perf(start): construct compiler-owned server function AST directly by Sheraff · Pull Request #8524 · TanStack/router

Sheraff · 2026-09-27T18:06:42Z

🎯 Changes

Stacks on #8523; base branch: codex/fuse-clone-provenance.

Server-function compilation currently reparses compiler-owned JavaScript snippets for RPC calls, provider wrappers, imports, directives, and HMR guards. Construct those nodes directly with typed AST builders, preserving generated-reference ownership, source maps, and emitted code.

Compound builders live in named functions with readable inline snapshots of their generated JavaScript. Additional execution tests cover client/SSR/provider output across React, Solid, and Vue, escaping, binding cleanup, HMR, and invalidation.

Measured performance

Complete generated React Start production builds, with 10 server functions per module and seven alternating fresh-process pairs per size:

Server functions	#8523 median	This change median	Reduction	Peak RSS, before → after
100	333.07 ms	326.33 ms	Within noise	329.8 → 324.2 MiB
1,000	886.94 ms	813.09 ms	8.3%	519.9 → 483.2 MiB
5,000	6,682.98 ms	6,048.85 ms	9.5%	883.8 → 849.5 MiB

The candidate wins all seven pairs at 1,000 and 5,000 functions. The 5,000-function fixture is a stress case. Timings include Vite builder creation, transformation, bundling, minification, and writes; they exclude fixture generation, plugin-module loading, and output validation. All RPCs and handlers are retained; client output is byte-identical and server output matches after normalizing build paths and chunk filenames.

Focused compiler measurements show 15.0% faster client transforms, 19.9% faster SSR callers, 27.7% faster providers, and 29.3% faster development providers. The existing smaller e2e app's whole-build result was inconclusive (950.26 → 962.54 ms), so these gains should not be generalized to every app.

Measured on Node 24.8.0 / Apple M3 Max against #8523 at 6c228b37ad, with the extracted candidate on 9148909cc5. The current stack base 3dfc160aee only adds Solid CSS test changes. Full methodology, raw results, and attribution.

Previously completed validation

608 compiler tests and 165 browser tests; TypeScript 5.6–7, ESLint, and package build/export checks passed.
The latest inline-snapshot-only edit passed all eight builder tests.
All 18 bundle scenarios have zero size/chunk-count changes; all 38 emitted client JS files are byte-identical.
No checks were rerun when opening this PR; CI will validate the published branch.

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested code changes locally with the relevant test commands, or tests do not apply to this pull request.
I fully understand the code in this pull request, including any code generated with AI assistance.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

Performance
- Server-function compilation and production builds now run faster in several benchmarked workloads, while preserving equivalent generated output.
Reliability
- Added checks for generated server-function output across React, Solid, and Vue, including client, server-rendering, provider, and development scenarios.
Documentation
- Added guidance and results for compiler and production-build benchmarks.

coderabbitai · 2026-09-27T18:06:49Z

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📥 Commits

Reviewing files that changed from the base of the PR and between 080a540 and c6c33e2.

📒 Files selected for processing (43)

.changeset/fuzzy-berries-behave.md
benchmarks/compiler/README.md
benchmarks/compiler/direct-ast.md
benchmarks/compiler/results/direct-ast-app-output.json
benchmarks/compiler/results/direct-ast-builders-digests.json
benchmarks/compiler/results/direct-ast-builders-timings.json
benchmarks/compiler/results/direct-ast-builds.json
benchmarks/compiler/results/direct-ast-bundle-baseline-hashes.json
benchmarks/compiler/results/direct-ast-bundle-baseline.json
benchmarks/compiler/results/direct-ast-bundle-builders-final-hashes.json
benchmarks/compiler/results/direct-ast-bundle-builders-final.json
benchmarks/compiler/results/direct-ast-bundle-final-hashes.json
benchmarks/compiler/results/direct-ast-bundle-final.json
benchmarks/compiler/results/direct-ast-bundle-pre-attribution.json
benchmarks/compiler/results/direct-ast-caller-digests.json
benchmarks/compiler/results/direct-ast-caller-timings.json
benchmarks/compiler/results/direct-ast-dense-refined-timings.json
benchmarks/compiler/results/direct-ast-digests.json
benchmarks/compiler/results/direct-ast-directives-digests.json
benchmarks/compiler/results/direct-ast-directives-refined-timings.json
benchmarks/compiler/results/direct-ast-directives-timings.json
benchmarks/compiler/results/direct-ast-final-digests.json
benchmarks/compiler/results/direct-ast-final-timings.json
benchmarks/compiler/results/direct-ast-final-verification.json
benchmarks/compiler/results/direct-ast-heavy-builds-100.json
benchmarks/compiler/results/direct-ast-heavy-builds-1000.json
benchmarks/compiler/results/direct-ast-heavy-builds-5000.json
benchmarks/compiler/results/direct-ast-hmr-digests.json
benchmarks/compiler/results/direct-ast-hmr-refined-timings.json
benchmarks/compiler/results/direct-ast-hmr-timings.json
benchmarks/compiler/results/direct-ast-hunk-bundles.json
benchmarks/compiler/results/direct-ast-imports-digests.json
benchmarks/compiler/results/direct-ast-imports-refined-timings.json
benchmarks/compiler/results/direct-ast-imports-timings.json
benchmarks/compiler/results/direct-ast-provider-digests.json
benchmarks/compiler/results/direct-ast-provider-timings.json
benchmarks/compiler/results/direct-ast-timings.json
benchmarks/compiler/server-fn-ast.mjs
benchmarks/compiler/server-fn-build.mjs
packages/start-plugin-core/src/start-compiler/handleCreateServerFn.ts
packages/start-plugin-core/src/start-compiler/serverFnAst.ts
packages/start-plugin-core/tests/createServerFn/generated-ast.test.ts
packages/start-plugin-core/tests/createServerFn/serverFnAst.test.ts

