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doc/module-system: Apply suggestions from code review

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Co-authored-by: Valentin Gagarin <valentin@gagarin.work>
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Robert Hensing
2025-05-09 18:26:10 +02:00
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doc/module-system/module-system.chapter.md
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@@ -127,7 +127,7 @@ They originate from these sources:
- `options`,
- `_class`,
- `_prefix`,
2. Attributes from the [`specialArgs`] which were passed to [`evalModules`] or `submoduleWith`. These are application-specific.
2. Attributes from the [`specialArgs`] argument passed to [`evalModules`] or `submoduleWith`. These are application-specific.
3. Attributes from the `_module.args` option value. These are application-specific and can be provided by any module.
The prior two categories are available while evaluating the `imports`, whereas
@@ -152,11 +152,13 @@ The [expected class](#module-system-lib-evalModules-param-class) of the loaded m
### `_prefix` {#module-system-module-argument-_prefix}
The location under which the module is evaluated. This is used to improve error reporting and find the implicit `name` module argument in submodules.
The location under which the module is evaluated.
This is used to improve error reporting and to find the implicit `name` module argument in submodules.
It is exposed as a module argument due to how the module system is implemented, which cannot be avoided without breaking compatibility.
It is a good practice not to rely on `_prefix`. A module should not make assumptions about its location in the configuration tree.
For example, the root of a NixOS configuration may have a non-empty prefix, for example when it is a specialisation, or when it is part of a larger, multi-host configuration such as a [NixOS test](https://nixos.org/manual/nixos/unstable/#sec-nixos-tests).
Any dependencies on `_prefix` should be replaced with explicit options, whose default definitions can be provided by the module that imports them.
Instead of depending on `_prefix` use explicit options, whose default definitions can be provided by the module that imports them.
[`evalModules`]: #module-system-lib-evalModules
[`specialArgs`]: #module-system-lib-evalModules-param-specialArgs