Rename main to script name when running scripts (#9948)

# Description

This PR does three related changes:

* Keeps the originally declared name in help outputs.
* Updates the name of the commands called `main` in the user script to
the name of the script.
* Fixes the source of signature information in multiple places. This
allows scripts to have more complete help output.

Combined, the above allow the user to see the script name in the help
output of scripts, like so:


![image](https://github.com/nushell/nushell/assets/547158/741d192c-0a39-45a7-8f36-3a0dc8eeae2b)

NOTE: You still declare and call the definition `main`, so from inside
the script `main` is still the correct name. But multiple folks agreed
that seeing `main` in the script help was confusing, so this PR changes
that.

# User-Facing Changes

One potential minor breaking change is that module renames will be shown
as their originally defined name rather than the renamed name. I believe
this to be a better default.

# Tests + Formatting
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- `cargo fmt --all -- --check` to check standard code formatting (`cargo
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crates/nu-cli/src/eval_file.rs

@@ -2,6 +2,7 @@ use crate::util::eval_source;
 use log::info;
 use log::trace;
 use miette::{IntoDiagnostic, Result};
+use nu_engine::eval_block_with_early_return;
 use nu_engine::{convert_env_values, current_dir};
 use nu_parser::parse;
 use nu_path::canonicalize_with;
@@ -98,23 +99,59 @@ pub fn evaluate_file(
         Value::string(file_path.to_string_lossy(), Span::unknown()),
     );
 
+    let source_filename = file_path
+        .file_name()
+        .expect("internal error: script missing filename");
+
     let mut working_set = StateWorkingSet::new(engine_state);
     trace!("parsing file: {}", file_path_str);
-    let _ = parse(&mut working_set, Some(file_path_str), &file, false);
+    let block = parse(&mut working_set, Some(file_path_str), &file, false);
 
-    if working_set.find_decl(b"main").is_some() {
+    for block in &mut working_set.delta.blocks {
+        if block.signature.name == "main" {
+            block.signature.name = source_filename.to_string_lossy().to_string();
+        } else if block.signature.name.starts_with("main ") {
+            block.signature.name = source_filename.to_string_lossy().to_string()
+                + " "
+                + &String::from_utf8_lossy(&block.signature.name.as_bytes()[5..]);
+        }
+    }
+
+    let _ = engine_state.merge_delta(working_set.delta);
+
+    if engine_state.find_decl(b"main", &[]).is_some() {
         let args = format!("main {}", args.join(" "));
 
-        if !eval_source(
+        let pipeline_data = eval_block_with_early_return(
             engine_state,
             stack,
-            &file,
-            file_path_str,
+            &block,
             PipelineData::empty(),
-            true,
-        ) {
+            false,
+            false,
+        )
+        .unwrap_or_else(|e| {
+            let working_set = StateWorkingSet::new(engine_state);
+            report_error(&working_set, &e);
             std::process::exit(1);
+        });
+
+        let result = pipeline_data.print(engine_state, stack, true, false);
+
+        match result {
+            Err(err) => {
+                let working_set = StateWorkingSet::new(engine_state);
+
+                report_error(&working_set, &err);
+                std::process::exit(1);
+            }
+            Ok(exit_code) => {
+                if exit_code != 0 {
+                    std::process::exit(exit_code as i32);
+                }
+            }
         }
+
         if !eval_source(
             engine_state,
             stack,

crates/nu-command/src/help/help_commands.rs

@@ -127,13 +127,12 @@ fn build_help_commands(engine_state: &EngineState, span: Span) -> Vec<Value> {
     let commands = engine_state.get_decls_sorted(false);
     let mut found_cmds_vec = Vec::new();
 
-    for (name_bytes, decl_id) in commands {
+    for (_, decl_id) in commands {
         let mut cols = vec![];
         let mut vals = vec![];
 
