NoOpImplementation improvements [3/3] RUM-16477 Add NoOp name collision detection and customName support

[satween]

What does this PR do?

Adds collision detection to the NoOp KSP processor and a new customName parameter to @NoOpImplementation. When two interfaces would generate the same NoOp* class name (e.g. Outer.Inner and OuterInner both produce NoOpOuterInner), the processor now emits a clear error and suggests using customName to resolve the conflict. The customName parameter lets callers override the generated class name entirely.

Motivation

Without collision detection, two distinct interfaces silently clobber each other's generated file, producing broken or incomplete NoOp implementations at build time with no diagnostic. The new guard catches this at KSP processing time with actionable error messages.

Additional Notes

• Validates customName against a Kotlin identifier regex and reports a clear error for names like "My.Invalid.Name".
• Detects both same-round name collisions (via an in-process generatedNames map) and pre-existing file conflicts (via FileAlreadyExistsException).
• ThrowingCodeGeneratorProvider test helper retained because KSP 1.8.0 does not throw FileAlreadyExistsException for disk files from previous builds; two-pass compilation silently overwrites.
• All 8 new test cases pass; no existing tests regressed.
• generateNoOpImplementation refactored into resolveNoOpClassName, reportNameCollision, and writeNoOpFile helpers to satisfy detekt LongMethod / ReturnCount limits.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

Ref: RUM-7390

[satween]

• NoOpImplementation improvements [3/3] RUM-16477 Add NoOp name collision detection and customName support #3470 👈 (View in Graphite)
• NoOpImplementation improvements [2/3] RUM-16477 Guard NoOp generation against restricted-visibility #3469
• NoOpImplementation improvements [1/3] RUM-16477 Support for nested interfaces #3468
• develop

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.24%. Comparing base (d8f145f) to head (f59462b).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3470      +/-   ##
===========================================
+ Coverage    72.18%   72.24%   +0.06%     
===========================================
  Files          964      964              
  Lines        35583    35583              
  Branches      5926     5926              
===========================================
+ Hits         25684    25705      +21     
+ Misses        8280     8269      -11     
+ Partials      1619     1609      -10     

see 39 files with indirect coverage changes

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[Copilot]

Pull request overview

Adds support for explicit NoOp implementation names and collision diagnostics in the NoOp KSP processor.

Changes:

• Adds customName to @NoOpImplementation.
• Detects generated-name collisions and existing generated-file conflicts with clearer errors.
• Adds processor tests and fixtures for custom names, invalid names, and collision scenarios.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tools/noopfactory/src/main/kotlin/com/datadog/tools/annotation/NoOpImplementation.kt	Extends the annotation API with customName.
tools/noopfactory/src/main/kotlin/com/datadog/tools/noopfactory/NoOpAnnotationExt.kt	Adds helper logic for safe annotation argument reads and name resolution.
tools/noopfactory/src/main/kotlin/com/datadog/tools/noopfactory/NoOpFactorySymbolProcessor.kt	Implements custom name resolution, collision detection, and file-exists error reporting.
tools/noopfactory/src/test/kotlin/com/datadog/tools/noopfactory/NoOpFactoryProviderTest.kt	Adds tests for custom names and collision/error paths.
tools/noopfactory/src/test/resources/src/CollidingInterfaces.kt	Fixture for default generated-name collision.
tools/noopfactory/src/test/resources/src/CustomNameCollidingWithGenerated.kt	Fixture for custom name colliding with an auto-generated name.
tools/noopfactory/src/test/resources/src/CustomNameInterface.kt	Fixture for successful custom name generation.
tools/noopfactory/src/test/resources/src/InvalidCustomNameInterface.kt	Fixture for invalid custom name validation.
tools/noopfactory/src/test/resources/src/PreExistingFileCustomNameInterface.kt	Fixture for existing-file conflict with custom name.
tools/noopfactory/src/test/resources/src/PreExistingFileInterface.kt	Fixture for existing-file conflict with default name.
tools/noopfactory/src/test/resources/src/SameCustomName.kt	Fixture for duplicate custom names.
tools/noopfactory/src/test/resources/gen/MyCustomNoOp.kt	Expected generated output for custom name generation.

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