move ast command to the debug group (#8077)

# Description

This PR tweaks how `ast` works a tiny bit by outputting values in stead
of eprintln!'s. It also moves the `ast` command into the folder with the
rest of the debug commands and changes the category to debug.

I started adding some tests but couldn't figure out a good way to do it
since every `ast` command contains spans that will be different on each
invocation.

# User-Facing Changes



# 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-command/src/core_commands/mod.rs

@@ -1,5 +1,4 @@
 mod alias;
-mod ast;
 mod break_;
 mod commandline;
 mod const_;
@@ -39,7 +38,6 @@ mod version;
 mod while_;
 
 pub use alias::Alias;
-pub use ast::Ast;
 pub use break_::Break;
 pub use commandline::Commandline;
 pub use const_::Const;

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

@@ -3,8 +3,8 @@ use nu_parser::parse;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack, StateWorkingSet},
-    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type,
-    Value,
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Spanned, SyntaxShape,
+    Type, Value,
 };
 
 #[derive(Clone)]
@@ -21,13 +21,14 @@ impl Command for Ast {
 
     fn signature(&self) -> Signature {
         Signature::build("ast")
-            .input_output_types(vec![(Type::Nothing, Type::Nothing)])
+            .input_output_types(vec![(Type::String, Type::Record(vec![]))])
             .required(
                 "pipeline",
                 SyntaxShape::String,
                 "the pipeline to print the ast for",
             )
-            .category(Category::Core)
+            .allow_variants_without_examples(true)
+            .category(Category::Debug)
     }
 
     fn run(
@@ -40,10 +41,22 @@ impl Command for Ast {
         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: {output:#?}\nerror: {err:#?}");
-
-        Ok(PipelineData::empty())
+        let (block_output, error_output) =
+            parse(&mut working_set, None, pipeline.item.as_bytes(), false, &[]);
+        let block_value = Value::String {
+            val: format!("{block_output:#?}"),
+            span: pipeline.span,
+        };
+        let error_value = Value::String {
+            val: format!("{error_output:#?}"),
+            span: pipeline.span,
+        };
+        let output_record = Value::Record {
+            cols: vec!["block".to_string(), "error".to_string()],
+            vals: vec![block_value, error_value],
+            span: pipeline.span,
+        };
+        Ok(output_record.into_pipeline_data())
     }
 
     fn examples(&self) -> Vec<Example> {
@@ -51,17 +64,17 @@ impl Command for Ast {
             Example {
                 description: "Print the ast of a string",
                 example: "ast 'hello'",
-                result: Some(Value::nothing(Span::test_data())),
+                result: None,
             },
             Example {
                 description: "Print the ast of a pipeline",
                 example: "ast 'ls | where name =~ README'",
-                result: Some(Value::nothing(Span::test_data())),
+                result: None,
             },
             Example {
                 description: "Print the ast of a pipeline with an error",
                 example: "ast 'for x in 1..10 { echo $x '",
-                result: Some(Value::nothing(Span::test_data())),
+                result: None,
             },
         ]
     }

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

@@ -1,3 +1,4 @@
+mod ast;
 mod debug_;
 mod explain;
 mod inspect;
@@ -10,6 +11,7 @@ mod view_files;
 mod view_source;
 mod view_span;
 
+pub use ast::Ast;
 pub use debug_::Debug;
 pub use explain::Explain;
 pub use inspect::Inspect;

crates/nu-command/src/default_context.rs

@@ -29,7 +29,6 @@ pub fn create_default_context() -> EngineState {
         // Core
         bind_command! {
             Alias,
-            Ast,
             Break,
             Commandline,
             Const,
@@ -178,6 +177,7 @@ pub fn create_default_context() -> EngineState {
 
         // Debug
         bind_command! {
+            Ast,
             Debug,
             Explain,
             Inspect,