs

@@ -108,6 +108,6 @@ impl Command for ConfigReset {
                 }
             }
         }
-        Ok(PipelineData::new(span))
+        Ok(PipelineData::empty())
     }
 }

crates/nu-command/src/env/export_env.rs

@@ -50,7 +50,7 @@ impl Command for ExportEnv {
 
         redirect_env(engine_state, caller_stack, &callee_stack);
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/env/let_env.rs

@@ -57,7 +57,7 @@ impl Command for LetEnv {
         } else {
             stack.add_env_var(env_var.item, rhs);
         }
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/env/load_env.rs

@@ -57,7 +57,7 @@ impl Command for LoadEnv {
                         stack.add_env_var(env_var, rhs);
                     }
                 }
-                Ok(PipelineData::new(call.head))
+                Ok(PipelineData::empty())
             }
             None => match input {
                 PipelineData::Value(Value::Record { cols, vals, .. }, ..) => {
@@ -81,7 +81,7 @@ impl Command for LoadEnv {
                             stack.add_env_var(env_var, rhs);
                         }
                     }
-                    Ok(PipelineData::new(call.head))
+                    Ok(PipelineData::empty())
                 }
                 _ => Err(ShellError::UnsupportedInput(
                     "'load-env' expects a single record".into(),

crates/nu-command/src/example_test.rs

@@ -59,7 +59,7 @@ mod test_examples {
         let delta = {
             // Base functions that are needed for testing
             // Try to keep this working set small to keep tests running as fast as possible
-            let mut working_set = StateWorkingSet::new(&*engine_state);
+            let mut working_set = StateWorkingSet::new(&engine_state);
             working_set.add_decl(Box::new(Let));
             working_set.add_decl(Box::new(Str));
             working_set.add_decl(Box::new(StrJoin));
@@ -215,10 +215,10 @@ mod test_examples {
         );
 
         engine_state
-            .merge_env(&mut stack, &cwd)
+            .merge_env(&mut stack, cwd)
             .expect("Error merging environment");
 
-        let empty_input = PipelineData::new(Span::test_data());
+        let empty_input = PipelineData::empty();
         let result = eval(example.example, empty_input, cwd, engine_state);
 
         // Note. Value implements PartialEq for Bool, Int, Float, String and Block
@@ -320,7 +320,7 @@ mod test_examples {
                 block.pipelines[0].elements.truncate(&n_expressions - 1);
 
                 if !block.pipelines[0].elements.is_empty() {
-                    let empty_input = PipelineData::new(Span::test_data());
+                    let empty_input = PipelineData::empty();
                     Some(eval_block(block, empty_input, cwd, engine_state, delta))
                 } else {
                     Some(Value::nothing(Span::test_data()))

crates/nu-command/src/filesystem/cd.rs

@@ -196,7 +196,7 @@ impl Command for Cd {
         match have_permission(&path_tointo) {
             PermissionResult::PermissionOk => {
                 stack.add_env_var("PWD".into(), path_value);
-                Ok(PipelineData::new(call.head))
+                Ok(PipelineData::empty())
             }
             PermissionResult::PermissionDenied(reason) => Err(ShellError::IOError(format!(
                 "Cannot change directory to {}: {}",

crates/nu-command/src/filesystem/save.rs

@@ -2,8 +2,7 @@ use nu_engine::CallExt;
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{
-    Category, Example, PipelineData, RawStream, ShellError, Signature, Span, Spanned, SyntaxShape,
-    Value,
+    Category, Example, PipelineData, RawStream, ShellError, Signature, Spanned, SyntaxShape, Value,
 };
 use std::fs::File;
 use std::io::{BufWriter, Write};
@@ -160,7 +159,7 @@ impl Command for Save {
                         file.flush()?
                     }
 
-                    Ok(PipelineData::new(span))
+                    Ok(PipelineData::empty())
                 }
                 Value::Binary { val, .. } => {
                     if let Err(err) = file.write_all(&val) {
@@ -169,7 +168,7 @@ impl Command for Save {
                         file.flush()?
                     }
 
-                    Ok(PipelineData::new(span))
+                    Ok(PipelineData::empty())
                 }
                 Value::List { vals, .. } => {
                     let val = vals
@@ -185,7 +184,7 @@ impl Command for Save {
                         file.flush()?
                     }
 
