feat: add import.meta.main support in config (bundle config loader) (vitejs#20516)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: sapphi-red <[email protected]>

Author: Copilot

packages/vite/src/node/__tests__/config.spec.ts

@@ -803,6 +803,20 @@ describe('loadConfigFromFile', () => {
       `)
   })
 
+  test('import.meta.main is correctly set', async () => {
+    const { config } = (await loadConfigFromFile(
+      {} as any,
+      path.resolve(fixtures, './import-meta/vite.config.ts'),
+      path.resolve(fixtures, './import-meta'),
+    ))!
+
+    const c = config as any
+    expect(c.isMain).toBe(false)
+    expect(c.url).toContain('file://')
+    expect(c.dirname).toContain('import-meta')
+    expect(c.filename).toContain('vite.config.ts')
+  })
+
   describe('loadConfigFromFile with configLoader: native', () => {
     const fixtureRoot = path.resolve(fixtures, './native-import')
 

packages/vite/src/node/__tests__/fixtures/config/import-meta/vite.config.ts

@@ -0,0 +1,6 @@
+export default {
+  isMain: import.meta.main,
+  url: import.meta.url,
+  dirname: import.meta.dirname,
+  filename: import.meta.filename,
+}

packages/vite/src/node/config.ts

@@ -1941,6 +1941,7 @@ async function bundleConfigFile(
       'import.meta.url': importMetaUrlVarName,
       'import.meta.dirname': dirnameVarName,
       'import.meta.filename': filenameVarName,
+      'import.meta.main': 'false',
     },
     plugins: [
       {