Allow caching outputless plugin operations without rush-project.json

[Ian Clanton-Thuon (iclanton)]

Summary

• allow a plugin-defined operation to use the build cache without project configuration when it explicitly declares outputFolderNames: []
• keep project configuration required when the operation declares outputs or cache inputs such as environment variables, Node.js version, or additional files
• apply the same eligibility rule to cache execution and cobuild build-plan analysis
• retain hotlink and explicit cache-disable protections

Validation

• rushx build
• rushx test --test-path-pattern CacheableOperationPlugin.test (37 passed)
• rushx test --test-path-pattern RushProjectConfiguration.test (30 passed)
• rushx test --test-path-pattern BuildPlanPlugin.test (1 passed)
• rush change --verify --no-fetch

Broader test note

A full local rush-lib run was attempted. The changed suites passed, while unrelated environment-sensitive tests failed because daemon tests reject the existing user/repository .env configuration and a tar signal test returned the platform tar exit code 0 instead of 1.

[Copilot]

🟢 Approval recommended

The focused eligibility change preserves the required safeguards, includes regression coverage, and has no identified blocking issues.

0 open findings

What changed in this PR

Allows explicitly outputless plugin operations to use Rush’s build cache without rush-project.json, while preserving cache-input, hotlink, and explicit-disable safeguards.

Changes:

• Shares cache eligibility logic between execution and cobuild planning.
• Adds regression tests for eligible operations and required configuration.
• Updates the public API report and change record.

File	Description
libraries/​rush-lib/​src/​logic/​operations/​test/​CacheableOperationPlugin.test.ts	Tests caching without project configuration.
libraries/​rush-lib/​src/​logic/​operations/​CacheableOperationPlugin.ts	Uses shared eligibility logic.
libraries/​rush-lib/​src/​logic/​operations/​BuildPlanPlugin.ts	Supplies operation settings for planning.
libraries/​rush-lib/​src/​api/​test/​RushProjectConfiguration.test.ts	Tests eligibility restrictions and explicit disabling.
libraries/​rush-lib/​src/​api/​RushProjectConfiguration.ts	Implements and documents outputless-operation eligibility.
common/​reviews/​api/​rush-lib.api.md	Records optional eligibility parameters.
common/​changes/​@microsoft/​rush/​fix-cache-outputless-plugin-operations_2026-10-15-21-41-39.json	Records the caching behavior change.

🧠 Review effort: Balanced

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.