fix: don't add isolateModules to tsconfig when extending from tsconfig with verbatimModuleSyntax

packages/next/src/lib/typescript/writeConfigurationDefaults.ts

@@ -20,7 +20,7 @@ type DesiredCompilerOptionsShape = {
 
 function getDesiredCompilerOptions(
   ts: typeof import('typescript'),
-  userTsConfig?: { compilerOptions?: CompilerOptions }
+  tsOptions?: CompilerOptions
 ): DesiredCompilerOptionsShape {
   const o: DesiredCompilerOptionsShape = {
     // These are suggested values and will be set when not present in the
@@ -80,7 +80,7 @@ function getDesiredCompilerOptions(
       reason: 'to match webpack resolution',
     },
     resolveJsonModule: { value: true, reason: 'to match webpack resolution' },
-    ...(userTsConfig?.compilerOptions?.verbatimModuleSyntax === true
+    ...(tsOptions?.verbatimModuleSyntax === true
       ? undefined
       : {
           isolatedModules: {
@@ -139,7 +139,7 @@ export async function writeConfigurationDefaults(
     isFirstTimeSetup = true
   }
 
-  const desiredCompilerOptions = getDesiredCompilerOptions(ts, userTsConfig)
+  const desiredCompilerOptions = getDesiredCompilerOptions(ts, tsOptions)
 
   const suggestedActions: string[] = []
   const requiredActions: string[] = []

test/integration/tsconfig-verifier/test/index.test.js

@@ -567,6 +567,63 @@ import path from 'path'
     `)
     })
 
+    it('allows you to set verbatimModuleSyntax true via extends without adding isolatedModules', async () => {
+      expect(await exists(tsConfig)).toBe(false)
+      expect(await exists(tsConfigBase)).toBe(false)
+
+      await writeFile(
+        tsConfigBase,
+        `{ "compilerOptions": { "verbatimModuleSyntax": true } }`
+      )
+      await writeFile(tsConfig, `{ "extends": "./tsconfig.base.json" }`)
+      await new Promise((resolve) => setTimeout(resolve, 500))
+      const { code, stderr, stdout } = await nextBuild(appDir, undefined, {
+        stderr: true,
+        stdout: true,
+      })
+      expect(stderr + stdout).not.toContain('isolatedModules')
+      expect(code).toBe(0)
+
+      expect(await readFile(tsConfig, 'utf8')).toMatchInlineSnapshot(`
+        "{
+          \\"extends\\": \\"./tsconfig.base.json\\",
+          \\"compilerOptions\\": {
+            \\"lib\\": [
+              \\"dom\\",
+              \\"dom.iterable\\",
+              \\"esnext\\"
+            ],
+            \\"allowJs\\": true,
+            \\"skipLibCheck\\": true,
+            \\"strict\\": false,
+            \\"noEmit\\": true,
+            \\"incremental\\": true,
+            \\"esModuleInterop\\": true,
+            \\"module\\": \\"esnext\\",
+            \\"moduleResolution\\": \\"node\\",
+            \\"resolveJsonModule\\": true,
+            \\"jsx\\": \\"preserve\\",
+            \\"plugins\\": [
+              {
+                \\"name\\": \\"next\\"
+              }
+            ],
+            \\"strictNullChecks\\": true
+          },
+          \\"include\\": [
+            \\"next-env.d.ts\\",
+            \\".next/types/**/*.ts\\",
+            \\"**/*.ts\\",
+            \\"**/*.tsx\\"
+          ],
+          \\"exclude\\": [
+            \\"node_modules\\"
+          ]
+        }
+        "
+      `)
+    })
+
     it('allows you to extend another configuration file', async () => {
       expect(await exists(tsConfig)).toBe(false)
       expect(await exists(tsConfigBase)).toBe(false)