nushell/crates/nu-cmd-lang
Devyn Cairns 2ae9ad8676
Copy-on-write for record values (#12305)
# Description
This adds a `SharedCow` type as a transparent copy-on-write pointer that
clones to unique on mutate.

As an initial test, the `Record` within `Value::Record` is shared.

There are some pretty big wins for performance. I'll post benchmark
results in a comment. The biggest winner is nested access, as that would
have cloned the records for each cell path follow before and it doesn't
have to anymore.

The reusability of the `SharedCow` type is nice and I think it could be
used to clean up the previous work I did with `Arc` in `EngineState`.
It's meant to be a mostly transparent clone-on-write that just clones on
`.to_mut()` or `.into_owned()` if there are actually multiple
references, but avoids cloning if the reference is unique.

# User-Facing Changes
- `Value::Record` field is a different type (plugin authors)

# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting
- [ ] use for `EngineState`
- [ ] use for `Value::List`
2024-04-14 01:42:03 +00:00
..
src Copy-on-write for record values (#12305) 2024-04-14 01:42:03 +00:00
build.rs Cratification: Break out nu_cmd_lang into a separate crate (#8181) 2023-02-24 09:54:42 -06:00
Cargo.toml Bump version to 0.92.3 (#12476) 2024-04-12 08:00:43 -05:00
LICENSE Fix rest of license year ranges (#8727) 2023-04-04 09:03:29 +12:00
README.md nu-cmd-lang readme (#9446) 2023-06-15 08:45:23 -07:00

nu-cmd-lang

the base language and command crate of nu

The commands in this crate are the core commands of the nu language. It is also the base crate upon which all other command crates sit on top of including:

  • nu-command
  • nu-cli
  • nu-cmd-dataframe
  • nu-cmd-extra

As time goes on and the nu language develops further in parallel with nushell we will be adding other command crates to the system.

What does it mean to be a base crate ?

A base crate is one with minimal dependencies in our system so that other developers can come along and use this crate without having a lot of baggage in terms of other crates which will bloat their underlying application.

Background on nu-cmd-lang

This crate was designed to be a small, concise set of tools or commands that serve as the foundation layer of both nu and nushell. These are the core commands needed to have a nice working version of the nu language without all of the support that the other commands provide inside nushell. Prior to the launch of this crate all of our commands were housed in the crate nu-command. Moving forward we would like to slowly break out the commands in nu-command into different crates; the naming and how this will work and where all the commands will be located is a "work in progress" especially now that the standard library is starting to become more popular as a location for commands. As time goes on some of our commands written in rust will be migrated to nu and when this happens they will be moved into the standard library.