-        let name = String::from_utf8_lossy(&name_bytes).to_string();
         let decl = engine_state.get_decl(decl_id);
-        let sig = decl.signature().update_from_command(name, decl.borrow());
+        let sig = decl.signature().update_from_command(decl.borrow());
 
         let key = sig.name;
         let usage = sig.usage;

crates/nu-engine/src/eval.rs

@@ -38,7 +38,7 @@ pub fn eval_call(
     let decl = engine_state.get_decl(call.decl_id);
 
     if !decl.is_known_external() && call.named_iter().any(|(flag, _, _)| flag.item == "help") {
-        let mut signature = decl.signature();
+        let mut signature = engine_state.get_signature(decl);
         signature.usage = decl.usage().to_string();
         signature.extra_usage = decl.extra_usage().to_string();
 

crates/nu-engine/src/scope.rs

@@ -534,12 +534,11 @@ impl<'e, 's> ScopeData<'e, 's> {
 
     pub fn collect_aliases(&self, span: Span) -> Vec<Value> {
         let mut aliases = vec![];
-        for (name_bytes, decl_id) in self.engine_state.get_decls_sorted(false) {
+        for (_, decl_id) in self.engine_state.get_decls_sorted(false) {
             if self.visibility.is_decl_id_visible(&decl_id) {
                 let decl = self.engine_state.get_decl(decl_id);
                 if let Some(alias) = decl.as_alias() {
-                    let name = String::from_utf8_lossy(&name_bytes).to_string();
-                    let sig = decl.signature().update_from_command(name, decl.borrow());
+                    let sig = decl.signature().update_from_command(decl.borrow());
                     let key = sig.name;
 
                     aliases.push(Value::Record {

crates/nu-protocol/src/engine/engine_state.rs

@@ -783,16 +783,22 @@ impl EngineState {
         decls.into_iter()
     }
 
+    #[allow(clippy::borrowed_box)]
+    pub fn get_signature(&self, decl: &Box<dyn Command>) -> Signature {
+        if let Some(block_id) = decl.get_block_id() {
+            *self.blocks[block_id].signature.clone()
+        } else {
+            decl.signature()
+        }
+    }
+
     /// Get signatures of all commands within scope.
     pub fn get_signatures(&self, include_hidden: bool) -> Vec<Signature> {
         self.get_decls_sorted(include_hidden)
-            .map(|(name_bytes, id)| {
+            .map(|(_, id)| {
                 let decl = self.get_decl(id);
-                // the reason to create the name this way is because the command could be renamed
-                // during module imports but the signature still contains the old name
-                let name = String::from_utf8_lossy(&name_bytes).to_string();
 
-                (*decl).signature().update_from_command(name, decl.borrow())
+                self.get_signature(decl).update_from_command(decl.borrow())
             })
             .collect()
     }
@@ -807,13 +813,10 @@ impl EngineState {
         include_hidden: bool,
     ) -> Vec<(Signature, Vec<Example>, bool, bool, bool)> {
         self.get_decls_sorted(include_hidden)
-            .map(|(name_bytes, id)| {
+            .map(|(_, id)| {
                 let decl = self.get_decl(id);
-                // the reason to create the name this way is because the command could be renamed
-                // during module imports but the signature still contains the old name
-                let name = String::from_utf8_lossy(&name_bytes).to_string();
 
-                let signature = (*decl).signature().update_from_command(name, decl.borrow());
+                let signature = self.get_signature(decl).update_from_command(decl.borrow());
 
                 (
                     signature,

crates/nu-protocol/src/plugin_signature.rs

@@ -48,8 +48,8 @@ impl PluginSignature {
     }
 
     /// Update signature's fields from a Command trait implementation
-    pub fn update_from_command(mut self, name: String, command: &dyn Command) -> PluginSignature {
-        self.sig = self.sig.update_from_command(name, command);
+    pub fn update_from_command(mut self, command: &dyn Command) -> PluginSignature {
+        self.sig = self.sig.update_from_command(command);
         self
     }
 

crates/nu-protocol/src/signature.rs

@@ -237,8 +237,7 @@ impl Signature {
     }
 
     /// Update signature's fields from a Command trait implementation
-    pub fn update_from_command(mut self, name: String, command: &dyn Command) -> Signature {
-        self.name = name;
+    pub fn update_from_command(mut self, command: &dyn Command) -> Signature {
         self.search_terms = command
             .search_terms()
             .into_iter()