compression-webpack-plugin: Support custom algorithm

Had to bump the TypeScript version to detect correct option type based on `algorithm` argument.

types/compression-webpack-plugin/compression-webpack-plugin-tests.ts

@@ -1,7 +1,9 @@
 import { Configuration } from 'webpack';
 import CompressionPlugin = require('compression-webpack-plugin');
 
-const c: Configuration = {
+new CompressionPlugin();
+
+const config: Configuration = {
     plugins: [
         new CompressionPlugin({
             asset: "[path].gz[query]",
@@ -13,3 +15,52 @@ const c: Configuration = {
         })
     ]
 };
+
+const configDefaultAlgo = new CompressionPlugin({
+    compressionOptions: { level: 7 }
+});
+
+const zlib: Configuration = {
+    plugins: [
+        new CompressionPlugin({
+            algorithm: "deflate",
+            compressionOptions: {
+                flush: 5,
+                windowBits: 20,
+                level: 7
+            }
+        })
+    ]
+};
+
+const badZlib: Configuration = {
+    plugins: [
+        // $ExpectError
+        new CompressionPlugin({
+            algorithm: "deflate",
+            compressionOptions: 5
+        })
+    ]
+};
+
+function customAlgorithm(input: string, options: number, callback: (err: Error, result: Buffer) => void) {
+}
+
+const custom: Configuration = {
+    plugins: [
+        new CompressionPlugin({
+            algorithm: customAlgorithm,
+            compressionOptions: 5
+        })
+    ]
+};
+
+const badCustom: Configuration = {
+    plugins: [
+        // $ExpectError
+        new CompressionPlugin({
+            algorithm: customAlgorithm,
+            compressionOptions: { flush: 5 }
+        })
+    ]
+};

types/compression-webpack-plugin/index.d.ts

@@ -2,33 +2,42 @@
 // Project: https://github.com/webpack-contrib/compression-webpack-plugin
 // Definitions by: Anton Kandybo <https://github.com/dublicator>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
-// TypeScript Version: 2.3
+// TypeScript Version: 2.4
 
 import { Plugin } from 'webpack';
+import { ZlibOptions as ZlibCompressionOptions } from 'zlib';
 
 export = CompressionPlugin;
 
-declare class CompressionPlugin extends Plugin {
-    constructor(options?: CompressionPlugin.Options);
+declare class CompressionPlugin<O = any> extends Plugin {
+    constructor(options?: CompressionPlugin.Options<O>);
 }
 
 declare namespace CompressionPlugin {
-    interface Options {
+    type AlgorithmCallback = (error: Error | null, result: Buffer) => void;
+    type Algorithm<O> = (source: string, options: O, callback: AlgorithmCallback) => void;
+
+    // NOTE: These are the compression algorithms exported by zlib.
+    type ZlibAlgorithm = 'deflate' | 'deflateRaw' | 'gzip';
+
+    interface BaseOptions {
         asset?: string;
-        algorithm?: string;
         cache?: boolean | string;
         test?: RegExp | RegExp[];
         regExp?: RegExp | RegExp[];
         threshold?: number;
         minRatio?: number;
-
-        // zlib options
-        level?: number;
-        flush?: number;
-        chunkSize?: number;
-        windowBits?: number;
-        memLevel?: number;
-        strategy?: number;
-        dictionary?: any;
     }
+
+    interface ZlibOptions extends BaseOptions {
+        algorithm?: ZlibAlgorithm;
+        compressionOptions?: ZlibCompressionOptions;
+    }
+
+    interface CustomOptions<O> extends BaseOptions {
+        algorithm: Algorithm<O>;
+        compressionOptions?: O;
+    }
+
+    type Options<O> = ZlibOptions | CustomOptions<O>;
 }