refactor(localize): simplify adding condition diagnostics (#36792)

Previously the `missingTranslation` option had to be checked before calling
`warn` or `error` on the `diagnostics` object.

Now this boilerplate is hidden inside the `Diagnostics.add()` method, which
will open it up to being used for other conditional diagnostics.

PR Close #36792

packages/localize/src/tools/src/diagnostics.ts

@@ -6,6 +6,11 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+/**
+ * How to handle potential diagnostics.
+ */
+export type DiagnosticHandlingStrategy = 'error'|'warning'|'ignore';
+
 /**
  * This class is used to collect and then report warnings and errors that occur during the execution
  * of the tools.
@@ -15,6 +20,11 @@ export class Diagnostics {
   get hasErrors() {
     return this.messages.some(m => m.type === 'error');
   }
+  add(type: DiagnosticHandlingStrategy, message: string) {
+    if (type !== 'ignore') {
+      this.messages.push({type, message});
+    }
+  }
   warn(message: string) {
     this.messages.push({type: 'warning', message});
   }

packages/localize/src/tools/src/source_file_utils.ts

@@ -8,7 +8,8 @@
 import {ɵisMissingTranslationError, ɵmakeTemplateObject, ɵParsedTranslation, ɵSourceLocation, ɵtranslate} from '@angular/localize';
 import {NodePath} from '@babel/traverse';
 import * as t from '@babel/types';
-import {Diagnostics} from './diagnostics';
+
+import {DiagnosticHandlingStrategy, Diagnostics} from './diagnostics';
 
 /**
  * Is the given `expression` the global `$localize` identifier?
@@ -299,15 +300,10 @@ export function isArrayOfExpressions(nodes: t.Node[]): nodes is t.Expression[] {
 
 /** Options that affect how the `makeEsXXXTranslatePlugin()` functions work. */
 export interface TranslatePluginOptions {
-  missingTranslation?: MissingTranslationStrategy;
+  missingTranslation?: DiagnosticHandlingStrategy;
   localizeName?: string;
 }
 
-/**
- * How to handle missing translations.
- */
-export type MissingTranslationStrategy = 'error'|'warning'|'ignore';
-
 /**
  * Translate the text of the given message, using the given translations.
  *
@@ -316,16 +312,12 @@ export type MissingTranslationStrategy = 'error'|'warning'|'ignore';
 export function translate(
     diagnostics: Diagnostics, translations: Record<string, ɵParsedTranslation>,
     messageParts: TemplateStringsArray, substitutions: readonly any[],
-    missingTranslation: MissingTranslationStrategy): [TemplateStringsArray, readonly any[]] {
+    missingTranslation: DiagnosticHandlingStrategy): [TemplateStringsArray, readonly any[]] {
   try {
     return ɵtranslate(translations, messageParts, substitutions);
   } catch (e) {
     if (ɵisMissingTranslationError(e)) {
-      if (missingTranslation === 'error') {
-        diagnostics.error(e.message);
-      } else if (missingTranslation === 'warning') {
-        diagnostics.warn(e.message);
-      }
+      diagnostics.add(missingTranslation, e.message);
       // Return the parsed message because this will have the meta blocks stripped
       return [
         ɵmakeTemplateObject(e.parsedMessage.messageParts, e.parsedMessage.messageParts),

packages/localize/src/tools/src/translate/main.ts

@@ -84,7 +84,7 @@ if (require.main === module) {
   const translationFilePaths: string[] = options['t'];
   const outputPathFn = getOutputPathFn(options['o']);
   const diagnostics = new Diagnostics();
-  const missingTranslation: MissingTranslationStrategy = options['m'];
+  const missingTranslation: DiagnosticHandlingStrategy = options['m'];
   const sourceLocale: string|undefined = options['l'];
   const translationFileLocales: string[] = options['target-locales'] || [];
 
@@ -134,7 +134,7 @@ export interface TranslateFilesOptions {
   /**
    * How to handle missing translations.
    */
-  missingTranslation: MissingTranslationStrategy;
+  missingTranslation: DiagnosticHandlingStrategy;
   /**
    * The locale of the source files.
    * If this is provided then a copy of the application will be created with no translation but just