Suggestion: an option to make --showConfig more verbose

Search Terms

showConfig, verbose, verbosity

Suggestion

Currently, the --showConfig option will only print the compiler options that are provided by the given tsconfig.json.

The suggestion is to introduce another command line option to use together with --showConfig, for example --verbose, that would additionally print out the default values of all of the missing compiler options.

Use Cases

This new option hopes to make debugging configuration files easier by explicitly displaying the value of every compiler option.

Examples

Given the following folder structure:

.
├── main.ts
└── tsconfig.json

And the following tsconfig.json:

{
  "compilerOptions": {
    "target": "es5"
  },
  "include": ["**/*.ts"]
}

Running the command tsc --showConfig produces:

{
    "compilerOptions": {
        "target": "es5"
    },
    "files": [
        "./main.ts"
    ],
    "include": [
        "**/*.ts"
    ]
}

Here's an example output of tsc --showConfig --verbose. It was derived in the following way:

1. Use the Typescript Handbook's table of compiler options and their defaults as a reference.
2. Exclude deprecated options (out, reactNamespace, and skipDefaultLibCheck)
3. Also exclude any options that are missing a default value in the table, since JSON doesn't have a notion of undefined.

{
    "compilerOptions": {
        "allowJs": false,
        "allowSyntheticDefaultImports": false,
        "allowUmdGlobalAccess": false,
        "allowUnreachableCode": false,
        "allowUnusedLabels": false,
        "alwaysStrict": false,
        "build": false,
        "charset": "utf8",
        "checkJs": false,
        "composite": true,
        "declaration": false,
        "declarationMap": false,
        "diagnostics": false,
        "disableSizeLimit": false,
        "downlevelIteration": false,
        "emitBOM": false,
        "emitDeclarationOnly": false,
        "emitDecoratorMetadata": false,
        "esModuleInterop": false,
        "experimentalDecorators": false,
        "extendedDiagnostics": false,
        "forceConsistentCasingInFileNames": false,
        "importHelpers": false,
        "incremental": false,
        "inlineSourceMap": false,
        "inlineSources": false,
        "isolatedModules": false,
        "jsx": "preserve",
        "jsxFactory": "React.createElement",
        "keyofStringsOnly": false,
        "listEmittedFiles": false,
        "listFiles": false,
        "locale": "en", // [2]
        "module": "commonjs",
        "moduleResolution": "classic",
        "newLine": "lf", // [2]
        "noEmit": false,
        "noEmitHelpers": false,
        "noEmitOnError": false,
        "noErrorTruncation": false,
        "noFallthroughCasesInSwitch": false,
        "noImplicitAny": false,
        "noImplicitReturns": false,
        "noImplicitThis": false,
        "noImplicitUseStrict": false,
        "noLib": false,
        "noResolve": false,
        "noStrictGenericChecks": false,
        "noUnusedLocals": false,
        "noUnusedParameters": false,
        "preserveConstEnums": false,
        "preserveSymlinks": false,
        "preserveWatchOutput": false,
        "pretty": true, // [1]
        "removeComments": false,
        "resolveJsonModule": false,
        "rootDir": "(computed from the list of input files)", // [3]
        "showConfig": false,
        "skipLibCheck": false,
        "sourceMap": false,
        "strict": false,
        "strictBindCallApply": false,
        "strictFunctionTypes": false,
        "strictPropertyInitialization": false,
        "strictNullChecks": false,
        "suppressExcessPropertyErrors": false,
        "suppressImplicitAnyIndexErrors": false,
        "target": "es5",
        "traceResolution": false,
        "tsBuildInfoFile": ".tsbuildinfo"
    },
    "files": [
        "./main.ts"
    ],
    "include": [
        "**/*.ts"
    ]
}

^[1] The Handbook says pretty should be true unless piping or redirecting output to file, so the desired value here may be ambiguous?

^[2] locale and newLine are platform-specific.

^[3] rootDir would need to be calculated so it can be displayed.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Start by reviewing the existing tsc --showConfig behavior and the Handbook's compiler-option defaults referenced in the issue. Define how --verbose should represent platform-specific, computed, deprecated, and undefined options; done means the command consistently displays the intended defaults without changing ordinary --showConfig output. No source files or tests are named.