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<!-- if this PR closes one or more issues, you can automatically link the PR with them by using one of the [*linking keywords*](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword), e.g. - this PR should close #xxxx - fixes #xxxx you can also mention related issues, PRs or discussions! --> # Description <!-- Thank you for improving Nushell. Please, check our [contributing guide](../CONTRIBUTING.md) and talk to the core team before making major changes. Description of your pull request goes here. **Provide examples and/or screenshots** if your changes affect the user experience. --> This PR adds a new evaluator path with callbacks to a mutable trait object implementing a Debugger trait. The trait object can do anything, e.g., profiling, code coverage, step debugging. Currently, entering/leaving a block and a pipeline element is marked with callbacks, but more callbacks can be added as necessary. Not all callbacks need to be used by all debuggers; unused ones are simply empty calls. A simple profiler is implemented as a proof of concept. The debugging support is implementing by making `eval_xxx()` functions generic depending on whether we're debugging or not. This has zero computational overhead, but makes the binary slightly larger (see benchmarks below). `eval_xxx()` variants called from commands (like `eval_block_with_early_return()` in `each`) are chosen with a dynamic dispatch for two reasons: to not grow the binary size due to duplicating the code of many commands, and for the fact that it isn't possible because it would make Command trait objects object-unsafe. In the future, I hope it will be possible to allow plugin callbacks such that users would be able to implement their profiler plugins instead of having to recompile Nushell. [DAP](https://microsoft.github.io/debug-adapter-protocol/) would also be interesting to explore. Try `help debug profile`. ## Screenshots Basic output:  To profile with more granularity, increase the profiler depth (you'll see that repeated `is-windows` calls take a large chunk of total time, making it a good candidate for optimizing):  ## Benchmarks ### Binary size Binary size increase vs. main: **+40360 bytes**. _(Both built with `--release --features=extra,dataframe`.)_ ### Time ```nushell # bench_debug.nu use std bench let test = { 1..100 | each { ls | each {|row| $row.name | str length } } | flatten | math avg } print 'debug:' let res2 = bench { debug profile $test } --pretty print $res2 ``` ```nushell # bench_nodebug.nu use std bench let test = { 1..100 | each { ls | each {|row| $row.name | str length } } | flatten | math avg } print 'no debug:' let res1 = bench { do $test } --pretty print $res1 ``` `cargo run --release -- bench_debug.nu` is consistently 1--2 ms slower than `cargo run --release -- bench_nodebug.nu` due to the collection overhead + gathering the report. This is expected. When gathering more stuff, the overhead is obviously higher. `cargo run --release -- bench_nodebug.nu` vs. `nu bench_nodebug.nu` I didn't measure any difference. Both benchmarks report times between 97 and 103 ms randomly, without one being consistently higher than the other. This suggests that at least in this particular case, when not running any debugger, there is no runtime overhead. ## API changes This PR adds a generic parameter to all `eval_xxx` functions that forces you to specify whether you use the debugger. You can resolve it in two ways: * Use a provided helper that will figure it out for you. If you wanted to use `eval_block(&engine_state, ...)`, call `let eval_block = get_eval_block(&engine_state); eval_block(&engine_state, ...)` * If you know you're in an evaluation path that doesn't need debugger support, call `eval_block::<WithoutDebug>(&engine_state, ...)` (this is the case of hooks, for example). I tried to add more explanation in the docstring of `debugger_trait.rs`. ## TODO - [x] Better profiler output to reduce spam of iterative commands like `each` - [x] Resolve `TODO: DEBUG` comments - [x] Resolve unwraps - [x] Add doc comments - [x] Add usage and extra usage for `debug profile`, explaining all columns # User-Facing Changes <!-- List of all changes that impact the user experience here. This helps us keep track of breaking changes. --> Hopefully 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` to check that you're using the standard code style - `cargo test --workspace` to check that all tests pass (on Windows make sure to [enable developer mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging)) - `cargo run -- -c "use std testing; testing run-tests --path crates/nu-std"` to run the tests for the standard library > **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. --> |
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