-                    Ok(PipelineData::new(span))
+                    Ok(PipelineData::empty())
                 }
                 v => Err(ShellError::UnsupportedInput(
                     format!("{:?} not supported", v.get_type()),
@@ -194,7 +193,7 @@ impl Command for Save {
             }
         } else {
             match input {
-                PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(span)),
+                PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
                 PipelineData::ExternalStream {
                     stdout: Some(stream),
                     stderr,
@@ -202,16 +201,16 @@ impl Command for Save {
                 } => {
                     // delegate a thread to redirect stderr to result.
                     let handler = stderr.map(|stderr_stream| match stderr_file {
-                        Some(stderr_file) => std::thread::spawn(move || {
-                            stream_to_file(stderr_stream, stderr_file, span)
-                        }),
+                        Some(stderr_file) => {
+                            std::thread::spawn(move || stream_to_file(stderr_stream, stderr_file))
+                        }
                         None => std::thread::spawn(move || {
                             let _ = stderr_stream.into_bytes();
-                            Ok(PipelineData::new(span))
+                            Ok(PipelineData::empty())
                         }),
                     });
 
-                    let res = stream_to_file(stream, file, span);
+                    let res = stream_to_file(stream, file);
                     if let Some(h) = handler {
                         match h.join() {
                             Err(err) => {
@@ -236,7 +235,7 @@ impl Command for Save {
                             file.flush()?
                         }
 
-                        Ok(PipelineData::new(span))
+                        Ok(PipelineData::empty())
                     }
                     Value::Binary { val, .. } => {
                         if let Err(err) = file.write_all(&val) {
@@ -245,7 +244,7 @@ impl Command for Save {
                             file.flush()?
                         }
 
-                        Ok(PipelineData::new(span))
+                        Ok(PipelineData::empty())
                     }
                     Value::List { vals, .. } => {
                         let val = vals
@@ -261,7 +260,7 @@ impl Command for Save {
                             file.flush()?
                         }
 
-                        Ok(PipelineData::new(span))
+                        Ok(PipelineData::empty())
                     }
                     v => Err(ShellError::UnsupportedInput(
                         format!("{:?} not supported", v.get_type()),
@@ -303,11 +302,7 @@ impl Command for Save {
     }
 }
 
-fn stream_to_file(
-    mut stream: RawStream,
-    file: File,
-    span: Span,
-) -> Result<PipelineData, ShellError> {
+fn stream_to_file(mut stream: RawStream, file: File) -> Result<PipelineData, ShellError> {
     let mut writer = BufWriter::new(file);
 
     stream
@@ -331,5 +326,5 @@ fn stream_to_file(
             }
             Ok(())
         })
-        .map(|_| PipelineData::new(span))
+        .map(|_| PipelineData::empty())
 }

crates/nu-command/src/filesystem/touch.rs

@@ -190,7 +190,7 @@ impl Command for Touch {
             }
         }
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/filesystem/watch.rs

@@ -271,7 +271,7 @@ impl Command for Watch {
             }
         }
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/filters/columns.rs

@@ -72,6 +72,7 @@ fn getcol(
     input: PipelineData,
 ) -> Result<PipelineData, ShellError> {
     match input {
+        PipelineData::Empty => Ok(PipelineData::Empty),
         PipelineData::Value(
             Value::List {
                 vals: input_vals,

crates/nu-command/src/filters/each.rs

@@ -156,6 +156,7 @@ with 'transpose' first."#
         let redirect_stderr = call.redirect_stderr;
 
         match input {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::Value(Value::Range { .. }, ..)
             | PipelineData::Value(Value::List { .. }, ..)
             | PipelineData::ListStream { .. } => Ok(input
@@ -223,7 +224,7 @@ with 'transpose' first."#
                     }
                 })
                 .into_pipeline_data(ctrlc)),
-            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(call.head)),
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 ..

