refactor: remove custom error classes

* Removes the custom `MdError` class and refactors all of the classes that extended it into functions.
* Removes a few of the single-function `*-errors.ts` files and inlines their content.

Fixes #4317.

Author: crisbeto

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

@@ -5,7 +5,7 @@ import {
   NoConflictStyleCompatibilityMode,
   MAT_ELEMENTS_SELECTOR,
   MD_ELEMENTS_SELECTOR,
-  MdCompatibilityInvalidPrefixError,
+  getMdCompatibilityInvalidPrefixError,
 } from './compatibility';
 import {wrappedErrorMessage} from '../testing/wrapped-error-message';
 
@@ -34,7 +34,7 @@ describe('Style compatibility', () => {
     }));
 
     it('should throw an error when trying to use the "mat-" prefix', () => {
-      const expectedError = new MdCompatibilityInvalidPrefixError('mat', 'mat-checkbox');
+      const expectedError = getMdCompatibilityInvalidPrefixError('mat', 'mat-checkbox');
 
       expect(() => {
         TestBed.createComponent(ComponentWithMatCheckbox);
@@ -57,7 +57,7 @@ describe('Style compatibility', () => {
     });
 
     it('should throw an error when trying to use the "md-" prefix', () => {
-      const expectedError = new MdCompatibilityInvalidPrefixError('md', 'md-checkbox');
+      const expectedError = getMdCompatibilityInvalidPrefixError('md', 'md-checkbox');
 
       expect(() => {
         TestBed.createComponent(ComponentWithMdCheckbox);
@@ -75,7 +75,7 @@ describe('Style compatibility', () => {
     }));
 
     it('should throw an error when using the "md-" prefix', () => {
-      const expectedError = new MdCompatibilityInvalidPrefixError('md', 'md-checkbox');
+      const expectedError = getMdCompatibilityInvalidPrefixError('md', 'md-checkbox');
 
       expect(() => {
         TestBed.createComponent(ComponentWithMdCheckbox);

src/lib/core/compatibility/compatibility.ts

@@ -10,24 +10,20 @@ import {
   InjectionToken,
 } from '@angular/core';
 import {DOCUMENT} from '@angular/platform-browser';
-import {MdError} from '../errors/error';
 
 export const MATERIAL_COMPATIBILITY_MODE = new OpaqueToken('md-compatibility-mode');
 
 /** Injection token that configures whether the Material sanity checks are enabled. */
 export const MATERIAL_SANITY_CHECKS = new InjectionToken<boolean>('md-sanity-checks');
 
 /**
- * Exception thrown if the consumer has used an invalid Material prefix on a component.
+ * Returns an exception to be 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.`
-    );
-  }
+export function getMdCompatibilityInvalidPrefixError(prefix: string, nodeName: string) {
+  return new Error(`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. */
@@ -162,7 +158,7 @@ export class MatPrefixRejector {
     elementRef: ElementRef) {
 
     if (!isCompatibilityMode) {
-      throw new MdCompatibilityInvalidPrefixError('mat', elementRef.nativeElement.nodeName);
+      throw getMdCompatibilityInvalidPrefixError('mat', elementRef.nativeElement.nodeName);
     }
   }
 }
@@ -175,7 +171,7 @@ export class MdPrefixRejector {
     elementRef: ElementRef) {
 
     if (isCompatibilityMode) {
-      throw new MdCompatibilityInvalidPrefixError('md', elementRef.nativeElement.nodeName);
+      throw getMdCompatibilityInvalidPrefixError('md', elementRef.nativeElement.nodeName);
     }
   }
 }

src/lib/core/core.ts

@@ -89,9 +89,6 @@ export {MdLineModule, MdLine, MdLineSetter} from './line/line';
 // Style
 export * from './style/index';
 
-// Error
-export {MdError} from './errors/error';
-
 // Misc
 export {ComponentType} from './overlay/generic-component-type';
 

src/lib/core/errors/error.ts

@@ -1,63 +1,48 @@
-import {MdError} from '../errors/error';
-
 /**
- * Exception thrown when attempting to attach a null portal to a host.
+ * Throws an exception when attempting to attach a null portal to a host.
  * @docs-private
  */
-export class NullPortalError extends MdError {
-  constructor() {
-      super('Must provide a portal to attach');
-  }
+export function throwNullPortalError() {
+  throw new Error('Must provide a portal to attach');
 }
 
 /**
- * Exception thrown when attempting to attach a portal to a host that is already attached.
+ * Throws an exception when attempting to attach a portal to a host that is already attached.
  * @docs-private
  */
-export class PortalAlreadyAttachedError extends MdError {
-  constructor() {
-      super('Host already has a portal attached');
-  }
+export function throwPortalAlreadyAttachedError() {
+  throw new Error('Host already has a portal attached');
 }
 
 /**
- * Exception thrown when attempting to attach a portal to an already-disposed host.
+ * Throws an exception when attempting to attach a portal to an already-disposed host.
  * @docs-private
  */
-export class PortalHostAlreadyDisposedError extends MdError {
-  constructor() {
-      super('This PortalHost has already been disposed');
-  }
+export function throwPortalHostAlreadyDisposedError() {
+  throw new Error('This PortalHost has already been disposed');
 }
 
 /**
- * Exception thrown when attempting to attach an unknown portal type.
+ * Throws an exception when attempting to attach an unknown portal type.
  * @docs-private
  */
-export class UnknownPortalTypeError extends MdError {
-  constructor() {
-      super(
-        'Attempting to attach an unknown Portal type. ' +
-        'BasePortalHost accepts either a ComponentPortal or a TemplatePortal.');
-  }
+export function throwUnknownPortalTypeError() {
+  throw new Error('Attempting to attach an unknown Portal type. BasePortalHost accepts either' +
+                  'a ComponentPortal or a TemplatePortal.');
 }
 
