fix(start-plugin-core): register server functions reachable only through provider modules by maricastroc · Pull Request #8732 · TanStack/router

maricastroc · 2026-10-16T13:14:16Z

🎯 Changes

A caller module drops its handler bodies, so imports that only those handlers used are dead-code-eliminated. A module whose server functions are only referenced from inside another server function's handler therefore never enters the client or SSR caller graph — it is reachable only through the provider modules (…?tss-serverfn-split), and those are imported by the resolver manifest itself.

The manifest is generated in the load hook of #tanstack-start-server-fn-resolver, before the bundler loads the providers it lists, so those nested server functions were discovered too late to be in it:

# before, in e2e/react-start/server-functions
$ grep -o 'functionName: "[^"]*"' dist/server/server.js | sort -u | wc -l
63   # fnOnlyCalledByServer_createServerFn_handler missing
$ curl .../_serverFn/84594005…
Server function info not found for 954baed5…

Dev is unaffected because its resolver decodes the file and export name out of the id instead of consulting a manifest, and Rsbuild already rebuilds the resolver module on finishMake (64 entries for the same app).

So the manifest now loads the provider modules and what they reach first, re-seeding from any server function those loads register, until nothing new appears. Failures while crawling are ignored: those modules report their own errors when the bundler loads them through their real importer. The crawl stays inside first-party code (it skips virtual modules, /node_modules/ and non-module ids), so a server function declared in a dependency and called only from another handler is still missed, as before.

Validation

@tanstack/start-plugin-core: test:unit (856), test:types, test:eslint.
tanstack-react-start-e2e-server-functions: test:e2e (vite + rsbuild modes), with a new spec for the /server-only-fn route, which existed with no test.
New tests/vite/server-fn-manifest.test.ts builds a server bundle with the real plugin and calls the built entry in Node. Its two nested cases fail on main with Server function info not found; the direct-call control passes there.
Built rsc, import-protection and basic e2e apps (the RSC app exercises a separate provider environment).
dist/client of the server-functions app is byte-identical to a build without the change; dist/server grows 929 B (+0.19%), the provider module that was missing.

✅ 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

Bug Fixes
- Fixed production builds so server functions called indirectly by other server functions resolve correctly, including functions reached through multiple levels of calls or bundled dependencies.
- Preserved resolution for server functions called directly by an app entry point and for builds with externalized dependencies.
- Verified that server-only functions invoked from a page display the expected result.

…ugh provider modules The Vite resolver manifest was generated before the server-function provider modules it imports were loaded, so a server function only called from inside another server function's handler was missing from it and failed at runtime with `Server function info not found`.

changeset-bot · 2026-10-16T13:14:24Z

🦋 Changeset detected

Latest commit: c0bc27d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@tanstack/start-plugin-core	Patch
@tanstack/react-start-rsc	Patch
@tanstack/react-start	Patch
@tanstack/solid-start	Patch
@tanstack/vue-start	Patch

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coderabbitai · 2026-10-16T13:15:12Z

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📒 Files selected for processing: 4

packages/start-plugin-core/src/vite/start-compiler-plugin/plugin.ts
packages/start-plugin-core/src/vite/start-compiler-plugin/server-fn-discovery.ts
packages/start-plugin-core/tests/vite/server-fn-discovery.test.ts
packages/start-plugin-core/tests/vite/server-fn-manifest.test.ts

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📝 Walkthrough

The Vite compiler now discovers server functions in provider modules and their reachable dependencies before generating the resolver manifest. Tests cover dependency traversal, production builds, development compilation, and the /server-only-fn end-to-end flow.

