feat(ssr): add import.meta.main support for Node.js module runner (vitejs#20517)

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

Author: Copilot

packages/vite/src/module-runner/createImportMeta.ts

@@ -54,6 +54,7 @@ export async function createNodeImportMeta(
 
   return {
     ...defaultMeta,
+    main: false,
     resolve(id: string, parent?: string) {
       const resolver = importMetaResolver ?? defaultMeta.resolve
       return resolver(id, parent ?? href)

playground/ssr/__tests__/ssr.spec.ts

@@ -52,6 +52,12 @@ test(`import.meta.resolve is supported`, async () => {
   expect(await page.textContent('.import-meta-resolve')).toBe(metaUrl)
 })
 
+test(`import.meta.main is supported`, async () => {
+  await page.goto(`${url}/import-meta`)
+
+  expect(await page.textContent('.import-meta-main')).toBe('false')
+})
+
 test.runIf(isServe)('html proxy is encoded', async () => {
   await page.goto(
     `${url}?%22%3E%3C/script%3E%3Cscript%3Econsole.log(%27html%20proxy%20is%20not%20encoded%27)%3C/script%3E`,

playground/ssr/src/app.js

@@ -65,8 +65,10 @@ async function renderForkedDeadlockDynamicImports(rootDir) {
 async function renderImportMeta(rootDir) {
   const metaUrl = import.meta.url
   const resolveResult = import.meta.resolve('./app.js')
+  const metaMain = import.meta.main
   return (
     `<div class="import-meta-url">${escapeHtml(metaUrl)}</div>` +
-    `<div class="import-meta-resolve">${escapeHtml(resolveResult)}</div>`
+    `<div class="import-meta-resolve">${escapeHtml(resolveResult)}</div>` +
+    `<div class="import-meta-main">${escapeHtml(String(metaMain))}</div>`
   )
 }