Allow setup:upgrade and setup:db-data:upgrade to run with a read-only app/etc (#26292)

[lbajsarowicz]

Description (*)

setup:upgrade --keep-generated and setup:db-data:upgrade cannot run when app/etc is read-only, which is the expected state for immutable deployments (prebuilt container images, Kubernetes, chmod 444 app/etc/*). Two independent causes, one commit each:

1. Installer::updateModulesSequence() always rewrites app/etc/config.php.
   createModulesConfig() recomputes the modules array and calls Writer::saveConfig() unconditionally, even when the result is byte-for-byte what is already deployed. On a read-only config.php this fails with The "config.php" deployment config file isn't writable.
   Fix: only call saveConfig() when the computed module list differs (!==, so a changed module sequence still triggers a write) from the current modules section.

2. FilePermissions::getMissingWritableDirectoriesForDbUpgrade() requires app/etc to be writable.
   Installer::installDataFixtures() runs this precondition, so setup:db-data:upgrade (and the data phase of setup:upgrade) aborts with Missing write permissions to the following paths: <root>/app/etc before touching the database. The DB upgrade itself writes only to the database and var/.
   Fix: drop DirectoryList::CONFIG from the list; var/ is still required. A patch that genuinely needs to write deployment configuration (e.g. Magento\Backend\Setup\Patch\Data\MigrateRedisBackendConfig) still gets a precise error from DeploymentConfig\Writer at the moment of the write instead of a blanket refusal up front.

No public signatures changed.

Related Pull Requests

• Separate cache_types from app/etc/config.php #32605 addresses the cache_types / env.php side of Read-only app/etc/ #26292 and is on hold; this PR is independent of it.

Fixed Issues (if relevant)

1. Fixes Read-only app/etc/ #26292

Manual testing scenarios (*)

1. Install Magento 2.4-develop, run bin/magento setup:upgrade once so config.php is in sync.
2. chmod 555 app/etc && chmod 444 app/etc/*
3. bin/magento setup:upgrade --keep-generated
   • before: Upgrade failed: The "config.php" deployment config file isn't writable.
   • after: Upgrade completed successfully.
4. bin/magento setup:db-data:upgrade
   • before: Missing write permissions to the following paths: /var/www/html/app/etc
   • after: completes, exit code 0.
5. Restore permissions, enable/disable a module (bin/magento module:disable Magento_Wishlist), run bin/magento setup:upgrade --keep-generated — config.php is rewritten as before.

Questions or comments

Unit tests: setup/src/Magento/Setup/Test/Unit/Model/InstallerTest.php (write skipped when unchanged, write performed when module order changes) and lib/internal/Magento/Framework/Setup/Test/Unit/FilePermissionsTest.php (read-only app/etc not reported). Both new tests fail against 2.4-develop without the fix.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined templates (if applicable)
• All automated tests passed successfully (all builds are green)

[lbajsarowicz]

@magento run all tests

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[lbajsarowicz]

@magento run all tests

[lbajsarowicz]

@magento run all tests

[lbajsarowicz]

@magento run all tests

[lbajsarowicz]

@magento run Unit Tests, WebAPI Tests