Configuration inheritance

Often a project has multiple output targets, e.g. ES5 and ES2015, debug and production or CommonJS and System;Just a few configuration options change between these two targets, and maintaining multiple tsconfig.json files can be a hassle.

TypeScript 2.1 supports inheriting configuration using extends, where:

• extends is a new top-level property in tsconfig.json (alongside compilerOptions, files, include, and exclude).
• The value of extends must be a string containing a path to another configuration file to inherit from.
• The configuration from the base file are loaded first, then overridden by those in the inheriting config file.
• Circularity between configuration files is not allowed.
• files, include and exclude from the inheriting config file overwrite those from the base config file.
• All relative paths found in the configuration file will be resolved relative to the configuration file they originated in.

Example

configs/base.json:

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true
  }
}

tsconfig.json:

{
  "extends": "./configs/base",
  "files": [
    "main.ts",
    "supplemental.ts"
  ]
}

tsconfig.nostrictnull.json:

{
  "extends": "./tsconfig",
  "compilerOptions": {
    "strictNullChecks": false
  }
}