Refactor ProjectGraphGenerator to expose read-only graph results

[cdsap]

Problem

ProjectGraphGenerator.generate() returns MutableList at project-generator/src/main/kotlin/io/github/cdsap/projectgenerator/ProjectGraphGenerator.kt:16, although callers only read the generated graph and ProjectGraph itself is immutable.

Why This Matters

The mutable return type leaks construction details across the domain boundary and permits callers to alter generated graph state after creation, increasing coupling and making behavior harder to reason about.

Proposed Change

Change generate() to return List while retaining a private mutable accumulator during construction. Add or update a focused test documenting that the generated graph is consumed as a read-only result.

Files

• project-generator/src/main/kotlin/io/github/cdsap/projectgenerator/ProjectGraphGenerator.kt
• project-generator/src/test/kotlin/io/github/cdsap/projectgenerator/ProjectGraphGeneratorTest.kt

Constraints

• Preserve behavior.
• Preserve graph contents, ordering, and generation behavior.
• Preserve existing Kotlin style and public usage patterns where possible.
• Do not redesign graph generation or introduce new frameworks.
• Keep this as a small refactor; do not perform a broad architecture migration.
• Do not change public APIs unless the issue explicitly requires it.

Acceptance Criteria

• ProjectGraphGenerator exposes List rather than MutableList.
• Existing graph-generation tests continue to pass unchanged or with only type-focused adjustments.
• ./gradlew :project-generator:unitTest passes.
• ./gradlew :cli:test passes.
• ./gradlew ktlintCheck passes.
• Existing behavior is preserved.

Validation

• ./gradlew :project-generator:unitTest
• ./gradlew :cli:test
• ./gradlew ktlintCheck

Notes

This clarifies the domain boundary: graph construction remains internally mutable, while the generated graph is returned as an immutable domain result. Because the library is published, review downstream source compatibility before applying the signature change.