crates/nu-command/src/filters/each_while.rs

@@ -116,6 +116,7 @@ impl Command for EachWhile {
         let redirect_stderr = call.redirect_stderr;
 
         match input {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::Value(Value::Range { .. }, ..)
             | PipelineData::Value(Value::List { .. }, ..)
             | PipelineData::ListStream { .. } => Ok(input
@@ -186,7 +187,7 @@ impl Command for EachWhile {
                 })
                 .fuse()
                 .into_pipeline_data(ctrlc)),
-            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(call.head)),
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 ..

crates/nu-command/src/filters/empty.rs

@@ -103,6 +103,7 @@ fn empty(
         .into_pipeline_data())
     } else {
         match input {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::ExternalStream { stdout, .. } => match stdout {
                 Some(s) => {
                     let bytes = s.into_bytes();

crates/nu-command/src/filters/find.rs

@@ -321,6 +321,7 @@ fn find_with_rest_and_highlight(
     let ls_colors = get_ls_colors(ls_colors_env_str);
 
     match input {
+        PipelineData::Empty => Ok(PipelineData::Empty),
         PipelineData::Value(_, _) => input
             .map(
                 move |mut x| match &mut x {
@@ -446,7 +447,7 @@ fn find_with_rest_and_highlight(
         )
         .into_pipeline_data(ctrlc)
         .set_metadata(meta)),
-        PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(span)),
+        PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
         PipelineData::ExternalStream {
             stdout: Some(stream),
             ..

crates/nu-command/src/filters/last.rs

@@ -110,7 +110,7 @@ impl Command for Last {
             if let Some(last) = last {
                 Ok(last.into_pipeline_data().set_metadata(metadata))
             } else {
-                Ok(PipelineData::new(span).set_metadata(metadata))
+                Ok(PipelineData::empty().set_metadata(metadata))
             }
         }
     }

crates/nu-command/src/filters/length.rs

@@ -97,6 +97,7 @@ fn getcol(
     input: PipelineData,
 ) -> Result<PipelineData, ShellError> {
     match input {
+        PipelineData::Empty => Ok(PipelineData::Empty),
         PipelineData::Value(
             Value::List {
                 vals: input_vals,

crates/nu-command/src/filters/lines.rs

@@ -71,6 +71,7 @@ impl Command for Lines {
 
                 Ok(iter.into_pipeline_data(engine_state.ctrlc.clone()))
             }
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::ListStream(stream, ..) => {
                 let iter = stream
                     .into_iter()
@@ -112,7 +113,7 @@ impl Command for Lines {
                 format!("Not supported input: {}", val.as_string()?),
                 head,
             )),
-            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(head)),
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 ..

crates/nu-command/src/filters/par_each.rs

@@ -81,6 +81,7 @@ impl Command for ParEach {
         let redirect_stderr = call.redirect_stderr;
 
         match input {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::Value(Value::Range { val, .. }, ..) => Ok(val
                 .into_range_iter(ctrlc.clone())?
                 .enumerate()
@@ -272,7 +273,7 @@ impl Command for ParEach {
                 .into_iter()
                 .flatten()
                 .into_pipeline_data(ctrlc)),
-            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(call.head)),
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 ..

crates/nu-command/src/filters/reduce.rs

@@ -219,7 +219,7 @@ impl Command for Reduce {
                 engine_state,
                 &mut stack,
                 block,
-                PipelineData::new(span),
+                PipelineData::empty(),
                 // redirect stdout until its the last input value
                 redirect_stdout || input_iter.peek().is_some(),
                 redirect_stderr,

crates/nu-command/src/filters/select.rs

@@ -249,7 +249,7 @@ fn select(
                 Ok(v.into_pipeline_data().set_metadata(metadata))
             }
         }
-        _ => Ok(PipelineData::new(span)),
+        _ => Ok(PipelineData::empty()),
     }
 }
 

crates/nu-command/src/filters/skip/skip_until.rs

@@ -96,7 +96,7 @@ impl Command for SkipUntil {
                     &engine_state,
                     &mut stack,
                     &block,
-                    PipelineData::new(span),
+                    PipelineData::empty(),
                     redirect_stdout,
                     redirect_stderr,
                 )

crates/nu-command/src/filters/skip/skip_while.rs

@@ -97,7 +97,7 @@ impl Command for SkipWhile {
                     &engine_state,
                     &mut stack,
                     &block,
-                    PipelineData::new(span),
+                    PipelineData::empty(),
                     redirect_stdout,
                     redirect_stderr,
                 )

