[grid] Support Grid custom capability mutators

[Purus]

User description

Custom capability mutators(with ordering priority) can be placed as part of Grid setup and will be used.

Fixes #13628

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Description

Custom capability mutators(with ordering priority) can be placed as part of Grid setup and will be used.

Motivation and Context

Provides option to update the capabilities based on various aspects. Use cases available in #13628.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the contributing document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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Type

Enhancement

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Description

• Introduced a new CapabilitiesMutatorService to support custom capability mutations with ordering priority.
• Defined a CapabilityMutator interface for implementing custom mutators.
• Updated DriverServiceSessionFactory to use CapabilitiesMutatorService for mutating session capabilities.
• Adjusted SessionCapabilitiesMutator to implement the new CapabilityMutator interface.
• Added comprehensive tests for the new CapabilitiesMutatorService.
• Updated Bazel build configuration to include necessary dependencies.

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Changes walkthrough

	Relevant files
Enhancement	CapabilitiesMutatorService.java Introduce Capabilities Mutator Service for Custom Capability Mutations java/src/org/openqa/selenium/grid/node/config/CapabilitiesMutatorService.java Introduced a new service for mutating capabilities with custom mutators. Custom mutators are loaded using ServiceLoader and sorted by order. Provides a method to mutate capabilities based on the loaded custom mutators. +64/-0    CapabilityMutator.java Define Capability Mutator Interface                                            java/src/org/openqa/selenium/grid/node/config/CapabilityMutator.java Defined an interface for capability mutators with a default order. +29/-0    DriverServiceSessionFactory.java Use CapabilitiesMutatorService in DriverServiceSessionFactory java/src/org/openqa/selenium/grid/node/config/DriverServiceSessionFactory.java Replaced SessionCapabilitiesMutator with CapabilitiesMutatorService for mutating session capabilities. Adjusted imports and cleaned up the code. +21/-40  SessionCapabilitiesMutator.java Update SessionCapabilitiesMutator to Implement CapabilityMutator java/src/org/openqa/selenium/grid/node/config/SessionCapabilitiesMutator.java Made SessionCapabilitiesMutator implement the new CapabilityMutator interface. +3/-7
Tests	CapabilitiesMutatorServiceTest.java Add Tests for CapabilitiesMutatorService                                  java/test/org/openqa/selenium/grid/node/config/CapabilitiesMutatorServiceTest.java Added tests for CapabilitiesMutatorService. Tests cover default mutation, custom mutator application, and custom mutator order. +112/-0
Configuration changes	BUILD.bazel Add Core Dependency to Distributor Config BUILD                    java/src/org/openqa/selenium/grid/distributor/config/BUILD.bazel Added dependency on //java/src/org/openqa/selenium:core for the distributor config. +1/-0

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PR Description updated to latest commit (124a3cc)

• Copy walkthrough table to "Files Changed" Tab

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PR Review

⏱️ Estimated effort to review [1-5]	3, because the PR introduces a new feature with a moderate amount of new code across several files, including core functionality changes, interface definitions, and tests. The logic seems straightforward, but understanding the impact on the existing system and ensuring compatibility requires a thorough review.
🧪 Relevant tests	Yes
🔍 Possible issues	Thread Safety: The CapabilitiesMutatorService class uses a List<CapabilityMutator> for custom mutators which might be accessed by multiple threads. Ensure that access to this list is thread-safe.
	Error Handling: There is no visible error handling or logging in the CapabilitiesMutatorService when applying mutators. Consider adding error handling to catch and log potential issues during the mutation process.
	Dependency Injection: The use of ServiceLoader in CapabilitiesMutatorService to load CapabilityMutator implementations is a static method of discovery. This approach might limit the flexibility in configuring mutators dynamically at runtime. Consider if dependency injection could offer better configurability.
🔒 Security concerns	No

