fix(@schematics/angular): default interface for guard

Currently, if the user hits `<Enter>` before selecting an interface to implement, the CLI generates a broken guard that implements no interface. With this commit, the CLI forces a choice in interactive mode and generates a `CanActivate` guard by default.

Author: cexbrayat

packages/schematics/angular/guard/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicsException,
   Tree,
   apply,
   applyTemplates,
@@ -22,7 +21,7 @@ import {
 import { applyLintFix } from '../utility/lint-fix';
 import { parseName } from '../utility/parse-name';
 import { createDefaultPath } from '../utility/workspace';
-import { Schema as GuardOptions } from './schema';
+import { Implement as GuardInterface, Schema as GuardOptions } from './schema';
 
 
 export default function (options: GuardOptions): Rule {
@@ -37,13 +36,14 @@ export default function (options: GuardOptions): Rule {
 
     let implementations = '';
     let implementationImports = '';
-    if (options.implements.length > 0) {
-      implementations = options.implements.join(', ');
-      implementationImports = `${implementations}, `;
-      // As long as we aren't in IE... ;)
-      if (options.implements.includes('CanLoad')) {
-        implementationImports = `${implementationImports}Route, UrlSegment, `;
-      }
+    if (options.implements.length === 0) {
+      options.implements.push(GuardInterface.CanActivate);
+    }
+    implementations = options.implements.join(', ');
+    implementationImports = `${implementations}, `;
+    // As long as we aren't in IE... ;)
+    if (options.implements.includes(GuardInterface.CanLoad)) {
+      implementationImports = `${implementationImports}Route, UrlSegment, `;
     }
 
     const parsedPath = parseName(options.path, options.name);

packages/schematics/angular/guard/index_spec.ts

@@ -105,4 +105,17 @@ describe('Guard Schematic', () => {
       expect(fileString).toContain(functionName);
     });
   });
+
+  it('should use CanActivate if no implements value', async () => {
+    const options = { ...defaultOptions, implements: []};
+    const tree = await schematicRunner.runSchematicAsync('guard', options, appTree)
+      .toPromise();
+    const fileString = tree.readContent('/projects/bar/src/app/foo.guard.ts');
+    expect(fileString).toContain('CanActivate');
+    expect(fileString).toContain('canActivate');
+    expect(fileString).not.toContain('CanActivateChild');
+    expect(fileString).not.toContain('canActivateChild');
+    expect(fileString).not.toContain('CanLoad');
+    expect(fileString).not.toContain('canLoad');
+  });
 });

packages/schematics/angular/guard/schema.json

@@ -55,8 +55,16 @@
       "description": "Specifies which interfaces to implement.",
       "uniqueItems": true,
       "items": {
-        "type": "string"
+        "enum": [
+          "CanActivate",
+          "CanActivateChild",
+          "CanLoad"
+        ]
       },
+      "default": [
+        "CanActivate"
+      ],
+      "minItems": 1,
       "x-prompt": {
         "message": "Which interfaces would you like to implement?",
         "type": "list",