feat(pm): Package manager agnostic install(), add(), dedupe()

[Tobbe]

Add helper methods for getting the package manager specific install, add and dedupe commands

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[greptile-apps]

Greptile Summary

This PR makes the Cedar CLI package-manager-agnostic by introducing a set of helper functions (add(), install(), dedupe(), dedupeIsSupported(), installationErrorMessage(), prettyPrintCedarCommand()) in @cedarjs/cli-helpers/packageManager and updating getPackageManager() in @cedarjs/project-config to detect the active package manager from the npm_config_user_agent environment variable before falling back to lock-file detection. Callers throughout the CLI (installHelpers, setupRscHandler, baremetal, and the upgrade command) are migrated away from hardcoded yarn invocations.

Key changes:

• New PM detection priority: env var (npm_config_user_agent) > lock files > default yarn — the env var tells the CLI which package manager actually invoked the current command.
• upgrade command: --dedupe option is now hidden for non-yarn users; the dedupeDeps task is correctly skipped for npm/pnpm via the dedupeIsSupported() guard.
• dedupe() helper returns undefined for non-yarn PMs: it is used in template literals inside dedupeDeps without an explicit null guard — safe today due to control-flow, but fragile (see inline comment).
• No tests for new cli-helpers/packageManager functions: add(), install(), deduce(), etc. are untested (see inline comment).

Confidence Score: 4/5

• PR is safe to merge; all previously flagged issues are resolved and the remaining comments are non-blocking style suggestions.
• The core logic is sound: the dedupeDeps function is correctly gated so it only runs for yarn, prior critical issues (hardcoded yarn dedupe, afterEach env var coercion) have been addressed, and the env-var-first detection strategy is coherent. The remaining P2 items — no null guard on dedupeCmd() in template literals and missing unit tests for the new helpers — are improvements rather than blockers.
• packages/cli/src/commands/upgrade/upgradeHandler.ts (dedupeCmd null safety), packages/cli-helpers/src/packageManager/tests/index.test.ts (missing tests for new helpers)

Important Files Changed

Filename	Overview
packages/project-config/src/packageManager.ts	Adds env var (npm_config_user_agent) as the highest-priority signal for package manager detection, falling back to lock files. The default is now set eagerly at the top, and an isPackageManager type guard is introduced. The old multi-return structure is collapsed into a clean if/else chain.
packages/cli-helpers/src/packageManager/index.ts	Adds add(), install(), dedupe(), dedupeIsSupported(), installationErrorMessage(), and prettyPrintCedarCommand() helpers. deduce() returns `string
packages/cli/src/commands/upgrade/upgradeHandler.ts	Migrates from hardcoded yarn to PM-agnostic helpers throughout. The dedupeDeps function is correctly gated (only runs on yarn) so dedupeCmd() will never return undefined in practice, but the template literal use of a nullable return is fragile. Error messages and task titles are now PM-aware.
packages/cli-helpers/src/lib/installHelpers.ts	Correctly replaces hardcoded yarn with getPackageManager() and add(). Minor inconsistency: installPackages hardcodes 'install' instead of calling install(), but this is not a functional issue.
packages/project-config/src/tests/packageManager.test.ts	Adds afterEach cleanup and a new test for the env var detection path. The env var restoration correctly handles the undefined case (addressed from a prior review thread).

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[getPackageManager called] --> B{Cache populated?}
    B -- Yes --> C[Return cached value]
    B -- No --> D[Set default: yarn]
    D --> E{npm_config_user_agent\nenv var set?}
    E -- Yes, valid PM --> F[Use env var PM\ne.g. yarn / npm / pnpm]
    E -- No / unrecognised --> G{yarn.lock exists?}
    G -- Yes --> H[Use yarn]
    G -- No --> I{pnpm-lock.yaml exists?}
    I -- Yes --> J[Use pnpm]
    I -- No --> K{package-lock.json exists?}
    K -- Yes --> L[Use npm]
    K -- No --> M[Fallback: yarn]
    F --> N[Cache & return]
    H --> N
    J --> N
    L --> N
    M --> N

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_{Reviews (3): Last reviewed commit: "fix CI and review comments" | Re-trigger Greptile}

[nx-cloud]

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☁️ Nx Cloud last updated this comment at 2026-03-25 11:38:52 UTC

[Tobbe]

@greptileai please do a full review again

[Tobbe]

@greptileai please review once more

[github-actions]

The changes in this PR are now available on npm.

Try them out by running yarn cedar upgrade -t 4.0.0-canary.13674