test Typescript type declaration

To run the test without those slow test: `npx ava --match ‘!*[slow]’`.

package.json

@@ -59,6 +59,7 @@
 		"codecov": "^3.0.0",
 		"delay": "^2.0.0",
 		"nyc": "^11.3.0",
+		"pkg-dir": "^2.0.0",
 		"typescript": "^2.6.2",
 		"xo": "*"
 	},

test/fixtures/compiles/emit.ts

@@ -0,0 +1,6 @@
+import Emittery  = require('../../..');
+
+const ee = new Emittery();
+
+ee.emit('anEvent');
+ee.emit('anEvent', 'some data');

test/fixtures/compiles/off.ts

@@ -0,0 +1,10 @@
+import Emittery = require('../../..');
+
+const ee = new Emittery();
+const listener = () => undefined;
+
+ee.off('anEvent', () => undefined);
+ee.off('anEvent', () => Promise.resolve());
+
+ee.off('anEvent', data => undefined);
+ee.off('anEvent', data => Promise.resolve());

test/fixtures/compiles/on.ts

@@ -0,0 +1,13 @@
+import Emittery = require('../../..');
+
+const ee = new Emittery();
+
+ee.on('anEvent', () => undefined);
+ee.on('anEvent', () => Promise.resolve());
+
+ee.on('anEvent', data => undefined);
+ee.on('anEvent', data => Promise.resolve());
+
+const off = ee.on('anEvent', () => undefined);
+
+off();

test/fixtures/compiles/tsconfig.json

@@ -0,0 +1,11 @@
+{
+	"compilerOptions": {
+		"target": "es2017",
+		"lib": ["es2017"],
+		"module": "commonjs",
+		"strict": true,
+		"moduleResolution": "node",
+		"allowSyntheticDefaultImports": true
+	},
+	"include": ["*.ts"]
+}

test/fixtures/fails/emit-extra.ts

@@ -0,0 +1,6 @@
+import Emittery  = require('../../..');
+
+const ee = new Emittery();
+
+ee.emit('anEvent');
+ee.emit('anEvent', 'some data', 'and more');

test/fixtures/fails/on-extra.ts

@@ -0,0 +1,6 @@
+import Emittery = require('../../..');
+
+const ee = new Emittery();
+
+ee.on('anEvent', (data, more) => undefined);
+

test/fixtures/tsconfig.json

@@ -0,0 +1,11 @@
+{
+	"compilerOptions": {
+		"target": "es2017",
+		"lib": ["es2017"],
+		"module": "commonjs",
+		"strict": true,
+		"moduleResolution": "node",
+		"allowSyntheticDefaultImports": true
+	},
+	"include": ["*.ts"]
+}

test/snapshots/types.js.md

@@ -0,0 +1,32 @@
+# Snapshot report for `test/types.js`
+
+The actual snapshot is saved in `types.js.snap`.
+
+Generated by [AVA](https://ava.li).
+
+## Type definition disallows invalid Emittery method calls to compile
+
+> Snapshot 1
+
+    `test/fixtures/fails/emit-extra.ts (6,1): Expected 1-2 arguments, but got 3.␊
+    test/fixtures/fails/on-extra.ts (5,18): Argument of type '(data: any, more: any) => undefined' is not assignable to parameter of type '() => any'.␊
+    test/fixtures/fails/on-extra.ts (5,19): Parameter 'data' implicitly has an 'any' type.␊
+    test/fixtures/fails/on-extra.ts (5,25): Parameter 'more' implicitly has an 'any' type.
+
+## Type definition disallows invalid Emittery method calls to compile [slow]
+
+> Snapshot 1
+
+    `test/fixtures/fails/emit-extra.ts (6,1): Expected 1-2 arguments, but got 3.␊
+    test/fixtures/fails/on-extra.ts (5,18): Argument of type '(data: any, more: any) => undefined' is not assignable to parameter of type '() => any'.␊
+    test/fixtures/fails/on-extra.ts (5,19): Parameter 'data' implicitly has an 'any' type.␊
+    test/fixtures/fails/on-extra.ts (5,25): Parameter 'more' implicitly has an 'any' type.
+
+## TS warns about invalid Emittery method calls [slow]
+
+> Snapshot 1
+
+    `test/fixtures/fails/emit-extra.ts (6,1): Expected 1-2 arguments, but got 3.␊
+    test/fixtures/fails/on-extra.ts (5,18): Argument of type '(data: any, more: any) => undefined' is not assignable to parameter of type '(eventData?: any) => any'.␊
+    test/fixtures/fails/on-extra.ts (5,19): Parameter 'data' implicitly has an 'any' type.␊
+    test/fixtures/fails/on-extra.ts (5,25): Parameter 'more' implicitly has an 'any' type.`