 /**
- * Exception thrown when attempting to attach a portal to a null host.
+ * Throws an exception when attempting to attach a portal to a null host.
  * @docs-private
  */
-export class NullPortalHostError extends MdError {
-  constructor() {
-      super('Attempting to attach a portal to a null PortalHost');
-  }
+export function throwNullPortalHostError() {
+  throw new Error('Attempting to attach a portal to a null PortalHost');
 }
 
 /**
- * Exception thrown when attempting to detach a portal that is not attached.
- * @docs-private
+ * Throws an exception when attempting to detach a portal that is not attached.
+ * @docs-privatew
  */
-export class NoPortalAttachedError extends MdError {
-  constructor() {
-      super('Attempting to detach a portal that is not attached to a host');
-  }
+export function throwNoPortalAttachedError() {
+  throw new Error('Attempting to detach a portal that is not attached to a host');
 }

src/lib/core/portal/portal-errors.ts

@@ -6,12 +6,12 @@ import {
     Injector
 } from '@angular/core';
 import {
-    NullPortalHostError,
-    PortalAlreadyAttachedError,
-    NoPortalAttachedError,
-    NullPortalError,
-    PortalHostAlreadyDisposedError,
-    UnknownPortalTypeError
+    throwNullPortalHostError,
+    throwPortalAlreadyAttachedError,
+    throwNoPortalAttachedError,
+    throwNullPortalError,
+    throwPortalHostAlreadyDisposedError,
+    throwUnknownPortalTypeError
 } from './portal-errors';
 import {ComponentType} from '../overlay/generic-component-type';
 
@@ -27,11 +27,11 @@ export abstract class Portal<T> {
   /** Attach this portal to a host. */
   attach(host: PortalHost): T {
     if (host == null) {
-      throw new NullPortalHostError();
+      throwNullPortalHostError();
     }
 
     if (host.hasAttached()) {
-      throw new PortalAlreadyAttachedError();
+      throwPortalAlreadyAttachedError();
     }
 
     this._attachedHost = host;
@@ -42,7 +42,7 @@ export abstract class Portal<T> {
   detach(): void {
     let host = this._attachedHost;
     if (host == null) {
-      throw new NoPortalAttachedError();
+      throwNoPortalAttachedError();
     }
 
     this._attachedHost = null;
@@ -168,15 +168,15 @@ export abstract class BasePortalHost implements PortalHost {
 
   attach(portal: Portal<any>): any {
     if (!portal) {
-      throw new NullPortalError();
+      throwNullPortalError();
     }
 
     if (this.hasAttached()) {
-      throw new PortalAlreadyAttachedError();
+      throwPortalAlreadyAttachedError();
     }
 
     if (this._isDisposed) {
-      throw new PortalHostAlreadyDisposedError();
+      throwPortalHostAlreadyDisposedError();
     }
 
     if (portal instanceof ComponentPortal) {
@@ -187,7 +187,7 @@ export abstract class BasePortalHost implements PortalHost {
       return this.attachTemplatePortal(portal);
     }
 
-    throw new UnknownPortalTypeError();
+    throwUnknownPortalTypeError();
   }
 
   abstract attachComponentPortal<T>(portal: ComponentPortal<T>): ComponentRef<T>;

src/lib/core/portal/portal.ts

@@ -20,9 +20,16 @@ import {
 import {DOCUMENT} from '@angular/platform-browser';
 import {BasePortalHost, ComponentPortal, PortalHostDirective, TemplatePortal} from '../core';
 import {MdDialogConfig} from './dialog-config';
-import {MdDialogContentAlreadyAttachedError} from './dialog-errors';
 import {FocusTrapFactory, FocusTrap} from '../core/a11y/focus-trap';
 
+/**
+ * Throws an exception for the case when a ComponentPortal is
+ * attached to a DomPortalHost without an origin.
+ * @docs-private
+ */
+export function throwMdDialogContentAlreadyAttachedError() {
+  throw new Error('Attempting to attach dialog content after content is already attached');
+}
 
 /**
  * Internal component that wraps user-provided dialog content.
@@ -88,7 +95,7 @@ export class MdDialogContainer extends BasePortalHost {
    */
   attachComponentPortal<T>(portal: ComponentPortal<T>): ComponentRef<T> {
     if (this._portalHost.hasAttached()) {
-      throw new MdDialogContentAlreadyAttachedError();
+      throwMdDialogContentAlreadyAttachedError();
     }
 
     this._savePreviouslyFocusedElement();
@@ -101,7 +108,7 @@ export class MdDialogContainer extends BasePortalHost {
    */
   attachTemplatePortal(portal: TemplatePortal): Map<string, any> {
     if (this._portalHost.hasAttached()) {
-      throw new MdDialogContentAlreadyAttachedError();
+      throwMdDialogContentAlreadyAttachedError();
     }
 
     this._savePreviouslyFocusedElement();

src/lib/dialog/dialog-container.ts

@@ -13,7 +13,6 @@ import {
 import {MdGridTile} from './grid-tile';
 import {TileCoordinator} from './tile-coordinator';
 import {TileStyler, FitTileStyler, RatioTileStyler, FixedTileStyler} from './tile-styler';
-import {MdGridListColsError} from './grid-list-errors';
 import {Dir} from '../core';
 import {
   coerceToString,
@@ -97,7 +96,8 @@ export class MdGridList implements OnInit, AfterContentChecked {
   /** Throw a friendly error if cols property is missing */
   private _checkCols() {
     if (!this.cols) {
-      throw new MdGridListColsError();
+      throw new Error(`md-grid-list: must pass in number of columns. ` +
+                      `Example: <md-grid-list cols="3">`);
     }
   }