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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
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# Tests + Formatting
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# After Submitting
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* 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>
* Allow private imports inside modules
Can call `use ...` inside modules now.
* Add more tests
* Add a leak test
* Refactor exportables; Prepare for 'export use'
* Fix description
* Implement 'export use' command
This allows re-exporting module's commands and aliases from another
module.
* Add more tests; Fix import pattern list strings
The import pattern strings didn't trim the surrounding quotes.
* Add ignored test
* Add 'expor env' dummy command
* (WIP) Abstract away module exportables as Overlay
* Switch to Overlays for use/hide
Works for decls only right now.
* Fix passing import patterns of hide to eval
* Simplify use/hide of decls
* Add ImportPattern as Expr; Add use env eval
Still no parsing of "export env" so I can't test it yet.
* Refactor export parsing; Add InternalError
* Add env var export and activation; Misc changes
Now it is possible to `use` env var that was exported from a module.
This commit also adds some new errors and other small changes.
* Add env var hiding
* Fix eval not recognizing hidden decls
Without this change, calling `hide foo`, the evaluator does not know
whether a custom command named "foo" was hidden during parsing,
therefore, it is not possible to reliably throw an error about the "foo"
name not found.
* Add use/hide/export env var tests; Cleanup; Notes
* Ignore hide env related tests for now
* Fix main branch merge mess
* Fixed multi-word export def
* Fix hiding tests on Windows
* Remove env var hiding for now
