build: nx build caching, dependency-cruiser deps lint, ts emits

[mikehardy]

Summary

• Nx local prepare cache — yarn lerna:prepare runs through the Lerna/Nx runner with scoped inputs, declared outputs, and CI .nx/cache (no Nx Cloud); devDependency graph enforces build order across 17 packages.
• dependency-cruiser lint:deps — cycles, relative-dist imports, and hub/satellite import boundaries are linted in CI via yarn lint.
• TypeScript declaration maps — package builds emit declarationMap for IDE go-to-definition into lib/ sources.
• Jest AI mock gating — global setup skips network fetches on non-AI test runs; Jest 30 --testPathPatterns handled.
• Benchmark script — scripts/benchmark-prepare.sh captures cold install, full rebuild, no-op, and single-package edit scenarios.

Prepare benchmark (macOS, scripts/benchmark-prepare.sh)

Scenario	Name	Pre-Nx median (s)	Post-Nx median (s)	Speedup
A	Cold install	125.6	95.1	~1.3×
B	Full rebuild	23.7	1.9	~12.6×
C	No-op rebuild	23.7	1.4	~16.8×
D	Single-package edit	23.8	1.5*	~16.3×

*Scenario D first run is a cache miss (~5.3s); median uses warm cache hits on iterations 2–3.

Test plan

• yarn lerna:prepare deterministic (Nx cache hits on repeat)
• yarn lint (incl. lint:deps), yarn tsc:compile, yarn compare:types, yarn tests:jest
• Full-tier e2e: macOS 710/0/34, iOS 848/0/85, Android 878/0/54

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces significant improvements to the monorepo build infrastructure by integrating Nx for local computation caching and formalizing the package dependency graph. These changes, combined with new dependency-cycle linting and TypeScript declaration maps, enhance build reliability, developer productivity, and IDE support. The PR also includes comprehensive documentation for these new tooling decisions and a benchmark script to validate the performance gains.

Highlights

• Nx Build Caching: Implemented local Nx computation caching via nx.json to significantly accelerate rebuilds and prepare tasks, with neverConnectToCloud enabled for local-only operation.
• Dependency Linting: Introduced dependency-cruiser as yarn lint:deps to enforce architectural boundaries, prevent circular dependencies, and restrict cross-package imports.
• TypeScript Improvements: Enabled declarationMap in package builds to support IDE go-to-definition functionality directly into the source code.
• Build Graph Optimization: Encoded the build graph using devDependencies to ensure deterministic, correctly-ordered package builds across the monorepo.
• Test Infrastructure: Gated AI mock network fetches to run only during AI-specific test runs, improving determinism and cacheability of the prepare task.

Ignored Files

• Ignored by pattern: .github/workflows/** (5)
  • .github/workflows/linting.yml
  • .github/workflows/tests_e2e_android.yml
  • .github/workflows/tests_e2e_ios.yml
  • .github/workflows/tests_e2e_other.yml
  • .github/workflows/tests_jest.yml

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[gemini-code-assist]

Code Review

This pull request introduces monorepo tooling enhancements for React Native Firebase, including the integration of Nx local caching, deterministic build ordering via devDependencies, dependency-cycle linting with dependency-cruiser, and TypeScript declaration maps. Additionally, AI test mock fetching is moved to a gated Jest global setup to ensure build determinism, and a benchmark script is added. The review feedback is highly constructive and should be fully addressed: it suggests replacing the glob in the dependency linter to support Windows, hardening the Jest global setup argument parsing to prevent redundant mock fetches, replacing deprecated perl invocations with Node.js in the benchmark script, and using standard array indexing instead of .at(0) for backward compatibility.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.64%. Comparing base (1bad118) to head (68d318a).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #9100      +/-   ##
============================================
- Coverage     58.66%   58.64%   -0.02%     
+ Complexity     1617     1616       -1     
============================================
  Files           503      503              
  Lines         39180    39180              
  Branches       5807     5743      -64     
============================================
- Hits          22981    22973       -8     
+ Misses        14800    14743      -57     
- Partials       1399     1464      +65     

Flag	Coverage Δ
android-native	53.56% <ø> (-<0.01%)	⬇️
e2e-ts-android	49.98% <ø> (-0.02%)	⬇️
e2e-ts-ios	53.94% <ø> (-0.01%)	⬇️
e2e-ts-macos	41.49% <ø> (ø)
ios-native	53.94% <ø> (-0.01%)	⬇️
jest	49.58% <ø> (ø)

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