crates/nu-command/src/filters/take/take_until.rs

@@ -92,7 +92,7 @@ impl Command for TakeUntil {
                     &engine_state,
                     &mut stack,
                     &block,
-                    PipelineData::new(span),
+                    PipelineData::empty(),
                     redirect_stdout,
                     redirect_stderr,
                 )

crates/nu-command/src/filters/take/take_while.rs

@@ -92,7 +92,7 @@ impl Command for TakeWhile {
                     &engine_state,
                     &mut stack,
                     &block,
-                    PipelineData::new(span),
+                    PipelineData::empty(),
                     redirect_stdout,
                     redirect_stderr,
                 )

crates/nu-command/src/filters/where_.rs

@@ -62,6 +62,7 @@ impl Command for Where {
             let redirect_stderr = call.redirect_stderr;
 
             match input {
+                PipelineData::Empty => Ok(PipelineData::Empty),
                 PipelineData::Value(Value::Range { .. }, ..)
                 | PipelineData::Value(Value::List { .. }, ..)
                 | PipelineData::ListStream { .. } => Ok(input
@@ -115,9 +116,7 @@ impl Command for Where {
                         }
                     })
                     .into_pipeline_data(ctrlc)),
-                PipelineData::ExternalStream { stdout: None, .. } => {
-                    Ok(PipelineData::new(call.head))
-                }
+                PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
                 PipelineData::ExternalStream {
                     stdout: Some(stream),
                     ..

crates/nu-command/src/filters/wrap.rs

@@ -39,6 +39,7 @@ impl Command for Wrap {
         let name: String = call.req(engine_state, stack, 0)?;
 
         match input {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::Value(Value::Range { .. }, ..)
             | PipelineData::Value(Value::List { .. }, ..)
             | PipelineData::ListStream { .. } => Ok(input

crates/nu-command/src/misc/history.rs

@@ -54,7 +54,7 @@ impl Command for History {
             if clear {
                 let _ = std::fs::remove_file(history_path);
                 // TODO: FIXME also clear the auxiliary files when using sqlite
-                Ok(PipelineData::new(head))
+                Ok(PipelineData::empty())
             } else {
                 let history_reader: Option<Box<dyn ReedlineHistory>> =
                     match engine_state.config.history_file_format {

crates/nu-command/src/network/fetch.rs

@@ -176,7 +176,7 @@ impl Command for SubCommand {
                                     file.flush()?
                                 }
 
-                                Ok(PipelineData::new(span))
+                                Ok(PipelineData::empty())
                             }
                             Value::Binary { val, .. } => {
                                 if let Err(err) = file.write_all(&val) {
@@ -185,7 +185,7 @@ impl Command for SubCommand {
                                     file.flush()?
                                 }
 
-                                Ok(PipelineData::new(span))
+                                Ok(PipelineData::empty())
                             }
                             Value::List { vals, .. } => {
                                 let val = vals
@@ -201,7 +201,7 @@ impl Command for SubCommand {
                                     file.flush()?
                                 }
 
-                                Ok(PipelineData::new(span))
+                                Ok(PipelineData::empty())
                             }
                             v => Err(ShellError::UnsupportedInput(
                                 format!("{:?} not supported", v.get_type()),
@@ -211,7 +211,7 @@ impl Command for SubCommand {
                     } else {
                         match value {
                             PipelineData::ExternalStream { stdout: None, .. } => {
-                                Ok(PipelineData::new(span))
+                                Ok(PipelineData::empty())
                             }
                             PipelineData::ExternalStream {
                                 stdout: Some(mut stream),
@@ -240,7 +240,7 @@ impl Command for SubCommand {
                                         }
                                         Ok(())
                                     })
-                                    .map(|_| PipelineData::new(span))
+                                    .map(|_| PipelineData::empty())
                             }
                             value => match value.into_value(span) {
                                 Value::String { val, .. } => {
@@ -250,7 +250,7 @@ impl Command for SubCommand {
                                         file.flush()?
                                     }
 
