1 files changed, 81 insertions, 12 deletions

diff --git a/browser/components/translations/content/TranslationsPanelShared.sys.mjs b/browser/components/translations/content/TranslationsPanelShared.sys.mjs
index 570528df3f..f5045f57e0 100644
--- a/browser/components/translations/content/TranslationsPanelShared.sys.mjs
+++ b/browser/components/translations/content/TranslationsPanelShared.sys.mjs
@@ -11,9 +11,53 @@ ChromeUtils.defineESModuleGetters(lazy, {
 /**
  * A class containing static functionality that is shared by both
  * the FullPageTranslationsPanel and SelectTranslationsPanel classes.
+ *
+ * It is recommended to read the documentation above the TranslationsParent class
+ * definition to understand the scope of the Translations architecture throughout
+ * Firefox.
+ *
+ * @see TranslationsParent
+ *
+ * The static instance of this class is a singleton in the parent process, and is
+ * available throughout all windows and tabs, just like the static instance of
+ * the TranslationsParent class.
+ *
+ * Unlike the TranslationsParent, this class is never instantiated as an actor
+ * outside of the static-context functionality defined below.
  */
 export class TranslationsPanelShared {
-  static #langListsInitState = new Map();
+  /**
+   * A map from Translations Panel instances to their initialized states.
+   * There is one instance of each panel per top ChromeWindow in Firefox.
+   *
+   * See the documentation above the TranslationsParent class for a detailed
+   * explanation of the translations architecture throughout Firefox.
+   *
+   * @see TranslationsParent
+   *
+   * @type {Map<FullPageTranslationsPanel | SelectTranslationsPanel, string>}
+   */
+  static #langListsInitState = new WeakMap();
+
+  /**
+   * True if the next language-list initialization to fail for testing.
+   *
+   * @see TranslationsPanelShared.ensureLangListsBuilt
+   *
+   * @type {boolean}
+   */
+  static #simulateLangListError = false;
+
+  /**
+   * Clears cached data regarding the initialization state of the
+   * FullPageTranslationsPanel or the SelectTranslationsPanel.
+   *
+   * This is only needed for test runners to ensure that each test
+   * starts from a clean slate.
+   */
+  static clearCache() {
+    this.#langListsInitState = new WeakMap();
+  }
 
   /**
    * Defines lazy getters for accessing elements in the document based on provided entries.
@@ -46,13 +90,25 @@ export class TranslationsPanelShared {
   }
 
   /**
+   * Ensures that the next call to ensureLangListBuilt wil fail
+   * for the purpose of testing the error state.
+   *
+   * @see TranslationsPanelShared.ensureLangListsBuilt
+   *
+   * @type {boolean}
+   */
+  static simulateLangListError() {
+    this.#simulateLangListError = true;
+  }
+
+  /**
    * Retrieves the initialization state of language lists for the specified panel.
    *
    * @param {FullPageTranslationsPanel | SelectTranslationsPanel} panel
    *   - The panel for which to look up the state.
    */
   static getLangListsInitState(panel) {
-    return TranslationsPanelShared.#langListsInitState.get(panel.id);
+    return TranslationsPanelShared.#langListsInitState.get(panel);
   }
 
   /**
@@ -64,17 +120,17 @@ export class TranslationsPanelShared {
    * @param {FullPageTranslationsPanel | SelectTranslationsPanel} panel
    *   - The panel for which to ensure language lists are built.
    */
-  static async ensureLangListsBuilt(document, panel, innerWindowId) {
-    const { id } = panel;
-    switch (
-      TranslationsPanelShared.#langListsInitState.get(`${id}-${innerWindowId}`)
-    ) {
+  static async ensureLangListsBuilt(document, panel) {
+    const { panel: panelElement } = panel.elements;
+    switch (TranslationsPanelShared.#langListsInitState.get(panel)) {
       case "initialized":
         // This has already been initialized.
         return;
       case "error":
       case undefined:
-        // attempt to initialize
+        // Set the error state in case there is an early exit at any point.
+        // This will be set to "initialized" if everything succeeds.
+        TranslationsPanelShared.#langListsInitState.set(panel, "error");
         break;
       default:
         throw new Error(
@@ -88,18 +144,28 @@ export class TranslationsPanelShared {
       await lazy.TranslationsParent.getSupportedLanguages();
 
     // Verify that we are in a proper state.
-    if (languagePairs.length === 0) {
+    if (languagePairs.length === 0 || this.#simulateLangListError) {
+      this.#simulateLangListError = false;
       throw new Error("No translation languages were retrieved.");
     }
 
-    const fromPopups = panel.querySelectorAll(
+    const fromPopups = panelElement.querySelectorAll(
       ".translations-panel-language-menupopup-from"
     );
-    const toPopups = panel.querySelectorAll(
+    const toPopups = panelElement.querySelectorAll(
       ".translations-panel-language-menupopup-to"
     );
 
     for (const popup of fromPopups) {
+      // For the moment, the FullPageTranslationsPanel includes its own
+      // menu item for "Choose another language" as the first item in the list
+      // with an empty-string for its value. The SelectTranslationsPanel has
+      // only languages in its list with BCP-47 tags for values. As such,
+      // this loop works for both panels, to remove all of the languages
+      // from the list, but ensuring that any empty-string items are retained.
+      while (popup.lastChild?.value) {
+        popup.lastChild.remove();
+      }
       for (const { langTag, displayName } of fromLanguages) {
         const fromMenuItem = document.createXULElement("menuitem");
         fromMenuItem.setAttribute("value", langTag);
@@ -109,6 +175,9 @@ export class TranslationsPanelShared {
     }
 
     for (const popup of toPopups) {
+      while (popup.lastChild?.value) {
+        popup.lastChild.remove();
+      }
       for (const { langTag, displayName } of toLanguages) {
         const toMenuItem = document.createXULElement("menuitem");
         toMenuItem.setAttribute("value", langTag);
@@ -117,6 +186,6 @@ export class TranslationsPanelShared {
       }
     }
 
-    TranslationsPanelShared.#langListsInitState.set(id, "initialized");
+    TranslationsPanelShared.#langListsInitState.set(panel, "initialized");
   }
 }