From f6a902f8ce35e613908ecc06c6809ff2f28d45aa Mon Sep 17 00:00:00 2001
From: Oscar Busk <oscar.busk@gmail.com>
Date: Thu, 28 Jun 2018 12:27:49 +0200
Subject: [PATCH] Improve module.filter() by allowing `$stateful` to be
 defined.

---
 types/angular/angular-tests.ts | 15 +++++++++++----
 types/angular/index.d.ts       | 13 +++++++++++--
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/types/angular/angular-tests.ts b/types/angular/angular-tests.ts
index 1dff1a0451..3e67c88e67 100644
--- a/types/angular/angular-tests.ts
+++ b/types/angular/angular-tests.ts
@@ -214,11 +214,18 @@ mod.factory({
     name1(foo: any) {},
     name2: ['foo', (foo: any) => {}]
 });
-mod.filter('name', ($scope: ng.IScope) => {});
-mod.filter('name', ['$scope', ($scope: ng.IScope) => {}]);
+mod.filter('name', ($scope: ng.IScope) => () => {});
+mod.filter('name', ['$scope', ($scope: ng.IScope) => () => {}]);
 mod.filter({
-    name1(foo: any) {},
-    name2: ['foo', (foo: any) => {}]
+    name1(foo: any) { return () => {}; },
+    name2: ['foo', (foo: any) => () => {}],
+});
+const customStatefulFilter: ng.FilterFunction<(s: string) => number> = (s) => 1;
+mod.filter('name', () => customStatefulFilter);
+mod.filter('name', ['$scope', () => customStatefulFilter]);
+mod.filter({
+    name1: () => customStatefulFilter,
+    name2: ['foo', () => customStatefulFilter],
 });
 mod.provider('name', ($scope: ng.IScope) => ({ $get: () => { } }));
 mod.provider('name', TestProvider);
diff --git a/types/angular/index.d.ts b/types/angular/index.d.ts
index 6b82a2bcb4..50d28a2dbb 100644
--- a/types/angular/index.d.ts
+++ b/types/angular/index.d.ts
@@ -250,8 +250,8 @@ declare namespace angular {
          */
         factory(name: string, $getFn: Injectable<Function>): IModule;
         factory(object: {[name: string]: Injectable<Function>}): IModule;
-        filter(name: string, filterFactoryFunction: Injectable<Function>): IModule;
-        filter(object: {[name: string]: Injectable<Function>}): IModule;
+        filter(name: string, filterFactoryFunction: Injectable<FilterFactory<Function>>): IModule;
+        filter(object: {[name: string]: Injectable<FilterFactory<Function>>}): IModule;
         provider(name: string, serviceProviderFactory: IServiceProviderFactory): IModule;
         provider(name: string, serviceProviderConstructor: IServiceProviderClass): IModule;
         provider(name: string, inlineAnnotatedConstructor: any[]): IModule;
@@ -2237,4 +2237,13 @@ declare namespace angular {
     interface IHttpParamSerializer {
         (obj: Object): string;
     }
+
+    type FilterFunction<Filter extends Function> = {
+        /**
+         * By default, filters are only run once the input value changes. By marking the filter as `$stateful`, the filter will be run on every `$digest` to update the output. **This is strongly discouraged.**
+         * See https://docs.angularjs.org/guide/filter#stateful-filters
+         */
+        $stateful?: boolean
+    } & Filter;
+    type FilterFactory<Filter extends Function> = (...I: any[]) => FilterFunction<Filter>;
 }