Stop the frontend watch from rebuilding in a loop

src/Elastic.Documentation.Site/vite.config.test.ts

@@ -0,0 +1,41 @@
+/**
+ * @jest-environment node
+ */
+import type { UserConfig } from 'vite'
+
+jest.mock('vite', () => ({ defineConfig: (config: unknown) => config }))
+jest.mock('@tailwindcss/vite', () => () => ({ name: 'tailwindcss' }))
+jest.mock('@vitejs/plugin-react', () => () => ({ name: 'react' }))
+jest.mock('vite-plugin-svgr', () => () => ({ name: 'svgr' }))
+
+const loadConfig = async (argv: string[]): Promise<UserConfig> => {
+    const originalArgv = process.argv
+    process.argv = ['node', 'vite', ...argv]
+    try {
+        let config: UserConfig = {}
+        await jest.isolateModulesAsync(async () => {
+            config = (await import('./vite.config')).default as UserConfig
+        })
+        return config
+    } finally {
+        process.argv = originalArgv
+    }
+}
+
+describe('vite.config build.watch', () => {
+    it('leaves watch unset for a one-shot build so `vite build` exits', async () => {
+        const config = await loadConfig(['build'])
+
+        expect(config.build?.watch).toBeNull()
+    })
+
+    it('excludes the build output under --watch so writes do not trigger a rebuild', async () => {
+        const config = await loadConfig(['build', '--watch'])
+
+        expect(config.build?.watch).toEqual(
+            expect.objectContaining({
+                exclude: expect.arrayContaining(['**/_static/**']),
+            })
+        )
+    })
+})

src/Elastic.Documentation.Site/vite.config.ts

@@ -30,6 +30,12 @@ export default defineConfig({
         sourcemap: true,
         // Razor resolves `main.js` to the hashed entry through `.vite/manifest.json`.
         manifest: true,
+        // Tailwind's content globs match the built `_static/*.js`, and the plugin watches every
+        // scanned file, so without this each `vite build --watch` output triggers another build.
+        // Only set under --watch: any non-null value turns a plain `vite build` into a watcher.
+        watch: process.argv.includes('--watch')
+            ? { exclude: ['**/_static/**', '**/node_modules/**'] }
+            : null,
         rollupOptions: {
             input: {
                 main: path.resolve(__dirname, 'Assets/main.ts'),