[@types/nunjucks] Fix types for functions in Environment (#40026)

* [@types/nunjucks] Fix function signiatures in Environment

* [@types/nunjucks] Add tests for improved Environment function signiatures

types/nunjucks/index.d.ts

@@ -1,6 +1,7 @@
 // Type definitions for nunjucks 3.1
 // Project: http://mozilla.github.io/nunjucks/, https://github.com/mozilla/nunjucks
 // Definitions by: Ruben Slabbert <https://github.com/RubenSlabbert>
+//                 Matthew Burstein <https://github.com/MatthewBurstein>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.2
 
@@ -74,15 +75,16 @@ export class Environment {
     renderString(name: string, context: object): string;
     renderString(name: string, context: object, callback?: TemplateCallback<string>): void;
 
-    addFilter(name: string, func: (...args: any[]) => any, async?: boolean): void;
-    getFilter(name: string): void;
+    addFilter(name: string, func: (...args: any[]) => any, async?: boolean): Environment;
+    getFilter(name: string): (...args: any[]) => any;
 
-    addExtension(name: string, ext: Extension): void;
+    addExtension(name: string, ext: Extension): Environment;
     removeExtension(name: string): void;
     getExtension(name: string): Extension;
-    hasExtension(name: string): void;
+    hasExtension(name: string): boolean;
 
-    addGlobal(name: string, value: any): void;
+    addGlobal(name: string, value: any): Environment;
+    getGlobal(name: string): any;
 
     getTemplate(name: string, eagerCompile?: boolean): Template;
     getTemplate(name: string, eagerCompile?: boolean, callback?: Callback<Error, Template>): void;

types/nunjucks/nunjucks-tests.ts

@@ -35,12 +35,22 @@ nunjucks.configure('views', {
 });
 rendered = env.renderString(src, ctx);
 
-env.addExtension("SpawnGlitter", {
-    tags: ["glitter", "star wars", "Age of Empires"],
-    parse(parser, nodes, lexer) {
-        return "The parser api is complicated";
-    }
-});
+let extension: nunjucks.Extension = {
+  tags: ["glitter", "star wars", "Age of Empires"],
+  parse(parser, nodes, lexer) {
+      return "The parser api is complicated";
+  }
+};
+env = env.addExtension("SpawnGlitter", extension);
+const hasExtension: boolean = env.hasExtension('SpawnGlitter');
+extension = env.getExtension('SpawnGlitter');
+env.removeExtension('SpawnGlitter');
+
+env = env.addGlobal('key', 'value');
+const value = env.getGlobal('key');
+
+env = env.addFilter('testFilter', arg => arg, false);
+const testFilter: ((arg: any) => any) = env.getFilter('testFilter');
 
 nunjucks.installJinjaCompat();