fix(material/schematics): error if stylesheet contains syntax errors

Fixes that the `mat.core` migration was breaking the whole update process if a stylesheet has syntax errors.

Fixes #30115.

(cherry picked from commit c891926)

src/material/schematics/ng-update/migrations/mat-core-removal.ts

@@ -25,16 +25,23 @@ export class MatCoreMigration extends Migration<UpgradeData, DevkitContext> {
   }
 
   override visitStylesheet(stylesheet: ResolvedResource): void {
-    const processor = new postcss.Processor([
-      {
-        postcssPlugin: 'mat-core-removal-v19-plugin',
-        AtRule: {
-          use: node => this._getNamespace(node),
-          include: node => this._handleAtInclude(node, stylesheet.filePath),
+    try {
+      const processor = new postcss.Processor([
+        {
+          postcssPlugin: 'mat-core-removal-v19-plugin',
+          AtRule: {
+            use: node => this._getNamespace(node),
+            include: node => this._handleAtInclude(node, stylesheet.filePath),
+          },
         },
-      },
-    ]);
-    processor.process(stylesheet.content, {syntax: scss}).sync();
+      ]);
+      processor.process(stylesheet.content, {syntax: scss}).sync();
+    } catch (e) {
+      this.logger.warn(
+        `Failed to migrate usages of mat.core in ${stylesheet.filePath} due to error:`,
+      );
+      this.logger.warn(e + '');
+    }
   }
 
   /** Handles updating the at-include rules of uses of the core mixin. */

src/material/schematics/ng-update/test-cases/v19-mat-core-removal.spec.ts

@@ -6,7 +6,7 @@ import {MIGRATION_PATH} from '../../paths';
 const PROJECT_ROOT_DIR = '/projects/cdk-testing';
 const THEME_FILE_PATH = join(PROJECT_ROOT_DIR, 'src/theme.scss');
 
-describe('v15 legacy components migration', () => {
+describe('v19 mat.core migration', () => {
   let tree: UnitTestTree;
 
   /** Writes multiple lines to a file. */
@@ -73,5 +73,12 @@ describe('v15 legacy components migration', () => {
         ],
       });
     });
+
+    it('should not break if there is an invalid syntax', async () => {
+      await runSassMigrationTest('', {
+        old: [`@use '@angular/material' as mat;`, `.foo { content: '; }`],
+        new: [`@use '@angular/material' as mat;`, `.foo { content: '; }`],
+      });
+    });
   });
 });