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📝 Walkthrough

Walkthrough

The server-function compiler now builds generated RPC calls, provider wrappers, imports, directives, exports, and HMR statements with AST helpers. New compiler and production-build benchmark harnesses record timing, memory, output comparisons, and bundle hashes. Tests cover generated output across frameworks and runtimes.

Changes

Server-function AST generation and benchmarking

Layer / File(s)	Summary
Build and integrate server-function AST nodes `packages/start-plugin-core/src/start-compiler/serverFnAst.ts`, `packages/start-plugin-core/src/start-compiler/handleCreateServerFn.ts`, `packages/start-plugin-core/tests/createServerFn/*ast.test.ts`, `.changeset/fuzzy-berries-behave.md`	AST helpers create server-function callers, providers, exports, HMR checks, imports, references, and string literals. The compiler uses the helpers instead of parsing generated source strings. Tests cover output and recompilation across frameworks and runtimes.
Measure compiler workloads `benchmarks/compiler/server-fn-ast.mjs`, `benchmarks/compiler/README.md`, `benchmarks/compiler/direct-ast.md`, `benchmarks/compiler/results/direct-ast-*.json`	The compiler benchmark runs selected workloads in baseline and candidate processes, checks source hashes and optional output digests, and records timing and memory data. Documentation and results describe the workloads, measurement protocols, and comparisons.
Measure generated production builds `benchmarks/compiler/server-fn-build.mjs`, `benchmarks/compiler/direct-ast.md`, `benchmarks/compiler/results/direct-ast-app-output.json`, `benchmarks/compiler/results/direct-ast-builds.json`, `benchmarks/compiler/results/direct-ast-heavy-builds-.json`, `benchmarks/compiler/results/direct-ast-bundle--hashes.json`, `benchmarks/compiler/results/direct-ast-hunk-bundles.json`	The build benchmark generates a temporary React Start app, checks client and server outputs, compares normalized hashes, and records build and memory metrics. The report and result files include full-build measurements and bundle comparisons.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to c6c33

The server-function AST change has no identified issue that needs resolution before merging; normal checks remain appropriate.

Security Architecture Review

Security architecture risk: 🔵 Low · up to c6c33

The change affects how server-function code is generated, not an identified authorization rule or deployment boundary. Tests and recorded build comparisons support equivalent output, but they do not establish equivalence for every application.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — A generation regression could propagate to applications using server functions across the supported runtimes. The changed test ranges do not themselves add reachable production entrypoints, and the benchmark fanout does not establish production exposure.

Trust Boundaries and Controls

inferred — The generated client RPC call and server provider meet at a trust boundary, but the reviewed change supplies no evidence of a new attacker-controlled input path, changed authorization control, or increased server authority. Runtime authorization behavior was not independently verified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 9.09% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 6 files. (30 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: constructing compiler-owned server-function AST directly for performance.
Description check	✅ Passed	The description follows the required template, explains the motivation and implementation, documents validation and performance results, and completes the checklist and release-impact sections.

Full details: Docstring Coverage

Explanation

Docstring coverage is 9.09% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 6 files. (30 skipped: 30 unsupported.)

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github-actions · 2026-09-27T18:12:20Z

🚀 Changeset Version Preview

6 package(s) bumped directly, 7 bumped as dependents.

