nushell/crates/nu-std/std/mod.nu

29 lines
509 B
Text
Raw Normal View History

# std.nu, `used` to load all standard library components
Improves startup time when using std-lib (#13842) Updated summary for commit [612e0e2](https://github.com/nushell/nushell/pull/13842/commits/612e0e21602f55092bc121bfd07f7c3bf5119e4f) - While folks are welcome to read through the entire comments, the core information is summarized here. # Description This PR drastically improves startup times of Nushell by only parsing a single submodule of the Standard Library that provides the `banner` and `pwd` commands. All other Standard Library commands and submodules are parsed when imported by the user. This cuts startup times by more than 60%. At the moment, we have stopped adding to `std-lib` because every addition adds a small amount to the Nushell startup time. With this change, we should once again be able to allow new functionality to be added to the Standard Library without it impacting `nu` startup times. # User-Facing Changes * Nushell now starts about 60% faster * Breaking change: The `dirs` (Shells) aliases will return a warning message that it will not be auto-loaded in the following release, along with instructions on how to restore it (and disable the message) * The `use std <submodule> *` syntax is available for convenience, but should be avoided in scripts as it parses the entire `std` module and all other submodules and places it in scope. The correct syntax to *just* load a submodule is `use std/<submodule> *` (asterisk optional). The slash is important. This will be documented. * `use std *` can be used for convenience to load all of the library but still incurs the full loading-time. * `std/dirs`: Semi-breaking change. The `dirs` command replaces the `show` command. This is more in line with the directory-stack functionality found in other shells. Existing users will not be impacted by this as the alias (`shells`) remains the same. * Breaking-change: Technically a breaking change, but probably only impacts maintainers of `std`. The virtual path for the standard library has changed. It could previously be imported using its virtual path (and technically, this would have been the correct way to do it): ```nu use NU_STDLIB_VIRTUAL_DIR/std ``` The path is now simply `std/`: ```nu use std ``` All submodules have moved accordingly. # Timings Comparisons below were made: * In a temporary, clean config directory using `$env.XDG_CONFIG_HOME = (mktemp -d)`. * `nu` was run with a release build * `nu` was run one time to generate the default `config.nu` (etc.) files - Otherwise timings would include the user-prompt * The shell was exited and then restarted several times to get timing samples (Note: Old timings based on 0.97 rather than 0.98, but in the range of being accurate) | Scenario | `$nu.startup-time` | | --- | --- | | 0.97.2 ([aaaab8e](https://github.com/nushell/nushell/commit/aaaab8e070c644a87bbd7682099e3fe9e6a4b42a)) Without this PR | 23ms - 24ms | | This PR with deprecated commands | 9ms - <11ms | | This PR after deprecated commands are removed in following release | 8ms - <10ms | | Final PR (remove deprecated), using `--no-std-lib` | 6.1ms to 6.4ms | | Final PR (remove deprecated), using `--no-config-file` | 3.1ms - 3.6ms | | Final PR (remove deprecated), using `--no-config-file --no-std-lib` | 1ms - 1.5ms | *These last two timings point to the opportunity for further optimization (see comment in thread below (will link once I write it).* # Implementation details for future maintenance * `use std banner` is a ridiculously deceptive call. That call parses and imports *all* of `std` into scope. Simply replacing it with `use std/core *` is essentially what saves ~14-15ms. This *only* imports the submodule with the `banner` and `pwd` commands. * From the code-comments, the reason that `NU_STDLIB_VIRTUAL_DIR` was used as a prefix was so that there wouldn't be an issue if a user had a `./std/mod.nu` in the current directory. This does **not** appear to be an issue. After removing the prefix, I tested with both a relative module as well as one in the `$env.NU_LIB_DIRS` path, and in all cases the *internal* `std` still took precedence. * By removing the prefix, users can now `use std` (and variants) without requiring that it already be parsed and in scope. * In the next release, we'll stop autoloading the `dirs` (shells) functionality. While this only costs an additional 1-1.5ms, I think it's better moved to the `config.nu` where the user can optionally remove it. The main reason is its use of aliases (which have also caused issues) - The `n`, `p`, and `g` short-commands are valuable real-estate, and users may want to map these to something else. For this release, there's an `deprecated_dirs` module that is still autoloaded. As with the top-level commands, use of these will give a deprecation warning with instructions on how to handle going forward. To help with this, moved the aliases to their own submodule inside the `dirs` module. * Also sneaks in a small change where the top-level `dirs` command is now the replacement for `dirs show` * Fixed a double-import of `assert` in `dirs.nu` * The `show_banner` step is replaced with simply `banner` rather than re-importing it. * A `virtual_path` may now be referenced with either a forward-slash or a backward-slash on Windows. This allows `use std/<submodule>` to work on all platforms. # Performance side-notes: * Future parsing and/or IR improvements should improve performance even further. * While the existing load time penalty of `std-lib` was not noticeable on many systems, Nushell runs on a wide-variety of hardware and OS platforms. Slower platforms will naturally see a bigger jump in performance here. For users starting multiple Nushell sessions frequently (e.g., `tmux`, Zellij, `screen`, et. al.) it is recommended to keep total startup time (including user configuration) under ~250ms. # Tests + Formatting * All tests are green * Updated tests: - Removed the test that confirmed that `std` was loaded (since we don't). - Removed the `shells` test since it is not autoloaded. Main `dirs.nu` functionality is tested through `stdlib-test`. - Many tests assumed that the library was fully loaded, because it was (even though we didn't intend for it to be). Fixed those tests. - Tests now import only the necessary submodules (e.g., `use std/assert`, rather than `use std assert`) - Some tests *thought* they were loading `std/log`, but were doing so improperly. This was masked by the now-fixed "load-everything-into-scope bug". Local CI would pass due the `$env.NU_LOG_<...>` variables being inherited from the calling process, but would fail in the "clean" GitHub CI environment. These tests have also been fixed. * Added additional tests for the changes # After Submitting Will update the Standard Library doc page
2024-10-03 11:28:22 +00:00
# Top-level commands: ellie, repeat, null-device, and "path add"
export use lib *
# std submodules
export module assert
export module bench
export module dt
export module formats
export module help
export module input
export module iter
export module log
export module math
export module xml
# Load main dirs command and all subcommands
export use dirs main
export module dirs {
export use dirs [
add
drop
next
prev
goto
]
}