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PR Code Suggestions

Category	Suggestions
Enhancement	Use a thread-safe collection for customMutators. Consider using a thread-safe collection for customMutators since it might be accessed or modified by multiple threads simultaneously. You can use CopyOnWriteArrayList from the java.util.concurrent package to ensure thread safety. java/src/org/openqa/selenium/grid/node/config/CapabilitiesMutatorService.java [31] -private List<CapabilityMutator> customMutators; +private List<CapabilityMutator> customMutators = new CopyOnWriteArrayList<>();
Performance	Cache the comparator used for sorting custom mutators. To improve the efficiency of sorting custom mutators, consider caching the result of Comparator.comparingInt(CapabilityMutator::getOrder).reversed() as a static final field. This avoids creating a new Comparator instance each time the constructor is called. java/src/org/openqa/selenium/grid/node/config/CapabilitiesMutatorService.java [39] -.sorted(Comparator.comparingInt(CapabilityMutator::getOrder).reversed()) +private static final Comparator<CapabilityMutator> MUTATOR_COMPARATOR = Comparator.comparingInt(CapabilityMutator::getOrder).reversed(); +... +.sorted(MUTATOR_COMPARATOR)
Maintainability	Allow CapabilitiesMutatorService to be passed as a parameter. Instead of directly creating a new CapabilitiesMutatorService instance in the constructor, consider allowing it to be passed as a parameter. This would make your class more flexible and easier to test, as you could pass mock or stub implementations of CapabilitiesMutatorService. java/src/org/openqa/selenium/grid/node/config/DriverServiceSessionFactory.java [78] -this.capabilitiesMutatorService = new CapabilitiesMutatorService(this.stereotype); +public DriverServiceSessionFactory( + Tracer tracer, + Predicate<Capabilities> predicate, + DriverService.Builder<?, ?> builder, + Capabilities stereotype, + CapabilitiesMutatorService capabilitiesMutatorService) { + ... + this.capabilitiesMutatorService = capabilitiesMutatorService; +}
	Extract custom mutators loading logic into a separate method. To enhance the readability and maintainability of your code, consider extracting the logic for loading and sorting custom mutators into a separate method. This keeps the constructor clean and makes the code easier to understand. java/src/org/openqa/selenium/grid/node/config/CapabilitiesMutatorService.java [36-40] -ServiceLoader<CapabilityMutator> loader = ServiceLoader.load(CapabilityMutator.class); -customMutators = StreamSupport.stream(loader.spliterator(), false) - .sorted(Comparator.comparingInt(CapabilityMutator::getOrder).reversed()) - .collect(Collectors.toList()); +private void loadCustomMutators() { + ServiceLoader<CapabilityMutator> loader = ServiceLoader.load(CapabilityMutator.class); + customMutators = StreamSupport.stream(loader.spliterator(), false) + .sorted(Comparator.comparingInt(CapabilityMutator::getOrder).reversed()) + .collect(Collectors.toList()); +} +... +loadCustomMutators();
Best practice	Validate input parameters of public methods. It's a good practice to validate the input parameters of public methods to avoid unexpected behavior or errors. Consider adding null checks for the Capabilities parameter in the getMutatedCapabilities method. java/src/org/openqa/selenium/grid/node/config/CapabilitiesMutatorService.java [43] public Capabilities getMutatedCapabilities(Capabilities desiredCapabilities) { + Objects.requireNonNull(desiredCapabilities, "desiredCapabilities must not be null"); + ... +}

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[krmahadevan]

I think the customMutators is expected to be populated as soon as the object gets created. After that Its only going to be iterated upon. So do we still need a CopyOnWriteArrayList? Can we not just use ArrayList instead ?

[krmahadevan]

It would be good if you could create a common method that internally takes care of building a stream, sorting the collection and returning back the list. This common method should be called via the loadAllCustomMutators and setCustomMutators. That way, the sorting part is also tested out.

[krmahadevan]

Can we please revert back this wildcard import?

[krmahadevan]

Selenium is using Require.nonNull. So for consistency sake, maybe we can use that instead of Objects.requireNonNull

[krmahadevan]

The defaultMutator seems to be based off of stereoType which is the same throughout the lifecycle of this object. So does it need to be created multiple times?

[krmahadevan]

Please help revert the wild card imports.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.48%. Comparing base (7384157) to head (78bd7b2).

❗ Current head 78bd7b2 differs from pull request most recent head c6ea843. Consider uploading reports for the commit c6ea843 to get more accurate results

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Additional details and impacted files

@@           Coverage Diff           @@
##            trunk   #13672   +/-   ##
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  Coverage   58.48%   58.48%           
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  Files          86       86           
  Lines        5270     5270           
  Branches      220      220           
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  Hits         3082     3082           
  Misses       1968     1968           
  Partials      220      220           

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[diemol]

Thank you for starting this work, @Purus.

I need help to grasp the general idea of the implementation. Why do we need a service for this? I do not understand the need to have several capability mutators. This implementation seems too complex for the requirement. I believe the idea is to overwrite the default capabilities mutator.

Why not follow the concept we have with other pieces? For example, SlotMatcher and DefaultSlotMatcher?