Characterize plugin registry load order and lookup contract

[jamesfredley]

Summary

• add a test-only characterization spec that pins the public plugin-registry contract a future load/registry optimization must preserve
• asserts the two DISTINCT public observables separately: the actual load sequence consumed by loadPlugins() / getPluginsInLoadOrder() and the getAllPlugins() topological order
• covers repeated-build determinism, duplicate-registration dedup, and name/class-name/version lookup identity (each resolves the same non-null tail instance)

Scope note

Test-only; no production changes. Exercises only public GrailsPluginManager APIs and deliberately does not duplicate the existing GrailsPluginSorterSpec sorter coverage - it characterizes end-to-end manager registry output instead.

Verification

• :grails-core:test --tests DefaultGrailsPluginManagerRegistryContractSpec
• :grails-core:test
• git diff --check

This is an AI-generated starting point pinning the plugin-registry/load-order contract.

[Copilot]

Pull request overview

Adds a new characterization-style Spock spec to pin down the publicly observable GrailsPluginManager registry behavior around plugin load order vs topological order, including determinism across repeated builds, deduplication, and consistent lookup identity across name/class-name/version APIs. This helps protect expected behavior ahead of future plugin discovery/registry optimizations.

Changes:

• Introduces DefaultGrailsPluginManagerRegistryContractSpec to assert deterministic plugin discovery load order and deterministic topological registry order for the same dependency graph.
• Adds coverage for duplicate-registration deduplication and consistent lookup resolution (getGrailsPlugin, getGrailsPluginForClassName, versioned lookup) returning the same instance.

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[bito-code-review]

To make the selection safe and avoid NoSuchElementException when the list is empty, you can use .find() or .first() with a default value, or check the size before accessing. Given the context of the test, using find { true } or checking the list size is appropriate to ensure the then: block handles the failure reporting correctly.

Here is the suggested update for the test:

        when:
        def tailPlugins = manager.getAllPlugins().findAll { it.name == 'registryOrderingTail' }
        def expectedTailPlugin = tailPlugins ? tailPlugins.first() : null
        def pluginByName = manager.getGrailsPlugin('registryOrderingTail')

This change ensures that expectedTailPlugin is null if the list is empty, allowing the subsequent assertions in the then: block to fail gracefully with descriptive messages rather than throwing an exception.

grails-core/src/test/groovy/grails/plugins/DefaultGrailsPluginManagerRegistryContractSpec.groovy

when:
        def tailPlugins = manager.getAllPlugins().findAll { it.name == 'registryOrderingTail' }
        def expectedTailPlugin = tailPlugins ? tailPlugins.first() : null
        def pluginByName = manager.getGrailsPlugin('registryOrderingTail')

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.4649%. Comparing base (0c63c26) to head (0b53a85).
⚠️ Report is 128 commits behind head on 8.0.x.

Additional details and impacted files

@@                Coverage Diff                 @@
##                8.0.x     #16004        +/-   ##
==================================================
+ Coverage     51.1168%   51.4649%   +0.3480%     
- Complexity      17597      17753       +156     
==================================================
  Files            2041       2039         -2     
  Lines           95493      95537        +44     
  Branches        16587      16571        -16     
==================================================
+ Hits            48813      49168       +355     
+ Misses          39394      39065       -329     
- Partials         7286       7304        +18     

see 109 files with indirect coverage changes

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