add view blocks command (#14610)

# Description

This PR is meant to add another nushell introspection/debug command,
`view blocks`. This command shows what is in the EngineState's memory
that is parsed and stored as blocks. Blocks may continue to grow as you
use the repl.
 

![image](https://github.com/user-attachments/assets/8a19fd56-ef15-4993-9700-a51eb8eaec7f)

# User-Facing Changes
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# Tests + Formatting
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> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
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crates/nu-command/src/debug/mod.rs

@@ -10,6 +10,7 @@ mod metadata_set;
 mod profile;
 mod timeit;
 mod view;
+mod view_blocks;
 mod view_files;
 mod view_ir;
 mod view_source;
@@ -27,6 +28,7 @@ pub use metadata_set::MetadataSet;
 pub use profile::DebugProfile;
 pub use timeit::TimeIt;
 pub use view::View;
+pub use view_blocks::ViewBlocks;
 pub use view_files::ViewFiles;
 pub use view_ir::ViewIr;
 pub use view_source::ViewSource;

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

@@ -0,0 +1,71 @@
+use nu_engine::command_prelude::*;
+
+#[derive(Clone)]
+pub struct ViewBlocks;
+
+impl Command for ViewBlocks {
+    fn name(&self) -> &str {
+        "view blocks"
+    }
+
+    fn description(&self) -> &str {
+        "View the blocks registered in nushell's EngineState memory."
+    }
+
+    fn extra_description(&self) -> &str {
+        "These are blocks parsed and loaded at runtime as well as any blocks that accumulate in the repl."
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("view blocks")
+            .input_output_types(vec![(
+                Type::Nothing,
+                Type::Table(
+                    [
+                        ("block_id".into(), Type::Int),
+                        ("content".into(), Type::String),
+                        ("start".into(), Type::Int),
+                        ("end".into(), Type::Int),
+                    ]
+                    .into(),
+                ),
+            )])
+            .category(Category::Debug)
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let mut records = vec![];
+
+        for block_id in 0..engine_state.num_blocks() {
+            let block = engine_state.get_block(nu_protocol::BlockId::new(block_id));
+
+            if let Some(span) = block.span {
+                let contents_bytes = engine_state.get_span_contents(span);
+                let contents_string = String::from_utf8_lossy(contents_bytes);
+                let cur_rec = record! {
+                    "block_id" => Value::int(block_id as i64, span),
+                    "content" => Value::string(contents_string.trim().to_string(), span),
+                    "start" => Value::int(span.start as i64, span),
+                    "end" => Value::int(span.end as i64, span),
+                };
+                records.push(Value::record(cur_rec, span));
+            }
+        }
+
+        Ok(Value::list(records, call.head).into_pipeline_data())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "View the blocks registered in Nushell's EngineState memory",
+            example: r#"view blocks"#,
+            result: None,
+        }]
+    }
+}

crates/nu-command/src/default_context.rs

@@ -161,6 +161,7 @@ pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {
             MetadataSet,
             TimeIt,
             View,
+            ViewBlocks,
             ViewFiles,
             ViewIr,
             ViewSource,