fix(@schematics/angular): Allow prefix to be an empty string

fixes angular/angular-cli#10659

Author: Brocco

packages/schematics/angular/component/index.ts

@@ -96,7 +96,7 @@ function buildSelector(options: ComponentOptions, projectPrefix: string) {
   let selector = strings.dasherize(options.name);
   if (options.prefix) {
     selector = `${options.prefix}-${selector}`;
-  } else if (projectPrefix) {
+  } else if (options.prefix === undefined && projectPrefix) {
     selector = `${projectPrefix}-${selector}`;
   }
 

packages/schematics/angular/component/index_spec.ts

@@ -205,6 +205,14 @@ describe('Component Schematic', () => {
     expect(content).toMatch(/selector: 'app-foo'/);
   });
 
+  it('should use the supplied prefix if it is ""', () => {
+    const options = { ...defaultOptions, prefix: '' };
+
+    const tree = schematicRunner.runSchematic('component', options, appTree);
+    const content = tree.readContent('/projects/bar/src/app/foo/foo.component.ts');
+    expect(content).toMatch(/selector: 'foo'/);
+  });
+
   it('should respect the inlineTemplate option', () => {
     const options = { ...defaultOptions, inlineTemplate: true };
     const tree = schematicRunner.runSchematic('component', options, appTree);

packages/schematics/angular/component/schema.json

@@ -52,9 +52,17 @@
     },
     "prefix": {
       "type": "string",
-      "format": "html-selector",
       "description": "The prefix to apply to generated selectors.",
-      "alias": "p"
+      "alias": "p",
+      "oneOf": [
+        {
+          "maxLength": 0
+        },
+        {
+          "minLength": 1,
+          "format": "html-selector"
+        }
+      ]
     },
     "styleext": {
       "description": "The file extension to be used for style files.",

packages/schematics/angular/directive/index.ts

@@ -94,7 +94,7 @@ function buildSelector(options: DirectiveOptions, projectPrefix: string) {
   let selector = options.name;
   if (options.prefix) {
     selector = `${options.prefix}-${selector}`;
-  } else if (projectPrefix) {
+  } else if (options.prefix === undefined && projectPrefix) {
     selector = `${projectPrefix}-${selector}`;
   }
 

packages/schematics/angular/directive/index_spec.ts

@@ -146,4 +146,12 @@ describe('Directive Schematic', () => {
     const content = tree.readContent('/projects/bar/src/app/foo.directive.ts');
     expect(content).toMatch(/selector: '\[appFoo\]'/);
   });
+
+  it('should use the supplied prefix if it is ""', () => {
+    const options = { ...defaultOptions, prefix: '' };
+    const tree = schematicRunner.runSchematic('directive', options, appTree);
+
+    const content = tree.readContent('/projects/bar/src/app/foo.directive.ts');
+    expect(content).toMatch(/selector: '\[foo\]'/);
+  });
 });

packages/schematics/angular/directive/schema.json

@@ -27,10 +27,17 @@
     },
     "prefix": {
       "type": "string",
-      "format": "html-selector",
       "description": "The prefix to apply to generated selectors.",
-      "default": "app",
-      "alias": "p"
+      "alias": "p",
+      "oneOf": [
+        {
+          "maxLength": 0
+        },
+        {
+          "minLength": 1,
+          "format": "html-selector"
+        }
+      ]
     },
     "spec": {
       "type": "boolean",