From 10a1e1974b816ebb979dc10586b160ee07ad8356 Mon Sep 17 00:00:00 2001
From: Paul Gschwendtner <paulgschwendtner@gmail.com>
Date: Fri, 14 Jun 2019 13:12:34 +0200
Subject: [PATCH] fix(platform-browser): debug element query predicates not
 compatible with strictFunctionTypes (#30993)

Currently developers can use the `By` class to construct common
`DebugElement` query predicates. e.g. `By.directive(MyDirective)`.

The `directive()` and `all()` predicates are currently returning
a predicate that works for `DebugElement` nodes. This return type
is too strict since the predicate is not specific to `DebugElement`
instances and can also apply to `DebugNode` instances.

Meaning that developers are currently able to use the `directive()`
predicate when using `queryAllNodes()`. This is a common practice
but will break when the project is compiled with TypeScript's
`--strictFunctionTypes` flag as the `DebugElement` predicate type
is not assignable to predicates for `DebugNode`. In order to make
these predicates usable with `--strictFuntionTypes` enabled, we
adjust the predicate type to reflect what is actually needed for
evaluation of the predicate.

PR Close #30993
---
 packages/platform-browser/src/dom/debug/by.ts        | 12 ++++++------
 .../platform-browser/platform-browser.d.ts           |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/packages/platform-browser/src/dom/debug/by.ts b/packages/platform-browser/src/dom/debug/by.ts
index b8941f604c..2d7006b16f 100644
--- a/packages/platform-browser/src/dom/debug/by.ts
+++ b/packages/platform-browser/src/dom/debug/by.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {DebugElement, Predicate, Type} from '@angular/core';
+import {DebugElement, DebugNode, Predicate, Type} from '@angular/core';
 import {getDOM} from '../../dom/dom_adapter';
 
 
@@ -18,14 +18,14 @@ import {getDOM} from '../../dom/dom_adapter';
  */
 export class By {
   /**
-   * Match all elements.
+   * Match all nodes.
    *
    * @usageNotes
    * ### Example
    *
    * {@example platform-browser/dom/debug/ts/by/by.ts region='by_all'}
    */
-  static all(): Predicate<DebugElement> { return (debugElement) => true; }
+  static all(): Predicate<DebugNode> { return () => true; }
 
   /**
    * Match elements by the given CSS selector.
@@ -44,14 +44,14 @@ export class By {
   }
 
   /**
-   * Match elements that have the given directive present.
+   * Match nodes that have the given directive present.
    *
    * @usageNotes
    * ### Example
    *
    * {@example platform-browser/dom/debug/ts/by/by.ts region='by_directive'}
    */
-  static directive(type: Type<any>): Predicate<DebugElement> {
-    return (debugElement) => debugElement.providerTokens !.indexOf(type) !== -1;
+  static directive(type: Type<any>): Predicate<DebugNode> {
+    return (debugNode) => debugNode.providerTokens !.indexOf(type) !== -1;
   }
 }
diff --git a/tools/public_api_guard/platform-browser/platform-browser.d.ts b/tools/public_api_guard/platform-browser/platform-browser.d.ts
index e6a3d02824..1d380def79 100644
--- a/tools/public_api_guard/platform-browser/platform-browser.d.ts
+++ b/tools/public_api_guard/platform-browser/platform-browser.d.ts
@@ -9,9 +9,9 @@ export declare class BrowserTransferStateModule {
 }
 
 export declare class By {
-    static all(): Predicate<DebugElement>;
+    static all(): Predicate<DebugNode>;
     static css(selector: string): Predicate<DebugElement>;
-    static directive(type: Type<any>): Predicate<DebugElement>;
+    static directive(type: Type<any>): Predicate<DebugNode>;
 }
 
 export declare function disableDebugTools(): void;