-                                    Ok(PipelineData::new(span))
+                                    Ok(PipelineData::empty())
                                 }
                                 Value::Binary { val, .. } => {
                                     if let Err(err) = file.write_all(&val) {
@@ -259,7 +259,7 @@ impl Command for SubCommand {
                                         file.flush()?
                                     }
 
-                                    Ok(PipelineData::new(span))
+                                    Ok(PipelineData::empty())
                                 }
                                 Value::List { vals, .. } => {
                                     let val = vals
@@ -275,7 +275,7 @@ impl Command for SubCommand {
                                         file.flush()?
                                     }
 
-                                    Ok(PipelineData::new(span))
+                                    Ok(PipelineData::empty())
                                 }
                                 v => Err(ShellError::UnsupportedInput(
                                     format!("{:?} not supported", v.get_type()),

crates/nu-command/src/shells/enter.rs

@@ -99,7 +99,7 @@ impl Command for Enter {
 
         stack.add_env_var("PWD".into(), new_path);
 
-        Ok(PipelineData::new(call.head))
+        Ok(PipelineData::empty())
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-command/src/shells/exit.rs

@@ -101,7 +101,7 @@ impl Command for Exit {
 
             stack.add_env_var("PWD".into(), new_path);
 
-            Ok(PipelineData::new(call.head))
+            Ok(PipelineData::empty())
         }
     }
 

crates/nu-command/src/shells/mod.rs

@@ -121,7 +121,7 @@ fn switch_shell(
 
     stack.add_env_var("PWD".into(), new_path);
 
-    Ok(PipelineData::new(call.head))
+    Ok(PipelineData::empty())
 }
 
 fn list_shells(

crates/nu-command/src/strings/detect_columns.rs

@@ -180,7 +180,7 @@ fn detect_columns(
         })
         .into_pipeline_data(ctrlc))
     } else {
-        Ok(PipelineData::new(name_span))
+        Ok(PipelineData::empty())
     }
 }
 

crates/nu-command/src/strings/encode_decode/decode.rs

@@ -66,7 +66,7 @@ documentation link at https://docs.rs/encoding_rs/0.8.28/encoding_rs/#statics"#
         let encoding: Spanned<String> = call.req(engine_state, stack, 0)?;
 
         match input {
-            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(call.head)),
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 ..

crates/nu-command/src/strings/encode_decode/encode.rs

@@ -66,7 +66,7 @@ documentation link at https://docs.rs/encoding_rs/0.8.28/encoding_rs/#statics"#
         let encoding: Spanned<String> = call.req(engine_state, stack, 0)?;
 
         match input {
-            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::new(call.head)),
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 ..

crates/nu-command/src/system/benchmark.rs

@@ -44,7 +44,7 @@ impl Command for Benchmark {
             engine_state,
             &mut stack,
             block,
-            PipelineData::new(call.head),
+            PipelineData::empty(),
             redirect_stdout,
             redirect_stderr,
         )?

crates/nu-command/src/viewers/griddle.rs

@@ -88,7 +88,7 @@ prints out the list properly."#
                         use_grid_icons,
                     )?)
                 } else {
-                    Ok(PipelineData::new(call.head))
+                    Ok(PipelineData::empty())
                 }
             }
             PipelineData::ListStream(stream, ..) => {
@@ -106,7 +106,7 @@ prints out the list properly."#
                     )?)
                 } else {
                     // dbg!(data);
-                    Ok(PipelineData::new(call.head))
+                    Ok(PipelineData::empty())
                 }
             }
             PipelineData::Value(Value::Record { cols, vals, .. }, ..) => {

crates/nu-command/tests/commands/update.rs

@@ -43,7 +43,7 @@ fn sets_the_column_from_a_block_full_stream_output() {
     let actual = nu!(
         cwd: "tests/fixtures/formats", pipeline(
         r#"
-            wrap content
+            {content: null}
             | update content { open --raw cargo_sample.toml | lines | first 5 }
             | get content.1
             | str contains "nu"
@@ -58,7 +58,7 @@ fn sets_the_column_from_a_subexpression() {
     let actual = nu!(
         cwd: "tests/fixtures/formats", pipeline(
         r#"
-            wrap content
+            {content: null}
             | update content (open --raw cargo_sample.toml | lines | first 5)
             | get content.1
             | str contains "nu"

