feat(ValidationMessageProvider): include displayName arg

fixes #328

Now the getDisplayName method will be called for all properties, even those that have a display name already configured via the fluent rule API's displayName method.

src/implementation/standard-validator.ts

@@ -63,8 +63,8 @@ export class StandardValidator extends Validator {
   private getMessage(rule: Rule<any, any>, object: any, value: any): string {
     const expression: Expression = rule.message || this.messageProvider.getMessage(rule.messageKey);
     let { name: propertyName, displayName } = rule.property;
-    if (displayName === null && propertyName !== null) {
-      displayName = this.messageProvider.getDisplayName(propertyName);
+    if (propertyName !== null) {
+      displayName = this.messageProvider.getDisplayName(propertyName, displayName);
     }
     const overrideContext: any = {
       $displayName: displayName,

src/implementation/validation-messages.ts

@@ -46,12 +46,16 @@ export class ValidationMessageProvider {
   }
 
   /**
-   * When a display name is not provided, this method is used to formulate
-   * a display name using the property name.
+   * Formulates a property display name using the property name and the configured
+   * displayName (if provided).
    * Override this with your own custom logic.
    * @param propertyName The property name.
    */
-  public getDisplayName(propertyName: string): string {
+  public getDisplayName(propertyName: string, displayName: string|null|undefined): string {
+    if (displayName !== null && displayName !== undefined) {
+      return displayName;
+    }
+
     // split on upper-case letters.
     const words = propertyName.split(/(?=[A-Z])/).join(' ');
     // capitalize first letter.

test/validation-messages.ts

@@ -0,0 +1,24 @@
+import { Container } from 'aurelia-dependency-injection';
+import { BindingLanguage } from 'aurelia-templating';
+import { TemplatingBindingLanguage } from 'aurelia-templating-binding';
+import { ValidationMessageProvider } from '../src/aurelia-validation';
+
+describe('ValidationMessageProvider', () => {
+  let messageProvider: ValidationMessageProvider;
+
+  beforeAll(() => {
+    const container = new Container();
+    container.registerInstance(BindingLanguage, container.get(TemplatingBindingLanguage));
+    messageProvider = container.get(ValidationMessageProvider);
+  });
+
+  it('computes display name', () => {
+    expect(messageProvider.getDisplayName('foo', null)).toBe('Foo');
+    expect(messageProvider.getDisplayName('fooBar', null)).toBe('Foo Bar');
+    expect(messageProvider.getDisplayName('foo bar', null)).toBe('Foo bar');
+    expect(messageProvider.getDisplayName('foo', undefined)).toBe('Foo');
+    expect(messageProvider.getDisplayName('fooBar', undefined)).toBe('Foo Bar');
+    expect(messageProvider.getDisplayName('foo bar', undefined)).toBe('Foo bar');
+    expect(messageProvider.getDisplayName('foo', 'hello')).toBe('hello');
+  });
+});