fix(compatibility): throw better error when wrong prefix is used (#3871)

Throws a slightly better error when the wrong prefix is used. The error now includes the node name of the offending element, which should make it easier to pinpoint the issue.

src/lib/core/compatibility/compatibility.spec.ts

@@ -4,8 +4,10 @@ import {MdCheckboxModule} from '../../checkbox/index';
 import {
   NoConflictStyleCompatibilityMode,
   MAT_ELEMENTS_SELECTOR,
-  MD_ELEMENTS_SELECTOR
+  MD_ELEMENTS_SELECTOR,
+  MdCompatibilityInvalidPrefixError,
 } from './compatibility';
+import {wrappedErrorMessage} from '../testing/wrapped-error-message';
 
 
 describe('Style compatibility', () => {
@@ -32,9 +34,11 @@ describe('Style compatibility', () => {
     }));
 
     it('should throw an error when trying to use the "mat-" prefix', () => {
+      const expectedError = new MdCompatibilityInvalidPrefixError('mat', 'mat-checkbox');
+
       expect(() => {
         TestBed.createComponent(ComponentWithMatCheckbox);
-      }).toThrowError(/The "mat-" prefix cannot be used out of ng-material v1 compatibility mode/);
+      }).toThrowError(wrappedErrorMessage(expectedError));
     });
   });
 
@@ -53,9 +57,11 @@ describe('Style compatibility', () => {
     });
 
     it('should throw an error when trying to use the "md-" prefix', () => {
+      const expectedError = new MdCompatibilityInvalidPrefixError('md', 'md-checkbox');
+
       expect(() => {
         TestBed.createComponent(ComponentWithMdCheckbox);
-      }).toThrowError(/The "md-" prefix cannot be used in ng-material v1 compatibility mode/);
+      }).toThrowError(wrappedErrorMessage(expectedError));
     });
   });
 
@@ -69,9 +75,11 @@ describe('Style compatibility', () => {
     }));
 
     it('should throw an error when using the "md-" prefix', () => {
-       expect(() => {
+      const expectedError = new MdCompatibilityInvalidPrefixError('md', 'md-checkbox');
+
+      expect(() => {
         TestBed.createComponent(ComponentWithMdCheckbox);
-      }).toThrowError(/The "md-" prefix cannot be used in ng-material v1 compatibility mode/);
+      }).toThrowError(wrappedErrorMessage(expectedError));
     });
 
     it('should not throw an error when using the "mat-" prefix', () => {

src/lib/core/compatibility/compatibility.ts

@@ -6,14 +6,29 @@ import {
   Inject,
   Optional,
   isDevMode,
+  ElementRef,
 } from '@angular/core';
 import {DOCUMENT} from '@angular/platform-browser';
+import {MdError} from '../errors/error';
 
 /** Whether we've done the global sanity checks (e.g. a theme is loaded, there is a doctype). */
 let hasDoneGlobalChecks = false;
 
 export const MATERIAL_COMPATIBILITY_MODE = new OpaqueToken('md-compatibility-mode');
 
+/**
+ * Exception thrown if the consumer has used an invalid Material prefix on a component.
+ * @docs-private
+ */
+export class MdCompatibilityInvalidPrefixError extends MdError {
+  constructor(prefix: string, nodeName: string) {
+    super(
+      `The "${prefix}-" prefix cannot be used in ng-material v1 compatibility mode. ` +
+      `It was used on an "${nodeName.toLowerCase()}" element.`
+    );
+  }
+}
+
 /** Selector that matches all elements that may have style collisions with AngularJS Material. */
 export const MAT_ELEMENTS_SELECTOR = `
   [mat-button],
@@ -137,19 +152,25 @@ export const MD_ELEMENTS_SELECTOR = `
 /** Directive that enforces that the `mat-` prefix cannot be used. */
 @Directive({selector: MAT_ELEMENTS_SELECTOR})
 export class MatPrefixRejector {
-  constructor(@Optional() @Inject(MATERIAL_COMPATIBILITY_MODE) isCompatibilityMode: boolean) {
+  constructor(
+    @Optional() @Inject(MATERIAL_COMPATIBILITY_MODE) isCompatibilityMode: boolean,
+    elementRef: ElementRef) {
+
     if (!isCompatibilityMode) {
-      throw Error('The "mat-" prefix cannot be used out of ng-material v1 compatibility mode.');
+      throw new MdCompatibilityInvalidPrefixError('mat', elementRef.nativeElement.nodeName);
     }
   }
 }
 
 /** Directive that enforces that the `md-` prefix cannot be used. */
 @Directive({selector: MD_ELEMENTS_SELECTOR})
 export class MdPrefixRejector {
-  constructor(@Optional() @Inject(MATERIAL_COMPATIBILITY_MODE) isCompatibilityMode: boolean) {
+  constructor(
+    @Optional() @Inject(MATERIAL_COMPATIBILITY_MODE) isCompatibilityMode: boolean,
+    elementRef: ElementRef) {
+
     if (isCompatibilityMode) {
-      throw Error('The "md-" prefix cannot be used in ng-material v1 compatibility mode.');
+      throw new MdCompatibilityInvalidPrefixError('md', elementRef.nativeElement.nodeName);
     }
   }
 }