crates/nu-command/tests/commands/upsert.rs

@@ -43,7 +43,7 @@ fn sets_the_column_from_a_block_full_stream_output() {
     let actual = nu!(
         cwd: "tests/fixtures/formats", pipeline(
         r#"
-            wrap content
+            {content: null}
             | upsert content { open --raw cargo_sample.toml | lines | first 5 }
             | get content.1
             | str contains "nu"
@@ -58,7 +58,7 @@ fn sets_the_column_from_a_subexpression() {
     let actual = nu!(
         cwd: "tests/fixtures/formats", pipeline(
         r#"
-            wrap content
+            {content: null}
             | upsert content (open --raw cargo_sample.toml | lines | first 5)
             | get content.1
             | str contains "nu"

crates/nu-engine/src/env.rs

@@ -350,7 +350,7 @@ fn get_converted_value(
                     engine_state,
                     &mut stack,
                     block,
-                    PipelineData::new(val_span),
+                    PipelineData::new_with_metadata(None, val_span),
                     true,
                     true,
                 );

crates/nu-engine/src/eval.rs

@@ -339,10 +339,7 @@ pub fn eval_expression(
         }
         Expr::Call(call) => {
             // FIXME: protect this collect with ctrl-c
-            Ok(
-                eval_call(engine_state, stack, call, PipelineData::new(call.head))?
-                    .into_value(call.head),
-            )
+            Ok(eval_call(engine_state, stack, call, PipelineData::empty())?.into_value(call.head))
         }
         Expr::ExternalCall(head, args, is_subexpression) => {
             let span = head.span;
@@ -352,7 +349,7 @@ pub fn eval_expression(
                 stack,
                 head,
                 args,
-                PipelineData::new(span),
+                PipelineData::empty(),
                 false,
                 false,
                 *is_subexpression,
@@ -536,7 +533,7 @@ pub fn eval_expression(
 
             // FIXME: protect this collect with ctrl-c
             Ok(
-                eval_subexpression(engine_state, stack, block, PipelineData::new(expr.span))?
+                eval_subexpression(engine_state, stack, block, PipelineData::empty())?
                     .into_value(expr.span),
             )
         }
@@ -1087,14 +1084,28 @@ pub fn eval_block(
 
                     match engine_state.find_decl("table".as_bytes(), &[]) {
                         Some(decl_id) => {
-                            let table = engine_state.get_decl(decl_id).run(
-                                engine_state,
-                                stack,
-                                &Call::new(Span::new(0, 0)),
-                                input,
-                            )?;
+                            let table = engine_state.get_decl(decl_id);
 
-                            print_or_return(table, config)?;
+                            if let Some(block_id) = table.get_block_id() {
+                                let block = engine_state.get_block(block_id);
+                                eval_block(
+                                    engine_state,
+                                    stack,
+                                    block,
+                                    input,
+                                    redirect_stdout,
+                                    redirect_stderr,
+                                )?;
+                            } else {
+                                let table = table.run(
+                                    engine_state,
+                                    stack,
+                                    &Call::new(Span::new(0, 0)),
+                                    input,
+                                )?;
+
+                                print_or_return(table, config)?;
+                            }
                         }
                         None => {
                             print_or_return(input, config)?;
@@ -1103,7 +1114,7 @@ pub fn eval_block(
                 }
             }
 
-            input = PipelineData::new(Span::unknown())
+            input = PipelineData::empty()
         }
     }
 

crates/nu-explore/src/nu_common/value.rs

@@ -5,6 +5,7 @@ use super::NuSpan;
 
 pub fn collect_pipeline(input: PipelineData) -> (Vec<String>, Vec<Vec<Value>>) {
     match input {
+        PipelineData::Empty => (vec![], vec![]),
         PipelineData::Value(value, ..) => collect_input(value),
         PipelineData::ListStream(mut stream, ..) => {
             let mut records = vec![];

crates/nu-protocol/src/pipeline_data.rs

@@ -53,6 +53,7 @@ pub enum PipelineData {
         metadata: Option<PipelineMetadata>,
         trim_end_newline: bool,
     },
+    Empty,
 }
 
