From f910ca8f1276631a7cae7dff726f65e50337222b Mon Sep 17 00:00:00 2001
From: Emil Persson <emil.persson@creuna.se>
Date: Tue, 17 Jan 2017 21:23:29 +0100
Subject: [PATCH] Add ability to resolve "extends" directive in tsconfig.json

---
 src/utils.ts                                  | 11 +++++--
 tests/__tests__/tsconfig-string.spec.ts       | 33 ++++++++++++++++++-
 tests/__ts-jest-mocks__/path.ts               | 12 ++++---
 tests/tsconfig-test/extends-tsconfig.json     |  3 ++
 .../extends-with-overrides-tsconfig.json      |  7 ++++
 5 files changed, 59 insertions(+), 7 deletions(-)
 create mode 100644 tests/tsconfig-test/extends-tsconfig.json
 create mode 100644 tests/tsconfig-test/extends-with-overrides-tsconfig.json

diff --git a/src/utils.ts b/src/utils.ts
index 485865494d..3f6da23d6a 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -73,7 +73,14 @@ export function getTSConfig(globals, collectCoverage: boolean = false) {
     config = 'tsconfig.json';
   }
   if (typeof config === 'string') {
-    config = require(path.resolve(config)).compilerOptions;
+    const configPath = path.resolve(config);
+    const external = require(configPath);
+    config = external.compilerOptions || {};
+
+    if (typeof external.extends === 'string') {
+      const parentConfigPath = path.join(path.dirname(configPath), external.extends);
+      config = Object.assign({}, require(parentConfigPath).compilerOptions, config);
+    }
   }
   config.module = config.module || tsc.ModuleKind.CommonJS;
   config.jsx = config.jsx || tsc.JsxEmit.React;
@@ -89,4 +96,4 @@ export function getTSConfig(globals, collectCoverage: boolean = false) {
   }
 
   return tsc.convertCompilerOptionsFromJson(config, undefined).options;
-}
\ No newline at end of file
+}
diff --git a/tests/__tests__/tsconfig-string.spec.ts b/tests/__tests__/tsconfig-string.spec.ts
index fccc4fb621..4cf6de6289 100644
--- a/tests/__tests__/tsconfig-string.spec.ts
+++ b/tests/__tests__/tsconfig-string.spec.ts
@@ -52,4 +52,35 @@ describe('get ts config from string', () => {
     });
   });
 
-});
\ No newline at end of file
+  it('should correctly resolve the "extends" directive', () => {
+    const {getTSConfig} = require('../../src/utils');
+    const result = getTSConfig({
+      '__TS_CONFIG__': 'extends-tsconfig.json'
+    });
+
+    expect(result).toEqual ({
+      'target': 2,
+      'module': 1,
+      'moduleResolution': 2,
+      'noEmitOnError': true,
+      'jsx': 2
+    });
+  });
+
+  it('should correctly override any config in the "extends" directive', () => {
+    const {getTSConfig} = require('../../src/utils');
+    const result = getTSConfig({
+      '__TS_CONFIG__': 'extends-with-overrides-tsconfig.json'
+    });
+
+    expect(result).toEqual ({
+      'target': 1,
+      'module': 1,
+      'moduleResolution': 2,
+      'noEmitOnError': true,
+      'jsx': 2,
+      'noImplicitAny': true
+    });
+  });
+
+});
diff --git a/tests/__ts-jest-mocks__/path.ts b/tests/__ts-jest-mocks__/path.ts
index f3ad8e7735..9a3474b60a 100644
--- a/tests/__ts-jest-mocks__/path.ts
+++ b/tests/__ts-jest-mocks__/path.ts
@@ -3,7 +3,9 @@ import { } from 'node';
 
 interface MockedPath {
   __setBaseDir(newBaseDir);
-  resolve(args);
+  resolve(...args);
+  dirname(...args);
+  join(...args);
 }
 
 const path = require.requireActual('path');
@@ -19,11 +21,13 @@ function __setBaseDir(newBaseDir) {
 
 // A custom version of `readdirSync` that reads from the special mocked out
 // file list set via __setMockFiles
-function resolve(args) {
-  return path.resolve(baseDir, args);
+function resolve(...args) {
+  return path.resolve(baseDir, ...args);
 }
 
 mockedPath.__setBaseDir = __setBaseDir;
 mockedPath.resolve = resolve;
+mockedPath.dirname = path.dirname;
+mockedPath.join = path.join;
 
-module.exports = mockedPath;
\ No newline at end of file
+module.exports = mockedPath;
diff --git a/tests/tsconfig-test/extends-tsconfig.json b/tests/tsconfig-test/extends-tsconfig.json
new file mode 100644
index 0000000000..d0251e982d
--- /dev/null
+++ b/tests/tsconfig-test/extends-tsconfig.json
@@ -0,0 +1,3 @@
+{
+  "extends": "./my-tsconfig.json"
+}
diff --git a/tests/tsconfig-test/extends-with-overrides-tsconfig.json b/tests/tsconfig-test/extends-with-overrides-tsconfig.json
new file mode 100644
index 0000000000..8b6bfd641e
--- /dev/null
+++ b/tests/tsconfig-test/extends-with-overrides-tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "extends": "./my-tsconfig.json",
+  "compilerOptions": {
+    "target": "ES5",
+    "noImplicitAny": true
+  }
+}