fix: improve tsconfig extends checks

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

@@ -223,10 +223,33 @@ export async function writeConfigurationDefaults(
         )
     )
   } else if (hasAppDir && !rawConfig.include.includes(nextAppTypes)) {
-    userTsConfig.include.push(nextAppTypes)
-    suggestedActions.push(
-      cyan('include') + ' was updated to add ' + bold(`'${nextAppTypes}'`)
-    )
+    if (!Array.isArray(userTsConfig.include)) {
+      userTsConfig.include = []
+    }
+    // rawConfig will resolve all extends and include paths (ex: tsconfig.json, tsconfig.base.json, etc.)
+    // if it doesn't match userTsConfig then update the userTsConfig to add the
+    // rawConfig's includes in addition to nextAppTypes
+    if (
+      rawConfig.include.length !== userTsConfig.include.length ||
+      JSON.stringify(rawConfig.include.sort()) !==
+        JSON.stringify(userTsConfig.include.sort())
+    ) {
+      userTsConfig.include.push(...rawConfig.include, nextAppTypes)
+      suggestedActions.push(
+        cyan('include') +
+          ' was set to ' +
+          bold(
+            `[${[...rawConfig.include, nextAppTypes]
+              .map((i) => `'${i}'`)
+              .join(', ')}]`
+          )
+      )
+    } else {
+      userTsConfig.include.push(nextAppTypes)
+      suggestedActions.push(
+        cyan('include') + ' was updated to add ' + bold(`'${nextAppTypes}'`)
+      )
+    }
   }
 
   // Enable the Next.js typescript plugin.
@@ -270,14 +293,13 @@ export async function writeConfigurationDefaults(
       )
     }
 
-    // If `strict` is set to `false` or `strictNullChecks` is set to `false`,
+    // If `strict` is set to `false` and `strictNullChecks` is set to `false`,
     // then set `strictNullChecks` to `true`.
     if (
       hasPagesDir &&
       hasAppDir &&
-      userTsConfig.compilerOptions &&
-      !userTsConfig.compilerOptions.strict &&
-      !('strictNullChecks' in userTsConfig.compilerOptions)
+      !tsOptions.strict &&
+      !('strictNullChecks' in tsOptions)
     ) {
       userTsConfig.compilerOptions.strictNullChecks = true
       suggestedActions.push(

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

@@ -695,8 +695,7 @@ import path from 'path'
         "{
           "extends": "./tsconfig.base.json",
           "compilerOptions": {
-            "target": "ES2017",
-            "strictNullChecks": true
+            "target": "ES2017"
           }
         }
         "
@@ -764,8 +763,7 @@ import path from 'path'
           "extends": "./tsconfig.base.json",
           "compilerOptions": {
             "target": "ES2017",
-            "incremental": true,
-            "strictNullChecks": true
+            "incremental": true
           }
         }
         "

test/unit/write-configuration-defaults.test.ts

@@ -0,0 +1,102 @@
+/* eslint-env jest */
+import fs from 'fs-extra'
+import { join } from 'path'
+import { writeConfigurationDefaults } from 'next/dist/lib/typescript/writeConfigurationDefaults'
+import * as ts from 'typescript'
+
+const fixtureDir = join(__dirname, 'fixtures/config-ts')
+const tsconfigFile = join(fixtureDir, 'tsconfig.json')
+const tsconfigBaseFile = join(fixtureDir, 'tsconfig.base.json')
+const distDir = '.next'
+const nextAppTypes = `${distDir}/types/**/*.ts`
+
+describe('tsconfig.base.json', () => {
+  beforeEach(async () => {
+    await fs.ensureDir(fixtureDir)
+  })
+  afterEach(async () => {
+    await fs.remove(tsconfigFile)
+    await fs.remove(tsconfigBaseFile)
+  })
+
+  describe('appDir', () => {
+    it('should support empty includes when base provides it', async () => {
+      const include = ['**/*.ts', '**/*.tsx', nextAppTypes]
+      const content = {
+        extends: './tsconfig.base.json',
+      }
+      const baseContent = {
+        include,
+      }
+
+      await fs.writeFile(tsconfigFile, JSON.stringify(content, null, 2))
+      await fs.writeFile(tsconfigBaseFile, JSON.stringify(baseContent, null, 2))
+
+      await expect(
+        writeConfigurationDefaults(ts, tsconfigFile, false, true, distDir, true)
+      ).resolves.not.toThrow()
+
+      const output = await fs.readFile(tsconfigFile, 'utf8')
+      const parsed = JSON.parse(output)
+
+      expect(parsed.include).toBeUndefined()
+    })
+
+    it('should replace includes when base is missing appTypes', async () => {
+      const include = ['**/*.ts', '**/*.tsx']
+      const content = {
+        extends: './tsconfig.base.json',
+      }
+      const baseContent = {
+        include,
+      }
+
+      await fs.writeFile(tsconfigFile, JSON.stringify(content, null, 2))
+      await fs.writeFile(tsconfigBaseFile, JSON.stringify(baseContent, null, 2))
+
+      await expect(
+        writeConfigurationDefaults(ts, tsconfigFile, false, true, distDir, true)
+      ).resolves.not.toThrow()
+
+      const output = await fs.readFile(tsconfigFile, 'utf8')
+      const parsed = JSON.parse(output)
+
+      expect(parsed.include.sort()).toMatchInlineSnapshot(`
+        [
+          "**/*.ts",
+          "**/*.tsx",
+          ".next/types/**/*.ts",
+        ]
+      `)
+    })
+
+    it('should not add strictNullChecks if base provides it', async () => {
+      const content = {
+        extends: './tsconfig.base.json',
+      }
+
+      const baseContent = {
+        compilerOptions: {
+          strictNullChecks: true,
+          strict: true,
+        },
+      }
+
+      await fs.writeFile(tsconfigFile, JSON.stringify(content, null, 2))
+      await fs.writeFile(tsconfigBaseFile, JSON.stringify(baseContent, null, 2))
+
+      await writeConfigurationDefaults(
+        ts,
+        tsconfigFile,
+        false,
+        true,
+        distDir,
+        true
+      )
+      const output = await fs.readFile(tsconfigFile, 'utf8')
+      const parsed = JSON.parse(output)
+
+      expect(parsed.compilerOptions.strictNullChecks).toBeUndefined()
+    })
+  })
+})