 #[derive(Debug, Clone)]
@@ -67,19 +68,20 @@ pub enum DataSource {
 }
 
 impl PipelineData {
-    pub fn new(span: Span) -> PipelineData {
-        PipelineData::Value(Value::Nothing { span }, None)
-    }
-
     pub fn new_with_metadata(metadata: Option<PipelineMetadata>, span: Span) -> PipelineData {
         PipelineData::Value(Value::Nothing { span }, metadata)
     }
 
+    pub fn empty() -> PipelineData {
+        PipelineData::Empty
+    }
+
     pub fn metadata(&self) -> Option<PipelineMetadata> {
         match self {
             PipelineData::ListStream(_, x) => x.clone(),
             PipelineData::ExternalStream { metadata: x, .. } => x.clone(),
             PipelineData::Value(_, x) => x.clone(),
+            PipelineData::Empty => None,
         }
     }
 
@@ -88,6 +90,7 @@ impl PipelineData {
             PipelineData::ListStream(_, x) => *x = metadata,
             PipelineData::ExternalStream { metadata: x, .. } => *x = metadata,
             PipelineData::Value(_, x) => *x = metadata,
+            PipelineData::Empty => {}
         }
 
         self
@@ -95,6 +98,7 @@ impl PipelineData {
 
     pub fn is_nothing(&self) -> bool {
         matches!(self, PipelineData::Value(Value::Nothing { .. }, ..))
+            || matches!(self, PipelineData::Empty)
     }
 
     /// PipelineData doesn't always have a Span, but we can try!
@@ -103,11 +107,13 @@ impl PipelineData {
             PipelineData::ListStream(..) => None,
             PipelineData::ExternalStream { span, .. } => Some(*span),
             PipelineData::Value(v, _) => v.span().ok(),
+            PipelineData::Empty => None,
         }
     }
 
     pub fn into_value(self, span: Span) -> Value {
         match self {
+            PipelineData::Empty => Value::nothing(span),
             PipelineData::Value(Value::Nothing { .. }, ..) => Value::nothing(span),
             PipelineData::Value(v, ..) => v,
             PipelineData::ListStream(s, ..) => Value::List {
@@ -202,6 +208,7 @@ impl PipelineData {
 
     pub fn collect_string(self, separator: &str, config: &Config) -> Result<String, ShellError> {
         match self {
+            PipelineData::Empty => Ok(String::new()),
             PipelineData::Value(v, ..) => Ok(v.into_string(separator, config)),
             PipelineData::ListStream(s, ..) => Ok(s.into_string(separator, config)),
             PipelineData::ExternalStream { stdout: None, .. } => Ok(String::new()),
@@ -238,6 +245,7 @@ impl PipelineData {
         span: Span,
     ) -> Result<(String, Option<PipelineMetadata>), ShellError> {
         match self {
+            PipelineData::Empty => Ok((String::new(), None)),
             PipelineData::Value(Value::String { val, .. }, metadata) => Ok((val, metadata)),
             PipelineData::Value(val, _) => {
                 Err(ShellError::TypeMismatch("string".into(), val.span()?))
@@ -306,10 +314,9 @@ impl PipelineData {
             PipelineData::Value(Value::List { vals, .. }, ..) => {
                 Ok(vals.into_iter().map(f).into_pipeline_data(ctrlc))
             }
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::ListStream(stream, ..) => Ok(stream.map(f).into_pipeline_data(ctrlc)),
-            PipelineData::ExternalStream { stdout: None, .. } => {
-                Ok(PipelineData::new(Span::unknown()))
-            }
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 trim_end_newline,
@@ -359,15 +366,14 @@ impl PipelineData {
         F: FnMut(Value) -> U + 'static + Send,
     {
         match self {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::Value(Value::List { vals, .. }, ..) => {
                 Ok(vals.into_iter().flat_map(f).into_pipeline_data(ctrlc))
             }
             PipelineData::ListStream(stream, ..) => {
                 Ok(stream.flat_map(f).into_pipeline_data(ctrlc))
             }
-            PipelineData::ExternalStream { stdout: None, .. } => {
-                Ok(PipelineData::new(Span::unknown()))
-            }
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::Empty),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 trim_end_newline,
@@ -414,13 +420,12 @@ impl PipelineData {
         F: FnMut(&Value) -> bool + 'static + Send,
     {
         match self {
+            PipelineData::Empty => Ok(PipelineData::Empty),
             PipelineData::Value(Value::List { vals, .. }, ..) => {
                 Ok(vals.into_iter().filter(f).into_pipeline_data(ctrlc))
             }
             PipelineData::ListStream(stream, ..) => Ok(stream.filter(f).into_pipeline_data(ctrlc)),
-            PipelineData::ExternalStream { stdout: None, .. } => {
-                Ok(PipelineData::new(Span::unknown()))
-            }
+            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::Empty),
             PipelineData::ExternalStream {
                 stdout: Some(stream),
                 trim_end_newline,
@@ -440,7 +445,7 @@ impl PipelineData {
                     if f(&v) {
                         Ok(v.into_pipeline_data())
                     } else {
-                        Ok(PipelineData::new(collected.span))
+                        Ok(PipelineData::new_with_metadata(None, collected.span))
                     }
                 } else {
                     let v = Value::Binary {
@@ -451,7 +456,7 @@ impl PipelineData {
                     if f(&v) {
                         Ok(v.into_pipeline_data())
                     } else {
-                        Ok(PipelineData::new(collected.span))
+                        Ok(PipelineData::new_with_metadata(None, collected.span))
                     }
                 }
             }
@@ -636,6 +641,7 @@ impl Iterator for PipelineIterator {
 
