refactor(ng-update): add links to migration guide in v9 hammer migration (#17769)

* Adds link to the migration guide in the v9 hammer migration
* Cleans up the gesture config to be less verbose, and to work with the default TSLint configuration in CLI projects

Author: devversion

src/material/schematics/ng-update/upgrade-rules/hammer-gestures-v9/gesture-config.template

@@ -1,61 +1,53 @@
 /**
  * Custom HammerJS configuration forked from Angular Material. With Angular v9,
  * Angular Material dropped HammerJS as a dependency. This configuration was added
- * automatically to this application because `ng update` detected that this application
- * directly used HammerJS.
+ * automatically to this application because ng-update detected that this application
+ * directly used custom HammerJS gestures defined by Angular Material.
  *
- * If this application does not depend on the custom gestures originally defined by
- * Angular Material, this file can be deleted.
+ * Read more in the dedicated guide: https://git.io/ng-material-v9-hammer-migration
  */
 
 import {Injectable, Inject, Optional, Type} from '@angular/core';
 import {HammerGestureConfig} from '@angular/platform-browser';
 import {MAT_HAMMER_OPTIONS} from '@angular/material/core';
 
-const SUPPORTED_CUSTOM_GESTURES = [
-  'longpress',
-  'slide',
-  'slidestart',
-  'slideend',
-  'slideright',
-  'slideleft'
-];
-
 /**
- * Fake HammerInstance that is used when a Hammer instance is requested when
- * HammerJS has not been loaded on the page.
+ * Noop hammer instance that is used when an instance is requested, but
+ * Hammer has not been loaded on the page yet.
  */
 const noopHammerInstance = {
   on: () => {},
   off: () => {},
 };
 
 /**
- * Adjusts configuration of our gesture library, Hammer.
- * @deprecated No longer being used. To be removed.
- * @breaking-change 10.0.0
+ * Gesture config that provides custom Hammer gestures on top of the default Hammer
+ * gestures. These gestures will be available as events in component templates.
  */
 @Injectable()
 export class GestureConfig extends HammerGestureConfig {
-  /** List of new event names to add to the gesture support list */
-  events = SUPPORTED_CUSTOM_GESTURES;
-
-  constructor(
-    @Optional() @Inject(MAT_HAMMER_OPTIONS) private _hammerOptions?: any) {
+  /** List of event names to add to the Hammer gesture plugin list */
+  events = [
+    'longpress',
+    'slide',
+    'slidestart',
+    'slideend',
+    'slideright',
+    'slideleft'
+  ];
+
+  constructor(@Optional() @Inject(MAT_HAMMER_OPTIONS) private hammerOptions?: any) {
     super();
   }
 
   /**
    * Builds Hammer instance manually to add custom recognizers that match the
-   * Material Design spec.
-   *
-   * Our gesture names come from the Material Design gestures spec:
-   * https://material.io/design/#gestures-touch-mechanics
-   *
-   * More information on default recognizers can be found in Hammer docs:
-   * http://hammerjs.github.io/recognizer-pan/
-   * http://hammerjs.github.io/recognizer-press/
+   * Material Design specification. Gesture names originate from the Material Design
+   * gestures: https://material.io/design/#gestures-touch-mechanics
    *
+   * More information on default recognizers can be found in the Hammer docs:
+   *   http://hammerjs.github.io/recognizer-pan/
+   *   http://hammerjs.github.io/recognizer-press/
    * @param element Element to which to assign the new HammerJS gestures.
    * @returns Newly-created HammerJS instance.
    */
@@ -66,7 +58,7 @@ export class GestureConfig extends HammerGestureConfig {
       return noopHammerInstance;
     }
 
-    const mc = new hammer(element, this._hammerOptions || undefined);
+    const mc = new hammer(element, this.hammerOptions || undefined);
 
     // Default Hammer Recognizers.
     const pan = new hammer.Pan();
@@ -95,11 +87,10 @@ export class GestureConfig extends HammerGestureConfig {
   }
 
   /** Creates a new recognizer, without affecting the default recognizers of HammerJS */
-  private _createRecognizer(base: Object, options: any, ...inheritances: Object[]) {
+  private _createRecognizer(base: object, options: any, ...inheritances: object[]) {
     const recognizer = new (base.constructor as Type<any>)(options);
     inheritances.push(base);
     inheritances.forEach(item => recognizer.recognizeWith(item));
     return recognizer;
   }
-
 }

src/material/schematics/ng-update/upgrade-rules/hammer-gestures-v9/hammer-gestures-rule.ts

@@ -178,7 +178,8 @@ export class HammerGesturesRule extends MigrationRule<null> {
             'The HammerJS v9 migration for Angular Components detected that HammerJS is ' +
             'manually set up in combination with references to the Angular Material gesture ' +
             'config. This target cannot be migrated completely, but all references to the ' +
-            'deprecated Angular Material gesture have been removed.');
+            'deprecated Angular Material gesture have been removed. Read more here: ' +
+            'https://git.io/ng-material-v9-hammer-ambiguous-usage');
       } else if (usedInTemplate && this._gestureConfigReferences.length) {
         // Since there is a reference to the Angular Material gesture config, and we detected
         // usage of a gesture event that could be provided by Angular Material, we *cannot*
@@ -188,7 +189,8 @@ export class HammerGesturesRule extends MigrationRule<null> {
             'The HammerJS v9 migration for Angular Components detected that HammerJS is ' +
             'manually set up in combination with references to the Angular Material gesture ' +
             'config. This target cannot be migrated completely. Please manually remove ' +
-            'references to the deprecated Angular Material gesture config.');
+            'references to the deprecated Angular Material gesture config. Read more here: ' +
+            'https://git.io/ng-material-v9-hammer-ambiguous-usage');
       }
     } else if (this._usedInRuntime || usedInTemplate) {
       // We keep track of whether Hammer is used globally. This is necessary because we
@@ -228,7 +230,8 @@ export class HammerGesturesRule extends MigrationRule<null> {
       this.printInfo(
           'The HammerJS v9 migration for Angular Components migrated the ' +
           'project to keep HammerJS installed, but detected ambiguous usage of HammerJS. Please ' +
-          'manually check if you can remove HammerJS from your application.');
+          'manually check if you can remove HammerJS from your application. More details: ' +
+          'https://git.io/ng-material-v9-hammer-ambiguous-usage');
     }
   }
 
@@ -852,6 +855,8 @@ export class HammerGesturesRule extends MigrationRule<null> {
         '\n⚠  General notice: The HammerJS v9 migration for Angular Components is not able to ' +
         'migrate tests. Please manually clean up tests in your project if they rely on ' +
         (this.globalUsesHammer ? 'the deprecated Angular Material gesture config.' : 'HammerJS.')));
+    context.logger.info(
+        'Read more about migrating tests: https://git.io/ng-material-v9-hammer-migrate-tests');
 
     if (!this.globalUsesHammer && this._removeHammerFromPackageJson(tree)) {
       // Since Hammer has been removed from the workspace "package.json" file,