nushell/crates/nu-parser/src
Jakub Žádník 2388e1e80b
Reorder export-env eval and allow reloading an overlay (#7231)
# Description

This PR is a response to the issues raised in
https://github.com/nushell/nushell/pull/7087. It consists of two
changes:
* `export-env`, when evaluated in `overlay use`, will see the original
environment. Previously, it would see the environment from previous
overlay activation.
* Added a new `--reload` flag that reloads the overlay. Custom
definitions will be kept but the original definitions and environment
will be reloaded.

This enables a pattern when an overlay is supposed to shadow an existing
environment variable, such as `PROMPT_COMMAND`, but `overlay use` would
keep loading the value from the first activation. You can easily test it
by defining a module
```
module prompt {
    export-env {
        let-env PROMPT_COMMAND = (date now | into string)
    }
}
```
Calling `overlay use prompt` for the first time changes the prompt to
the current time, however, subsequent calls of `overlay use` won't
change the time. That's because overlays, once activated, store their
state so they can be hidden and restored at later time. To force-reload
the environment, use the new flag: Calling `overlay use --reload prompt`
repeatedly now updates the prompt with the current time each time.

# User-Facing Changes

* When calling `overlay use`, if the module has an `export-env` block,
the block will see the environment as it is _before_ the overlay is
activated. Previously, it was _after_.
* A new `overlay use --reload` flag.

# 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

# 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.
2022-11-24 23:45:24 +01:00
..
deparse.rs fix arg parse (#5754) 2022-06-11 20:52:31 +12:00
errors.rs Limited mutable variables (#7089) 2022-11-11 19:51:08 +13:00
flatten.rs Make external command substitution works friendly(like fish shell, trailing ending newlines) (#7156) 2022-11-23 16:51:57 +13:00
known_external.rs Change how to identify custom comamnd (#6187) 2022-08-02 18:40:07 -05:00
lex.rs Stdout/Stderr redirection (#7185) 2022-11-23 07:26:13 +13:00
lib.rs Parser refactoring for improving pipelines (#7162) 2022-11-19 10:46:48 +13:00
parse_keywords.rs Reorder export-env eval and allow reloading an overlay (#7231) 2022-11-24 23:45:24 +01:00
parser.rs Remove And and Or pipeline elements (#7229) 2022-11-25 07:06:12 +13:00
type_check.rs Add additional assignment operators (#7102) 2022-11-12 07:50:43 +13:00