fix: use the classic JSX runtime for the Vite 8 dep scan (#262)

.changeset/vite8-scan-jsx-classic.md

@@ -0,0 +1,16 @@
+---
+'vite-plugin-solid': patch
+---
+
+Vite 8's dependency scan no longer breaks on `.tsx` files (issue #262).
+The plugin previously set `optimizeDeps.rolldownOptions.transform.jsx:
+'preserve'` to stop Rolldown from injecting `react/jsx-dev-runtime`
+imports during the scan — but the scanner re-parses the transformed
+output as plain JS (`import.meta.glob` handling force-tags modules as
+`js`), so any `.tsx` with JSX was a hard `PARSE_ERROR: Unexpected JSX
+expression` that aborted the whole scan and skipped pre-bundling. The
+scan transform now uses the classic JSX runtime, which lowers JSX to bare
+`React.createElement` calls without injecting any import: the scan output
+is never executed, it only exists so rolldown can walk the import graph,
+so the undefined identifier is harmless. Backport of the fix already on
+the 3.0.0-next line.

src/index.ts

@@ -281,10 +281,15 @@ export default function solidPlugin(options: Partial<Options> = {}): Plugin {
           exclude: solidPkgsConfig.optimizeDeps.exclude,
           // Vite 8+ uses Rolldown for dependency scanning. Rolldown defaults to
           // React's automatic JSX runtime for .tsx files, injecting a
-          // react/jsx-dev-runtime import. Tell it to preserve JSX as-is since
-          // this plugin handles JSX transformation via babel-preset-solid.
+          // react/jsx-dev-runtime import that fails to resolve and aborts the
+          // scan. 'preserve' is no fix: the scanner re-parses the transformed
+          // output as plain JS, so any preserved JSX is a hard parse error
+          // (issue #262). The classic runtime is the only scan-safe lowering:
+          // it emits bare `React.createElement` calls without injecting any
+          // import, and the scan output is never executed — it only exists so
+          // rolldown can walk the import graph.
           ...(isVite8OrNewer
-            ? { rolldownOptions: { transform: { jsx: 'preserve' as const } } }
+            ? { rolldownOptions: { transform: { jsx: { runtime: 'classic' as const } } } }
             : {}),
         },
         ...(!isVite6OrNewer ? { ssr: solidPkgsConfig.ssr } : {}),