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# Description
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Relative: #8248
After this pr, user can define const variable inside a module.
And user can export const variables, the following screenshot shows how
it works (it follows
https://github.com/nushell/nushell/issues/8248#issuecomment-1637442612):
## About the change
1. To make module support const, we need to change `parse_module_block`
to support `const` keyword.
2. To suport export `const`, we need to make module tracking variables,
so we add `variables` attribute to `Module`
3. During eval, the const variable may not exists in `stack`, because we
don't eval `const` when we define a module, so we need to find variables
which are already registered in `engine_state`
## One more thing to note about the const value.
Consider the following code
```
module foo { const b = 3; export def bar [] { $b } }
use foo bar
const b = 4;
bar
```
The result will be 3 (which is defined in module) rather than 4. I think
it's expected behavior.
It's something like [dynamic
binding](https://www.gnu.org/software/emacs/manual/html_node/elisp/Dynamic-Binding-Tips.html)
vs [lexical
binding](https://www.gnu.org/software/emacs/manual/html_node/elisp/Lexical-Binding.html)
in lisp like language, and lexical binding should be right behavior
which generates more predicable result, and it doesn't introduce really
subtle bugs in nushell code.
What if user want dynamic-binding?(For example: the example code returns
`4`)
There is no way to do this, user should consider passing the value as
argument to custom command rather than const.
## TODO
- [X] adding tests for the feature.
- [X] support export const out of module to use.
# User-Facing Changes
<!-- List of all changes that impact the user experience here. This
helps us keep track of breaking changes. -->
# Tests + Formatting
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Don't forget to add tests that cover your changes.
Make sure you've run and fixed any issues with these commands:
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fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect -A clippy::result_large_err` to check that
you're using the standard code style
- `cargo test --workspace` to check that all tests pass
- `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
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documentation](https://github.com/nushell/nushell.github.io) after the
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# Description
For years, Nushell has used `let-env` to set a single environment
variable. As our work on scoping continued, we refined what it meant for
a variable to be in scope using `let` but never updated how `let-env`
would work. Instead, `let-env` confusingly created mutations to the
command's copy of `$env`.
So, to help fix the mental model and point people to the right way of
thinking about what changing the environment means, this PR removes
`let-env` to encourage people to think of it as updating the command's
environment variable via mutation.
Before:
```
let-env FOO = "BAR"
```
Now:
```
$env.FOO = "BAR"
```
It's also a good reminder that the environment owned by the command is
in the `$env` variable rather than global like it is in other shells.
# User-Facing Changes
BREAKING CHANGE BREAKING CHANGE
This completely removes `let-env FOO = "BAR"` so that we can focus on
`$env.FOO = "BAR"`.
# 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 -A clippy::result_large_err` to check that
you're using the standard code style
- `cargo test --workspace` to check that all tests pass
- `cargo run -- crates/nu-std/tests/run.nu` 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 / Before Submitting
integration scripts to update:
- ✔️
[starship](https://github.com/starship/starship/blob/master/src/init/starship.nu)
- ✔️
[virtualenv](https://github.com/pypa/virtualenv/blob/main/src/virtualenv/activation/nushell/activate.nu)
- ✔️
[atuin](https://github.com/ellie/atuin/blob/main/atuin/src/shell/atuin.nu)
(PR: https://github.com/ellie/atuin/pull/1080)
- ❌
[zoxide](https://github.com/ajeetdsouza/zoxide/blob/main/templates/nushell.txt)
(PR: https://github.com/ajeetdsouza/zoxide/pull/587)
- ✔️
[oh-my-posh](https://github.com/JanDeDobbeleer/oh-my-posh/blob/main/src/shell/scripts/omp.nu)
(pr: https://github.com/JanDeDobbeleer/oh-my-posh/pull/4011)
# Description
This is an experiment to see what switching the `let/let-env` family to
math expressions for initialisers would be like.
# User-Facing Changes
This would require any commands you call from `let x = <command here>`
(and similar family) to call the command in parentheses. `let x = (foo)`
to call `foo`.
# 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
> **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.
* remove export_env command
* remove several export env usage in test code
* adjust hiding relative test case
* fix clippy
* adjust tests
* update tests
* unignore these tests to expose ut failed
* using `use` instead of `overlay use` in some tests
* Revert "using `use` instead of `overlay use` in some tests"
This reverts commit 2ae24b24c3.
* Revert "adjust hiding relative test case"
This reverts commit 4369af6d05.
* Bring back module example
* Revert "update tests"
This reverts commit 6ae94ef513.
* Fix tests
* "Fix" a test
* Remove remaining deprecated env functionality
* Re-enable environment hiding for `hide`
To not break virtualenv since the overlay update is not merged yet
* Fix hiding env in `hide` and ignore some tests
Co-authored-by: kubouch <kubouch@gmail.com>
