Enable the consistent-return ESLint rule

This rule is already enabled in mozilla-central, and helps ensure more consistent functions/methods, see https://searchfox.org/mozilla-central/rev/b9da45f63cb567244933c77b2c7e827a057d3f9b/tools/lint/eslint/eslint-plugin-mozilla/lib/configs/recommended.js#119-120

Please see https://eslint.org/docs/rules/consistent-return for additional information.

web/app.js

@@ -198,7 +198,7 @@ let PDFViewerApplication = {
   async _parseHashParameters() {
     if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('PRODUCTION') &&
         !AppOptions.get('pdfBugEnabled')) {
-      return;
+      return undefined;
     }
     const waitOn = [];
 
@@ -576,7 +576,7 @@ let PDFViewerApplication = {
     errorWrapper.setAttribute('hidden', 'true');
 
     if (!this.pdfLoadingTask) {
-      return;
+      return undefined;
     }
 
     let promise = this.pdfLoadingTask.destroy();
@@ -681,7 +681,7 @@ let PDFViewerApplication = {
       this.load(pdfDocument);
     }, (exception) => {
       if (loadingTask !== this.pdfLoadingTask) {
-        return; // Ignore errors for previously opened PDF files.
+        return undefined; // Ignore errors for previously opened PDF files.
       }
 
       let message = exception && exception.message;

web/download_manager.js

@@ -58,8 +58,8 @@ class DownloadManager {
 
   downloadData(data, filename, contentType) {
     if (navigator.msSaveBlob) { // IE10 and above
-      return navigator.msSaveBlob(new Blob([data], { type: contentType, }),
-                                  filename);
+      navigator.msSaveBlob(new Blob([data], { type: contentType, }), filename);
+      return;
     }
     let blobUrl = createObjectURL(data, contentType,
                                   this.disableCreateObjectURL);

web/grab_to_pan.js

@@ -221,6 +221,7 @@ function isLeftMouseReleased(event) {
     // Safari 6.0+
     return event.which === 0;
   }
+  return false;
 }
 
 export {

web/password_prompt.js

@@ -90,7 +90,7 @@ class PasswordPrompt {
     let password = this.input.value;
     if (password && password.length > 0) {
       this.close();
-      return this.updateCallback(password);
+      this.updateCallback(password);
     }
   }
 

web/pdf_document_properties.js

@@ -256,10 +256,10 @@ class PDFDocumentProperties {
   /**
    * @private
    */
-  _parseFileSize(fileSize = 0) {
+  async _parseFileSize(fileSize = 0) {
     let kb = fileSize / 1024;
     if (!kb) {
-      return Promise.resolve(undefined);
+      return undefined;
     } else if (kb < 1024) {
       return this.l10n.get('document_properties_kb', {
         size_kb: (+kb.toPrecision(3)).toLocaleString(),
@@ -275,9 +275,9 @@ class PDFDocumentProperties {
   /**
    * @private
    */
-  _parsePageSize(pageSizeInches, pagesRotation) {
+  async _parsePageSize(pageSizeInches, pagesRotation) {
     if (!pageSizeInches) {
-      return Promise.resolve(undefined);
+      return undefined;
     }
     // Take the viewer rotation into account as well; compare with Adobe Reader.
     if (pagesRotation % 180 !== 0) {
@@ -362,15 +362,15 @@ class PDFDocumentProperties {
   /**
    * @private
    */
-  _parseDate(inputDate) {
+  async _parseDate(inputDate) {
     const dateObject = PDFDateString.toDateObject(inputDate);
-    if (dateObject) {
-      const dateString = dateObject.toLocaleDateString();
-      const timeString = dateObject.toLocaleTimeString();
-      return this.l10n.get('document_properties_date_string',
-                           { date: dateString, time: timeString, },
-                           '{{date}}, {{time}}');
+    if (!dateObject) {
+      return undefined;
     }
+    return this.l10n.get('document_properties_date_string', {
+        date: dateObject.toLocaleDateString(),
+        time: dateObject.toLocaleTimeString(),
+      }, '{{date}}, {{time}}');
   }
 
   /**

web/pdf_print_service.js

@@ -292,6 +292,7 @@ window.addEventListener('keydown', function(event) {
   }
 }, true);
 if (hasAttachEvent) {
+  // eslint-disable-next-line consistent-return
   document.attachEvent('onkeydown', function(event) {
     event = event || window.event;
     if (event.keyCode === /* P= */ 80 && event.ctrlKey) {