[1.0.x] SDC Property Inheritance

Thank you for applying!

Before giving links helpful to understand how the review process works, what to expect from a review, and what to do to avoid a review takes more time than needed, I would like to thank all the reviewers for the work they do.
These applications are volunters-driven, which also means it is not possible to predict when an application will be marked fixed and the applicant will get the permission to opt projects into security advisory policy. While we aim to make an application as quick as possible, it is also important for us that more people review the project used for an application. In this way, we make sure applications do not miss some important points that should be instead reported.
Applications are not meant to be complete debugging sessions that eliminate every existing bug, though. I apologize if sometimes applications seem to go into too-detailed reviews.

Please read Review process for security advisory coverage: What to expect for more details and Security advisory coverage application checklist to understand what reviewers look for. Tips for ensuring a smooth review gives some hints for a smoother review.

The important notes are the following.

• If you have not done it yet, you should enable GitLab CI for the project and fix the PHP_CodeSniffer errors/warnings it reports.
• For the time this application is open, only your commits are allowed.
• The purpose of this application is giving you a new drupal.org role that allows you to opt projects into security advisory coverage, either projects you already created, or projects you will create. The project status will not be changed by this application; once this application is closed, you will be able to change the project status from Not covered to Opt into security advisory coverage. This is possible only 14 days after the project is created.
  
  Keep in mind that once the project is opted into security advisory coverage, only Security Team members may change coverage.
• Only the person who created the application will get the permission to opt projects into security advisory coverage. No other person will get the same permission from the same application; that applies also to co-maintainers/maintainers of the project used for the application.
• We only accept an application per user. If you change your mind about the project to use for this application, or it is necessary to use a different project for the application, please update the issue summary with the link to the correct project and the issue title with the project name and the branch to review.

To the reviewers

Please read How to review security advisory coverage applications, Application workflow, What to cover in an application review, and Tools to use for reviews.

The important notes are the following.

• It is preferable to wait for a project moderator before posting the first comment on newly created applications. Project moderators will do some preliminary checks that are necessary before any change on the project files is suggested.
• Reviewers should show the output of a CLI tool only once per application.
• It may be best to have the applicant fix things before further review.

For new reviewers, I would also suggest to first read In which way the issue queue for coverage applications is different from other project queues.

Remember to change status, when the project is ready to be reviewed. In this queue, projects are only reviewed when the status is Needs review.

Reviewed 1.0.x at commit 4d9fc2f. Small, focused module, and a real problem worth solving. Both automated checks are clean: PHPCS (Drupal, DrupalPractice) across 10 files gives 0 errors and 0 warnings, and PHPStan at level 5 reports nothing.

Findings

1. Chained replacement is order dependent

In InheritedComponentPluginManager::alterDefinitions():

foreach ($definitions as $id => $definition) { $definitions[$id] = $this->inheritProps($definition, $definitions); }

The loop iterates a snapshot, but the second argument passes the live array, which is being rewritten as the loop runs. So when inheritProps() looks up $definitions[$parent_id]['props'], it may see the parent either before or after that parent has itself inherited, depending purely on discovery order.

For a single level of replacement this never shows. For a chain, where A replaces B and B in turn replaces C, whether A ends up with C's props depends on whether B happened to be processed first. Discovery order is not something an author controls, and because definitions are cached the outcome gets baked in, so two environments can legitimately disagree.

Worth deciding what chained replacement should mean, then making it deterministic. Resolving parents recursively with a memo, or simply looking parents up in an untouched copy of the original array, both give a stable answer. A test with a three component chain would pin whichever you choose.

2. The "required" merge semantics deserve a line in the README

$definition['props'] += $parent_props; fills in top level keywords the override omits, which includes required. That produces two behaviours that are defensible but not obvious:

• An override that declares properties but no required silently inherits the parent's entire required list.
• An override that declares its own required replaces the parent's outright rather than merging, so it can drop a prop the parent required.

Core's compatibility check will reject the genuinely broken cases, so this is not a correctness problem. It is a documentation one, and the README is the natural place for it since the whole point of the module is that authors stop thinking about the parent schema.

3. Test coverage gap

The four kernel tests cover the manager swap, the no props case, the partial case and the untouched case, which is a good spread for a module this size. The test module has two replacement components and neither is itself replaced, so the chain case in finding 1 is untested. That is the case I would add first.

4. Small accuracy point in the docblock

The class docblock says the merge runs first so that "core still performs its own definition validation, replacement compatibility check and sorting". The compatibility check and the sorting do both run unconditionally, so the substance is right. Definition validation is the exception: core wraps isValidDefinition() in an assert(), so it runs in development and CI but not in production. Worth rewording slightly, because the current phrasing implies more of a runtime safety net than production actually has.

Things I checked and found correct

• The service provider is the right shape. It swaps only the class with setClass() and leaves core owning the arguments, so a constructor change in ComponentPluginManager will not break the module. It also guards with hasDefinition(). This is the detail most modules of this kind get wrong, and the docblock explains why it was done that way.
• The merge is correctly ordered relative to core. The module merges before calling parent::alterDefinitions(), and core's replacement compatibility check runs at the end of that parent call against the merged result, so an override cannot use this module to smuggle through an incompatible schema. Confirmed in ComponentPluginManager::alterDefinitions().
• += is the correct operator here. Union keeps the override's own declarations and only fills gaps, which is exactly what the docblock claims.
• The _inherited debug key is safe. I half expected this to fail validation, but the SDC metadata schema does not set additionalProperties: false at the root, so an extra top level key is permitted.
• CI. OPT_IN_TEST_PREVIOUS_MAJOR with _AUTORUN_PREVIOUS_MAJOR set, so the declared ^10.6 support is actually exercised rather than merely claimed. Nice to see, and the comment explaining why both variables are needed is a kindness to the next maintainer.

Summary

Clean, well scoped and unusually well commented for its size, and the extension point it uses is the upgrade safe one. Finding 1 is the only thing I would want resolved before coverage, and it is a small change plus a test. Findings 2 to 4 are documentation and polish.

I use Assisted AI but I review what it generates