mirror of
https://github.com/nushell/nushell.git
synced 2025-05-03 01:24:29 +02:00
# Description While working on something else, I noticed that `Value::follow_cell_path` receives `self`. While it would be ideal for the signature to be `(&'a self, cell_path) -> &'a Value`, that's not possible because: 1. Selecting a row from a list and field from a record can be done with a reference but selecting a column from a table requires creating a new list. 2. `Value::Custom` returns new `Value`s when indexed. So the signature becomes `(&'a self, cell_path) -> Cow<'a, Value>`. Another complication that arises is, once a new `Value` is created, and it is further indexed, the `current` variable 1. can't be `&'a Value`, as the lifetime requirement means it can't refer to local variables 2. _shouldn't_ be `Cow<'a, Value>`, as once it becomes an owned value, it can't be borrowed ever again, as `current` is derived from its previous value in further iterations. So once it's owned, it can't be indexed by reference, leading to more clones We need `current` to have _two_ possible lifetimes 1. `'out`: references derived from `&self` 2. `'local`: references derived from an owned value stored in a local variable ```rust enum MultiLife<'out, 'local, T> where 'out: 'local, T: ?Sized, { Out(&'out T), Local(&'local T), } ``` With `current: MultiLife<'out, '_, Value>`, we can traverse values with minimal clones, and we can transform it to `Cow<'out, Value>` easily (`MultiLife::Out -> Cow::Borrowed, MultiLife::Local -> Cow::Owned`) to return it # User-Facing Changes # Tests + Formatting # After Submitting --------- Co-authored-by: Bahex <17417311+Bahex@users.noreply.github.com> |
||
---|---|---|
.. | ||
src | ||
tests | ||
Cargo.toml | ||
LICENSE | ||
README.md |
This crate implements the core functionality of the interactive Nushell REPL and interfaces with reedline
.
Currently implements the syntax highlighting and completions logic.
Furthermore includes a few commands that are specific to reedline
Internal Nushell crate
This crate implements components of Nushell and is not designed to support plugin authors or other users directly.