fix(@angular/cli): resolve relative schematic from angular.json instead of current working directory

Relative schematics referenced in `angular.json` `schematicCollections` and `defaultCollection` were always resolved from the current working directory, which is not correct and caused the collection not to be resolved when the this is different from the location of the workspace config.

Closes angular#23136

Author: alan-agius4

packages/angular/cli/src/command-builder/schematics-command-module.ts

@@ -14,6 +14,7 @@ import {
   NodeWorkflow,
 } from '@angular-devkit/schematics/tools';
 import type { CheckboxQuestion, Question } from 'inquirer';
+import { resolve } from 'path';
 import { Argv } from 'yargs';
 import { getProjectByCwd, getSchematicDefaults } from '../utilities/config';
 import { memoize } from '../utilities/memoize';
@@ -232,6 +233,12 @@ export abstract class SchematicsCommandModule
 
   @memoize
   protected async getSchematicCollections(): Promise<Set<string>> {
+    // Resolve relative collections from the location of `angular.json`
+    const resolveRelativeCollection = (collectionName: string) =>
+      collectionName.charAt(0) === '.'
+        ? resolve(this.context.root, collectionName)
+        : collectionName;
+
     const getSchematicCollections = (
       configSection: Record<string, unknown> | undefined,
     ): Set<string> | undefined => {
@@ -241,9 +248,9 @@ export abstract class SchematicsCommandModule
 
       const { schematicCollections, defaultCollection } = configSection;
       if (Array.isArray(schematicCollections)) {
-        return new Set(schematicCollections);
+        return new Set(schematicCollections.map((c) => resolveRelativeCollection(c)));
       } else if (typeof defaultCollection === 'string') {
-        return new Set([defaultCollection]);
+        return new Set([resolveRelativeCollection(defaultCollection)]);
       }
 
       return undefined;