feat(@angular/cli): Added support for multiselect list prompt (#13031)

* feat(@angular/cli): Added support for multiselect list prompt

* If multiselect option is true use the checkbox
   inquirer prompt type, otherwise use list.

* feat(@angular-devkit/core): Added support for multiselect list prompt

* Added multiselect to PromptDefinition interface and usages

packages/angular/cli/models/schematic-command.ts

@@ -309,7 +309,7 @@ export abstract class SchematicCommand<
               question.type = 'confirm';
               break;
             case 'list':
-              question.type = 'list';
+              question.type = !!definition.multiselect ? 'checkbox' : 'list';
               question.choices = definition.items && definition.items.map(item => {
                 if (typeof item == 'string') {
                   return item;

packages/angular_devkit/core/src/json/schema/interface.ts

@@ -99,13 +99,14 @@ export interface PromptDefinition {
   id: string;
   type: string;
   message: string;
-  default?: string | number | boolean | null;
+  default?: string | string[] | number | boolean | null;
   priority: number;
   validator?: (value: string) => boolean | string | Promise<boolean | string>;
 
   items?: Array<string | { value: JsonValue, label: string }>;
 
   raw?: string | JsonObject;
+  multiselect?: boolean;
 }
 
 export type PromptProvider = (definitions: Array<PromptDefinition>)

packages/angular_devkit/core/src/json/schema/prompt_spec.ts

@@ -262,6 +262,83 @@ describe('Prompt Provider', () => {
         .toPromise().then(done, done.fail);
     });
 
+    it('analyzes list with multiselect option and object items', done => {
+      const registry = new CoreSchemaRegistry();
+      const data: any = {};
+
+      registry.usePromptProvider(async definitions => {
+        expect(definitions.length).toBe(1);
+        expect(definitions[0].type).toBe('list');
+        expect(definitions[0].multiselect).toBe(true);
+        expect(definitions[0].items).toEqual([
+          { 'value': 'one', 'label': 'one' },
+          { 'value': 'two', 'label': 'two' },
+        ]);
+
+        return { [definitions[0].id]: { 'value': 'one', 'label': 'one' } };
+      });
+
+      registry
+        .compile({
+          properties: {
+            test: {
+              type: 'array',
+              'x-prompt': {
+                'type': 'list',
+                'multiselect': true,
+                'items': [
+                  { 'value': 'one', 'label': 'one' },
+                  { 'value': 'two', 'label': 'two' },
+                ],
+                'message': 'test-message',
+              },
+            },
+          },
+        })
+        .pipe(
+          mergeMap(validator => validator(data)),
+        )
+        .toPromise().then(done, done.fail);
+    });
+
+    it('analyzes list without multiselect option and object items', done => {
+      const registry = new CoreSchemaRegistry();
+      const data: any = {};
+
+      registry.usePromptProvider(async definitions => {
+        expect(definitions.length).toBe(1);
+        expect(definitions[0].type).toBe('list');
+        expect(definitions[0].multiselect).toBeUndefined();
+        expect(definitions[0].items).toEqual([
+          { 'value': 'one', 'label': 'one' },
+          { 'value': 'two', 'label': 'two' },
+        ]);
+
+        return { [definitions[0].id]: { 'value': 'two', 'label': 'two' } };
+      });
+
+      registry
+        .compile({
+          properties: {
+            test: {
+              type: 'array',
+              'x-prompt': {
+                'type': 'list',
+                'items': [
+                  { 'value': 'one', 'label': 'one' },
+                  { 'value': 'two', 'label': 'two' },
+                ],
+                'message': 'test-message',
+              },
+            },
+          },
+        })
+        .pipe(
+          mergeMap(validator => validator(data)),
+        )
+        .toPromise().then(done, done.fail);
+    });
+
     it('analyzes enums WITHOUT explicit list type', done => {
       const registry = new CoreSchemaRegistry();
       const data: any = {};

packages/angular_devkit/core/src/json/schema/registry.ts

@@ -568,6 +568,7 @@ export class CoreSchemaRegistry implements SchemaRegistry {
           priority: 0,
           raw: schema,
           items,
+          multiselect: type === 'list' ? schema.multiselect : false,
           default: typeof parentSchema.default == 'object' ? undefined : parentSchema.default,
           async validator(data: string) {
             const result = it.self.validate(parentSchema, data);

packages/angular_devkit/schematics_cli/bin/schematics.ts

@@ -98,7 +98,7 @@ function _createPromptProvider(): schema.PromptProvider {
         case 'list':
           return {
             ...question,
-            type: 'list',
+            type: !!definition.multiselect ? 'checkbox' : 'list',
             choices: definition.items && definition.items.map(item => {
               if (typeof item == 'string') {
                 return item;