error TS6059: File is not under 'rootDir' is expected to contain all source filesの解決方法

yarn tscをして下記のようなエラーが出たときの対処方法を紹介します。

$ yarn tsc 
error TS6059: File '/test/test.ts' is not under 'rootDir' '/src/index.ts'. 'rootDir' is expected to contain all source files.
  The file is in the program because:
    Matched by default include pattern '**/*'

前提として、このときのファイル構造は下記のようになっています。

.
├── package.json
├── src
│   └── app.ts
├── test
│   └── test.ts
├── tsconfig.json
└── yarn.lock

また、このときのtsconfig.jsonは以下のようになっています。rootDirを指定しているのでよさそうに見えるのですが、これだとダメで、明示的にどれを入れるのか、外すのかを指定してあげる必要があります。

{
  "compilerOptions": {
    "target": "ES6",
    "lib": ["ES6"],                                   /* Specify a set of bundled library declaration files that describe the target runtime environment. */
    "module": "commonjs",                                /* Specify what module code is generated. */
    "rootDir": "src",                                    /* Specify the root folder within your source files. */
    "outDir": "./bin",                                   /* Specify an output folder for all emitted files. */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */
    "noImplicitAny": true,                               /* Enable error reporting for expressions and declarations with an implied 'any' type. */
    "skipLibCheck": true,                                 /* Skip type checking all .d.ts files. */
  },
}

このようにincludeかexcludeを使うと問題を解決できます

{
  "compilerOptions": {
    "target": "ES6",
    "lib": ["ES6"],                                   /* Specify a set of bundled library declaration files that describe the target runtime environment. */
    "module": "commonjs",                                /* Specify what module code is generated. */
    "rootDir": "src",                                    /* Specify the root folder within your source files. */
    "outDir": "./bin",                                   /* Specify an output folder for all emitted files. */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */
    "noImplicitAny": true,                               /* Enable error reporting for expressions and declarations with an implied 'any' type. */
    "skipLibCheck": true,                                 /* Skip type checking all .d.ts files. */
  },
    "include": ["src"]
}

あるいは、 excludeを使います。今回はtest以下は入れたくないので、exclude: ['test']としてやります。

{
  "compilerOptions": {
    "target": "ES6",
    "lib": ["ES6"],                                   /* Specify a set of bundled library declaration files that describe the target runtime environment. */
    "module": "commonjs",                                /* Specify what module code is generated. */
    "rootDir": "src",                                    /* Specify the root folder within your source files. */
    "outDir": "./bin",                                   /* Specify an output folder for all emitted files. */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */
    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */
    "noImplicitAny": true,                               /* Enable error reporting for expressions and declarations with an implied 'any' type. */
    "skipLibCheck": true,                                 /* Skip type checking all .d.ts files. */
  },
    "exclude": ["test"]
}

これでエラーが出なくなります。

参考: error TS6059: File 'xxx/node_modules/typescript/Gulpfile.ts' is not under 'rootDir' #10713