Make timeit work with command calls (#8594)

# Description

Allows `timeit` to also run commands directly, eg) `timeit ls -la`

# User-Facing Changes

Additional capabilities to `timeit`.

# 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

> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```

# 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/debug/timeit.rs

@@ -1,7 +1,7 @@
-use nu_engine::{eval_block, CallExt};
+use nu_engine::{eval_block, eval_expression_with_input};
 use nu_protocol::{
     ast::Call,
-    engine::{Block, Command, EngineState, Stack},
+    engine::{Command, EngineState, Stack},
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Type,
     Value,
 };
@@ -21,7 +21,11 @@ impl Command for TimeIt {
 
     fn signature(&self) -> nu_protocol::Signature {
         Signature::build("timeit")
-            .required("block", SyntaxShape::Block, "the block to run")
+            .required(
+                "command",
+                SyntaxShape::OneOf(vec![SyntaxShape::Block, SyntaxShape::Expression]),
+                "the command or block to run",
+            )
             .input_output_types(vec![
                 (Type::Any, Type::Duration),
                 (Type::Nothing, Type::Duration),
@@ -41,37 +45,36 @@ impl Command for TimeIt {
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        let capture_block: Block = call.req(engine_state, stack, 0)?;
+        let command_to_run = call.positional_nth(0);
-        let block = engine_state.get_block(capture_block.block_id);
-
-        let redirect_stdout = call.redirect_stdout;
-        let redirect_stderr = call.redirect_stderr;
-
-        // let mut stack = stack.captures_to_stack(&capture_block.captures);
-
-        // In order to provide the pipeline as a positional, it must be converted into a value.
-        // But because pipelines do not have Clone, this one has to be cloned as a value
-        // and then converted back into a pipeline for eval_block().
-        // So, the metadata must be saved here and restored at that point.
-        let input_metadata = input.metadata();
-        let input_val = input.into_value(call.head);
-
-        if let Some(var) = block.signature.get_positional(0) {
-            if let Some(var_id) = &var.var_id {
-                stack.add_var(*var_id, input_val.clone());
-            }
-        }
 
         // Get the start time after all other computation has been done.
         let start_time = Instant::now();
+
+        if let Some(command_to_run) = command_to_run {
+            if let Some(block_id) = command_to_run.as_block() {
+                let block = engine_state.get_block(block_id);
                 eval_block(
                     engine_state,
                     stack,
                     block,
-            input_val.into_pipeline_data_with_metadata(input_metadata),
+                    input,
-            redirect_stdout,
+                    call.redirect_stdout,
-            redirect_stderr,
+                    call.redirect_stderr,
                 )?
+            } else {
+                eval_expression_with_input(
+                    engine_state,
+                    stack,
+                    command_to_run,
+                    input,
+                    call.redirect_stdout,
+                    call.redirect_stderr,
+                )
+                .map(|res| res.0)?
+            }
+        } else {
+            PipelineData::empty()
+        }
         .into_value(call.head);
 
         let end_time = Instant::now();
@@ -96,6 +99,11 @@ impl Command for TimeIt {
                 example: "http get https://www.nushell.sh/book/ | timeit { split chars }",
                 result: None,
             },
+            Example {
+                description: "Times a command invocation",
+                example: "timeit ls -la",
+                result: None,
+            },
         ]
     }
 }