Changes: Server-function manifest discovery

Layer / File(s)	Summary
Provider dependency traversal `packages/start-plugin-core/src/vite/start-compiler-plugin/server-fn-discovery.ts`, `packages/start-plugin-core/tests/vite/server-fn-discovery.test.ts`	The discovery function traverses eligible static and dynamic imports, then rescans the server-function registry. Tests cover traversal, filtering, repeated modules, dependencies, and load failures.
Manifest generation and build validation `packages/start-plugin-core/src/vite/start-compiler-plugin/plugin.ts`, `packages/start-plugin-core/tests/vite/server-fn-manifest.test.ts`, `e2e/react-start/server-functions/tests/server-functions.spec.ts`, `.changeset/server-fn-provider-graph-manifest.md`	The manifest loader awaits provider discovery before generation. Build, development-mode, and end-to-end tests cover server-only function calls. A patch changeset records the update.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant Compiler as Start compiler plugin
  participant Discovery as discoverProviderServerFns
  participant Vite as Vite load and resolve hooks
  participant Registry as serverFnsById
  participant Manifest as Resolver manifest generator
  Compiler->>Discovery: Pass Vite hooks and server-function registry
  Discovery->>Vite: Load provider and dependency modules
  Vite-->>Discovery: Return module imports and resolutions
  Discovery->>Registry: Register discovered server functions
  Discovery-->>Compiler: Complete provider discovery
  Compiler->>Manifest: Generate resolver manifest

Suggested reviewers: schiller-manuel

Merge Risk: ⚪ Minimal · up to c0bc2

This change registers server functions reachable only through other server functions, fixing production runtime failures. The author reports unit, type, lint, and e2e tests passing. No actionable merge-blocking risk remains.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main fix: registering server functions reachable only through provider modules.
Description check		The description includes the required Changes, Checklist, and Release Impact sections. It explains the motivation, implementation, validation, and changeset impact, with all applicable checklist items…
Linked Issues check		Issue `#8731` requires a nested server function to resolve in a production build when the client does not call it. The resolver load hook now discovers provider modules and their reachable modules befor…
Out of Scope Changes check		The changes stay within issue `#8731`. The discovery code, manifest integration, regression tests, E2E test, and changeset support or document production resolution of server-only nested functions. Bund…

Full details: Description check

Explanation

The description includes the required Changes, Checklist, and Release Impact sections. It explains the motivation, implementation, validation, and changeset impact, with all applicable checklist items completed.

Full details: Linked Issues check

Explanation

Issue #8731 requires a nested server function to resolve in a production build when the client does not call it. The resolver load hook now discovers provider modules and their reachable modules before it generates the manifest. The discovery repeats after newly registered server functions appear and skips external or non-module IDs. Integration tests execute direct nesting, multi-level nesting, and a bundled dependency case against a built server entry. The E2E test covers the server-only route.

Full details: Out of Scope Changes check

Explanation

The changes stay within issue #8731. The discovery code, manifest integration, regression tests, E2E test, and changeset support or document production resolution of server-only nested functions. Bundled-dependency coverage addresses the same provider-module discovery path. No unrelated product behavior is demonstrated.

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Actionable comments posted: 1

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Inline comments:
Review comments at
@packages/start-plugin-core/src/vite/start-compiler-plugin/server-fn-discovery.ts:
- Line 15: Update the module-ID filter in server-function discovery so it skips
externalized dependencies rather than rejecting every path containing
/node_modules/, allowing ssr.noExternal packages with server functions to be
discovered. Add a build test where another handler is the only caller of a
server function in a bundled dependency, and verify discovery includes it in the
generated manifest.

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📥 Commits

Reviewing files that changed from the base of the PR and between 7a06725 and 5d4b6b2.

📒 Files selected for processing: 6

.changeset/server-fn-provider-graph-manifest.md
e2e/react-start/server-functions/tests/server-functions.spec.ts
packages/start-plugin-core/src/vite/start-compiler-plugin/plugin.ts
packages/start-plugin-core/src/vite/start-compiler-plugin/server-fn-discovery.ts
packages/start-plugin-core/tests/vite/server-fn-discovery.test.ts
packages/start-plugin-core/tests/vite/server-fn-manifest.test.ts

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…ction discovery Discovery skipped every module under node_modules, so a server function declared in a dependency bundled through ssr.noExternal was missing from the resolver manifest. Externalized dependencies show up as bare specifiers and passed that check, and loading an external id never settles, which hung the build. Ask the resolver whether each import is external instead of checking its path.

coderabbitai Bot reviewed Oct 16, 2026

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Comment thread packages/start-plugin-core/src/vite/start-compiler-plugin/server-fn-discovery.ts Outdated

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fix(start-plugin-core): register server functions reachable only through provider modules - #8732

fix(start-plugin-core): register server functions reachable only through provider modules#8732
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maricastroc:fix/server-fn-nested-provider-manifest

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