Add TypeScript definition (#12)

index.d.ts

@@ -0,0 +1,67 @@
+import * as typeFest from 'type-fest';
+import normalize = require('normalize-package-data');
+
+declare namespace readPkg {
+	interface Options {
+		/**
+		[Normalize](https://github.com/npm/normalize-package-data#what-normalization-currently-entails) the package data.
+
+		@default true
+		*/
+		normalize?: boolean;
+
+		/**
+		Current working directory.
+
+		@default process.cwd()
+		*/
+		cwd?: string;
+	}
+
+	interface NormalizeOptions extends Options {
+		normalize: true;
+	}
+
+	type NormalizedPackageJson = PackageJson & normalize.Package;
+	type PackageJson = typeFest.PackageJson;
+}
+
+declare const readPkg: {
+	/**
+	@returns The parsed JSON.
+
+	@example
+	```
+	import readPkg = require('read-pkg');
+
+	(async () => {
+		console.log(await readPkg());
+		//=> {name: 'read-pkg', …}
+
+		console.log(await readPkg({cwd: 'some-other-directory'});
+		//=> {name: 'unicorn', …}
+	})();
+	```
+	*/
+	(options?: readPkg.NormalizeOptions): Promise<readPkg.NormalizedPackageJson>;
+	(options: readPkg.Options): Promise<readPkg.PackageJson>;
+
+	/**
+	@returns The parsed JSON.
+
+	@example
+	```
+	import readPkg = require('read-pkg');
+
+	console.log(readPkg.sync());
+	//=> {name: 'read-pkg', …}
+
+	console.log(readPkg.sync({cwd: 'some-other-directory'});
+	//=> {name: 'unicorn', …}
+	```
+	*/
+	sync(options?: readPkg.NormalizeOptions): readPkg.NormalizedPackageJson;
+	sync(options: readPkg.Options): readPkg.PackageJson;
+};
+
+export = readPkg;

index.test-d.ts

@@ -0,0 +1,20 @@
+import {expectType, expectError} from 'tsd';
+import readPkg = require('.');
+
+const options: readPkg.Options = {};
+expectError<readPkg.NormalizedPackageJson>({});
+expectType<readPkg.PackageJson>({});
+
+expectType<Promise<readPkg.NormalizedPackageJson>>(readPkg());
+expectType<Promise<readPkg.NormalizedPackageJson>>(readPkg({normalize: true}));
+expectType<Promise<readPkg.PackageJson>>(readPkg({normalize: false}));
+expectError<Promise<readPkg.NormalizedPackageJson>>(
+	readPkg({normalize: false})
+);
+expectType<Promise<readPkg.PackageJson>>(readPkg({cwd: './'}));
+
+expectType<readPkg.NormalizedPackageJson>(readPkg.sync());
+expectType<readPkg.NormalizedPackageJson>(readPkg.sync({normalize: true}));
+expectType<readPkg.PackageJson>(readPkg.sync({normalize: false}));
+expectError<readPkg.NormalizedPackageJson>(readPkg.sync({normalize: false}));
+expectType<readPkg.PackageJson>(readPkg.sync({cwd: './'}));

package.json

@@ -13,10 +13,11 @@
 		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"json",
@@ -31,11 +32,14 @@
 		"normalize"
 	],
 	"dependencies": {
-		"normalize-package-data": "^2.3.2",
-		"parse-json": "^4.0.0"
+		"@types/normalize-package-data": "^2.4.0",
+		"normalize-package-data": "^2.5.0",
+		"parse-json": "^4.0.0",
+		"type-fest": "^0.4.1"
 	},
 	"devDependencies": {
-		"ava": "^1.3.1",
+		"ava": "^1.4.1",
+		"tsd": "^0.7.2",
 		"xo": "^0.24.0"
 	},
 	"xo": {

readme.md

@@ -36,15 +36,15 @@ const readPkg = require('read-pkg');
 
 ### readPkg([options])
 
-Returns a `Promise` for the parsed JSON.
+Returns a `Promise<object>` with the parsed JSON.
 
 ### readPkg.sync([options])
 
 Returns the parsed JSON.
 
 #### options
 
-Type: `Object`
+Type: `object`
 
 ##### cwd