     fn next(&mut self) -> Option<Self::Item> {
         match &mut self.0 {
+            PipelineData::Empty => None,
             PipelineData::Value(Value::Nothing { .. }, ..) => None,
             PipelineData::Value(v, ..) => Some(std::mem::take(v)),
             PipelineData::ListStream(stream, ..) => stream.next(),

src/config_files.rs

@@ -3,7 +3,7 @@ use nu_cli::{eval_config_contents, eval_source, report_error};
 use nu_parser::ParseError;
 use nu_path::canonicalize_with;
 use nu_protocol::engine::{EngineState, Stack, StateWorkingSet};
-use nu_protocol::{PipelineData, Span, Spanned};
+use nu_protocol::{PipelineData, Spanned};
 use nu_utils::{get_default_config, get_default_env};
 use std::fs::File;
 use std::io::Write;
@@ -128,7 +128,7 @@ pub(crate) fn read_default_env_file(engine_state: &mut EngineState, stack: &mut
         stack,
         config_file.as_bytes(),
         "default_env.nu",
-        PipelineData::new(Span::new(0, 0)),
+        PipelineData::empty(),
     );
 
     info!("read_config_file {}:{}:{}", file!(), line!(), column!());
@@ -164,7 +164,7 @@ fn eval_default_config(
         } else {
             "default_config.nu"
         },
-        PipelineData::new(Span::new(0, 0)),
+        PipelineData::empty(),
     );
 
     // Merge the environment in case env vars changed in the config

src/main.rs

@@ -22,8 +22,8 @@ use nu_path::canonicalize_with;
 use nu_protocol::{
     ast::{Call, Expr, Expression, PipelineElement},
     engine::{Command, EngineState, Stack, StateWorkingSet},
-    Category, Example, IntoPipelineData, PipelineData, RawStream, ShellError, Signature, Span,
-    Spanned, SyntaxShape, Value,
+    Category, Example, IntoPipelineData, PipelineData, RawStream, ShellError, Signature, Spanned,
+    SyntaxShape, Value,
 };
 use nu_utils::stdout_write_all_and_flush;
 use std::{
@@ -323,7 +323,7 @@ fn main() -> Result<()> {
                     trim_end_newline: false,
                 }
             } else {
-                PipelineData::new(Span::new(0, 0))
+                PipelineData::empty()
             };
 
             info!("redirect_stdin {}:{}:{}", file!(), line!(), column!());

src/test_bins.rs

@@ -220,7 +220,7 @@ pub fn nu_repl() {
             outcome_err(&engine_state, &err);
         }
 
-        let input = PipelineData::new(Span::test_data());
+        let input = PipelineData::empty();
         let config = engine_state.get_config();
 
         match eval_block(&engine_state, &mut stack, &block, input, false, false) {