unplugin: support SolidStart / vinxi filesystem routers

[STRd6]

Fixes #1319 (same report as solid-start#1549).

Cause: two independent breaks.

1. vinxi's filesystem routers (analyzeModule) enumerate a route module's exports by reading the file raw off disk and parsing it with esbuild's tsx loader. Civet source fails to parse, addRoute swallows the error, and the route is silently dropped — before any vite plugin runs.
2. The plugin's .civet → .civet.tsx id rewrite breaks vinxi's manifest correspondence: route chunks are looked up in vite's build manifest by the original .civet?pick=... path, crashing prod SSR with Cannot read properties of undefined (reading 'file').

Approach:

• Wrap each vinxi fs-router's toRoute to compile .civet routes to TSX and substitute fs.readFileSync (exact-path match, restored in finally) for the duration of the analysis. Hooked from the vite config hook (enforce: 'pre' runs before vinxi's hook that first materializes routes) and from a construction-time microtask via globalThis.app, because vinxi build builds each router in a subprocess while the parent also materializes routes without running any vite hook.
• Skip the output-extension append when a vinxi router is detected (same shape as the existing esbuild carve-out). JSX still compiles because SolidStart forwards extensions to vite-plugin-solid.
• Warn on ts: "preserve" under vinxi: with .civet ids, neither vite core nor vite-plugin-solid strips TypeScript syntax, so output must be type-free (civet / esbuild / tsc).

Includes a SolidStart example (integration/unplugin-examples/solid-start) with a Civet page route and API route — verified with vinxi build + serving the output, and vinxi dev — plus unit tests for the router patching and id behavior, and README/docs updates.

Longer term this wants an upstream analysis hook (sketched in the linked solid-start issue discussion); this fix works without one and could feature-detect it later.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2d68a3b) to head (f3033ab).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%            
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  Files           57        57            
  Lines        28023     28134   +111     
  Branches      5255      5281    +26     
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+ Hits         28023     28134   +111     

Files with missing lines	Coverage Δ
source/unplugin/unplugin.civet	100.00% <100.00%> (ø)

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[greptile-apps]

Greptile Summary

This PR adds SolidStart/vinxi filesystem-router compatibility to the Civet unplugin. Two independent issues are fixed: vinxi's analyzeModule reads routes synchronously off disk as TSX (rejecting raw Civet source), and the .civet → .civet.tsx id rewrite broke vinxi's build-manifest lookup at prod SSR time.

• Route analysis shim: patchVinxiFsRouter wraps each router's toRoute to pre-compile .civet routes to TSX and temporarily substitute fs.readFileSync via a single module-level intercept backed by a Map<string, string>, making concurrent analyses safe. The patch runs from the vite config hook (for dev/build subprocesses) and from a construction-time queueMicrotask (for vinxi build's parent-process manifest pass where no vite hook fires).
• Id rewrite bypass: resolveId skips appending the output extension when a vinxi router is detected (vinxi = true), matching how the esbuild framework already skips it; SolidStart's extensions forwarding to vite-plugin-solid handles JSX compilation via the id suffix instead.
• A minimal SolidStart example app with a page route and API route, comprehensive unit tests for the patching/concurrency/restore semantics, and README/docs updates are included.

Confidence Score: 5/5

Safe to merge. The two root-cause fixes are well-scoped, the concurrency-sensitive fs.readFileSync intercept uses a correct Map+refcount pattern, and the change is covered by ten new unit tests.

Both bugs are addressed with targeted, independently testable changes. The module-level readFileSync intercept correctly handles concurrent toRoute calls. The vinxi flag is set only from the vite config hook, which is intentional. No pre-existing behavior is altered for non-vinxi users.

No files require special attention.

Important Files Changed

Filename	Overview
source/unplugin/unplugin.civet	Core of the fix: adds module-level concurrent-safe fs.readFileSync intercept, patchVinxiFsRouter wrapper, queueMicrotask global-app probe, vinxi flag, and output-extension bypass in resolveId/handleHotUpdate. Logic is correct; previous concurrency issue was already resolved via Map+counter approach.
test/infra/unplugin.civet	New describe block adds 10 targeted tests covering router patching, compiled-TSX substitution, concurrent analyses, intercept restoration, globalThis.app microtask path, non-civet passthrough, idempotent patching, and the preserve-mode warning.
integration/unplugin-examples/solid-start/app.config.ts	Minimal SolidStart config: ts:"civet" (correct — ts:"preserve" is now explicitly unsupported with vinxi), extensions:["civet"] for filesystem router scan, and the Civet vite plugin.
integration/unplugin-examples/solid-start/src/routes/index.civet	Example page route — valid Civet with a JSX default export. Demonstrates the filesystem router integration working end-to-end.
integration/unplugin-examples/solid-start/src/routes/api/answer.civet	Example API route — exports a GET handler using SolidStart's json helper. Validates the named-export path through vinxi's analyzeModule shim.

_{Reviews (2): Last reviewed commit: "unplugin: review feedback — refcounted i..." | Re-trigger Greptile}

[edemaine]

Thanks for taking this on! Are you working on an upstream patch too?

I thought Tanstack Start used Vinxi, but apparently they migrated away last year. Nonetheless, we should probably test Tanstack Start with the unplugin at some point.

[STRd6]

Are you working on an upstream patch too?

Yes: solidjs/solid-start#2156

[edemaine]

@greptileai revise your review