test/types.js

@@ -0,0 +1,79 @@
+import {readdirSync, statSync} from 'fs';
+import {resolve as _resolve, join, extname, relative} from 'path';
+import pkgUp from 'pkg-dir';
+
+import test from 'ava';
+import * as ts from 'typescript';
+
+const resolve = _resolve.bind(null, __dirname);
+const validExtension = new Set(['.js', '.ts']);
+const compilerOptions = {
+	target: ts.ScriptTarget.ES2017,
+	module: ts.ModuleKind.CommonJS,
+	strict: true,
+	noEmit: true
+};
+
+test('TS can compile valid Emittery method calls [slow]', assertAllCompile, './fixtures/compiles');
+test('TS warns about invalid Emittery method calls [slow]', assertEachFail, './fixtures/fails');
+
+function assertAllCompile(t, srcDir) {
+	const fileNames = listFiles(resolve(srcDir));
+	const errors = compile(fileNames);
+
+	t.is(errors.length, 0, errorMessage(errors));
+}
+
+function assertEachFail(t, srcDir) {
+	const fileNames = listFiles(resolve(srcDir)).sort();
+	const errors = compile(fileNames);
+	const filesWithErrors = errors
+		.map(err => (err.file ? err.file.fileName : null))
+		.filter(Boolean)
+		.filter(unique);
+
+	t.deepEqual(filesWithErrors, fileNames, 'Some file did not emit any compile error.');
+	t.snapshot(errorMessage(errors));
+}
+
+function listFiles(srcRoot) {
+	return readdirSync(srcRoot)
+		.filter(hasValidExtension)
+		.map(name => join(srcRoot, name))
+		.filter(isFile);
+}
+
+function compile(fileNames, options = compilerOptions) {
+	const program = ts.createProgram(fileNames, options);
+	const emitResult = program.emit();
+
+	return ts.getPreEmitDiagnostics(program).concat(emitResult.diagnostics);
+}
+
+function errorMessage(diagnosticList) {
+	const root = pkgUp.sync();
+
+	return diagnosticList.map(diagnostic => {
+		if (!diagnostic.file) {
+			return `${ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n')}`;
+		}
+
+		const {line, character} = diagnostic.file.getLineAndCharacterOfPosition(diagnostic.start);
+		const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n');
+		const fileName = relative(root, diagnostic.file.fileName);
+
+		return `${fileName} (${line + 1},${character + 1}): ${message}`;
+	}).join('\n');
+}
+
+function isFile(path) {
+	return statSync(path).isFile();
+}
+
+function hasValidExtension(path) {
+	return validExtension.has(extname(path));
+}
+
+function unique(value, index, list) {
+	return list.indexOf(value) === index;
+}

tsconfig.json

@@ -8,5 +8,6 @@
 		"allowSyntheticDefaultImports": true,
 		"allowJs": true
 	},
-	"include": ["**/*.ts"]
+	"include": ["**/*"],
+	"exclude": ["test/fixtures/**/*"]
 }