Correctly merge default compiler options

readme.md

@@ -91,6 +91,35 @@ When you have spread your tests over multiple files, you can store all those fil
 
 Now you can put all your test files in the `my-test-dir` directory.
 
+### Custom TypeScript config
+
+By default, `tsd-check` applies the following configuration:
+
+```json5
+{
+	"strict": true,
+	"jsx": "react",
+	"target": "es2017",
+	// The following options are set and are not overridable:
+	"moduleResolution": "node",
+	"skipLibCheck": true
+}
+```
+
+If you wish to override these options, you have the possibility to provide a custom TypeScript config to `tsd-check` by specifying it in `package.json`.
+
+*Default options will still apply if you don't override them explicitly.* You can't override the `moduleResolution` and `skipLibCheck` options.
+
+```json
+{
+	"name": "my-module",
+	"tsd-check": {
+		"compilerOptions": {
+			"strict": false
+		}
+	}
+}
+```
 
 ## Assertions
 

source/lib/config.ts

@@ -7,21 +7,17 @@ import {Config} from './interfaces';
  * @param pkg - The package.json object.
  * @returns The config object.
  */
-export default (pkg: any): Config => {
-	const config = {
+export default (pkg: {'tsd-check'?: Partial<Config>}): Config => {
+	const pkgConfig = pkg['tsd-check'] || {};
+
+	return {
 		directory: 'test-d',
+		...pkgConfig,
 		compilerOptions: {
 			strict: true,
 			jsx: JsxEmit.React,
-			target: ScriptTarget.ES2017
-		},
-		...pkg['tsd-check']
-	};
-
-	return {
-		...config,
-		compilerOptions: {
-			...config.compilerOptions,
+			target: ScriptTarget.ES2017,
+			...pkgConfig.compilerOptions,
 			...{
 				moduleResolution: ModuleResolutionKind.NodeJs,
 				skipLibCheck: true

source/test/fixtures/strict-null-checks-as-default-config-value/index.d.ts

@@ -0,0 +1 @@
+export default function (foo: number): number | null;

source/test/fixtures/strict-null-checks-as-default-config-value/index.js

@@ -0,0 +1,3 @@
+module.exports.default = foo => {
+	return foo > 0 ? foo : null;
+};

source/test/fixtures/strict-null-checks-as-default-config-value/index.test-d.ts

@@ -0,0 +1,4 @@
+import {expectType} from '../../..';
+import aboveZero from '.';
+
+expectType<number>(aboveZero(1));

source/test/fixtures/strict-null-checks-as-default-config-value/package.json

@@ -0,0 +1,7 @@
+{
+	"name": "foo",
+	"tsd-check": {
+		"compilerOptions": {
+		}
+	}
+}

source/test/test.ts

@@ -64,9 +64,22 @@ test('fail if tests don\'t pass in strict mode', async t => {
 
 	const {fileName, message, severity, line, column} = diagnostics[0];
 	t.true(/failure-strict-null-checks\/index.test-d.ts$/.test(fileName));
-	t.is(
-		message,
-		`Argument of type 'number | null' is not assignable to parameter of type 'number'.
+	t.is(message, `Argument of type 'number | null' is not assignable to parameter of type 'number'.
+  Type \'null\' is not assignable to type 'number'.`
+	);
+	t.is(severity, 'error');
+	t.is(line, 4);
+	t.is(column, 19);
+});
+
+test('overridden config defaults to `strict` if `strict` is not explicitly overridden', async t => {
+	const diagnostics = await m({
+		cwd: path.join(__dirname, 'fixtures/strict-null-checks-as-default-config-value')
+	});
+
+	const {fileName, message, severity, line, column} = diagnostics[0];
+	t.true(/strict-null-checks-as-default-config-value\/index.test-d.ts$/.test(fileName));
+	t.is(message, `Argument of type 'number | null' is not assignable to parameter of type 'number'.
   Type \'null\' is not assignable to type 'number'.`
 	);
 	t.is(severity, 'error');