🟥 Major bumps

Package	Version	Reason
`@tanstack/router-plugin`	1.168.41 → 2.0.0	Changeset
`@tanstack/router-utils`	1.162.3 → 2.0.0	Changeset
`@tanstack/start-plugin-core`	1.171.48 → 2.0.0	Changeset

🟩 Patch bumps

Package	Version	Reason
`@tanstack/react-router`	1.170.40 → 1.170.41	Changeset
`@tanstack/react-start-rsc`	0.1.58 → 0.1.59	Changeset
`@tanstack/router-generator`	1.167.39 → 1.167.40	Changeset
`@tanstack/react-start`	1.168.59 → 1.168.60	Dependent
`@tanstack/react-start-client`	1.168.38 → 1.168.39	Dependent
`@tanstack/react-start-server`	1.167.45 → 1.167.46	Dependent
`@tanstack/router-cli`	1.167.39 → 1.167.40	Dependent
`@tanstack/router-vite-plugin`	1.167.41 → 1.167.42	Dependent
`@tanstack/solid-start`	1.168.56 → 1.168.57	Dependent
`@tanstack/vue-start`	1.168.55 → 1.168.56	Dependent

nx-cloud · 2026-09-27T18:15:44Z

View your CI Pipeline Execution ↗ for commit c6c33e2

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:unit,tes...`	✅ Succeeded	25m 52s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	2m 7s	View ↗

☁️ Nx Cloud last updated this comment at 2026-09-27 20:42:27 UTC

github-actions · 2026-09-27T18:17:13Z

Bundle Size Benchmarks

This pull request does not affect bundle size in any measured scenario.

pkg-pr-new · 2026-09-27T18:22:04Z

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commit: c6c33e2

codspeed · 2026-09-27T19:03:53Z

Merging this PR will regress 1 benchmark

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 189 untouched benchmarks
⏩ 3 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Simulation	`hydrate restored route state and mixed Links (react)`	213.2 ms	248.4 ms	-14.18%
⚡	Memory	`mem server streaming-peak chunked (react)`	642.3 KB	349.8 KB	+83.63%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing codex/direct-compiler-ast (c6c33e2) with codex/fuse-clone-provenance (080a540)}

3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Sheraff · 2026-10-11T07:37:55Z

Notes for when this is recut on top of #8504 (now on Yuku 0.19.0), from a review of Yuku's APIs:

Other compiler-owned snippets that fit builders, beyond server functions:
- react-start-rsc/src/plugin/rscCssTransform.ts: the { __tanstackStartRscCss: null } options object and the <>{null}{null}</> fragment, which are parsed then patched behind runtime guards.
- router-plugin/src/core/code-splitter/compilers.ts: the console.warn(...) statement. console is a global, so it needs linkGeneratedReference(node, 'console').
- start-plugin-core/src/start-compiler/handleCreateServerFn.ts: the parseExpression(functionName) identifier.
- start-plugin-core/src/hydrate-when-transform.ts: parseExpression(preloadName) and the <Component {...props} /> child.
Keep template parsing where builders would be 3–10× longer: HMR blocks, the provider's extracted handler, import-protection rewrite.ts, Hydrate lazy imports.
Every builder identifier that refers to a source or import binding must go through linkGeneratedReference, or removeUnusedBindings prunes its import.
Yuku 0.19's generate() prints any single node, so the builder snapshot tests no longer need to wrap nodes in a Program. generateModule now accepts a Node.
b.Property returns ObjectProperty | BindingProperty and b.Literal the whole Literal union, which is why this PR writes ObjectProperty and Directive records by hand. We may ask upstream for precise builders.
parseStatements('') now returns [] without parsing, so the provider-directives call no longer costs an analyze when nothing is missing.

Written with Claude Code (AI-assisted).

github-actions Bot added the package: start-plugin-core label Sep 27, 2026

Sheraff added this pull request to stack #8532 September 27, 2026 20:04

perf(start): construct compiler-owned server function AST directly

c6c33e2

Sheraff force-pushed the codex/direct-compiler-ast branch from 6af7bdf to c6c33e2 Compare September 27, 2026 20:11

Sheraff mentioned this pull request Sep 27, 2026

perf(compiler): reuse immutable cleanup metadata across outputs #8540

Open

4 of 5 tasks

Sheraff mentioned this pull request Oct 10, 2026

feat: migrate Router and Start compilation to Yuku #8504

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perf(start): construct compiler-owned server function AST directly - #8524

perf(start): construct compiler-owned server function AST directly#8524
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