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firefox/docs/code-quality/lint/linters/eslint-plugin-mozilla/rules/reject-import-system-module-from-non-system.rst
Daniel Baumann 5e9a113729
Adding upstream version 140.0.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
2025-06-25 09:37:52 +02:00

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reject-import-system-module-from-non-system
===========================================
Rejects static import declaration for system modules (``.sys.mjs``) from non-system
modules.
Using static import for a system module into a non-system module would create a separate instance of the imported object(s) that is not shared with the other system modules and would break the per-process singleton expectation.
The reason for this is that inside system modules, a static import will load the module into the shared global. Inside non-system modules, the static import will load into a different global (e.g. window). This will cause the module to be loaded into different scopes, and hence create separate instances. The fix is to use ``ChromeUtils.importESModule`` which will import the object via the system module shared global scope.
Examples of incorrect code for this rule:
-----------------------------------------
Inside a non-system module:
.. code-block:: js
import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
Examples of correct code for this rule:
---------------------------------------
Inside a non-system module:
.. code-block:: js
const { AppConstants } = ChromeUtils.importESModule(
"resource://gre/modules/AppConstants.sys.mjs"
);
Inside a system module:
.. code-block:: js
import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";