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.

.eslintrc

@@ -57,6 +57,7 @@
 
     // Best Practices
     "accessor-pairs": ["error", { "setWithoutGet": true, }],
+    "consistent-return": "error",
     "curly": ["error", "all"],
     "eqeqeq": ["error", "always"],
     "no-caller": "error",

extensions/chromium/extension-router.js

@@ -43,7 +43,7 @@ limitations under the License.
     // Find the (url-encoded) colon and verify that the scheme is whitelisted.
     var schemeIndex = url.search(/:|%3A/i);
     if (schemeIndex === -1) {
-      return;
+      return undefined;
     }
     var scheme = url.slice(0, schemeIndex).toLowerCase();
     if (schemes.includes(scheme)) {
@@ -53,6 +53,7 @@ limitations under the License.
       }
       return url;
     }
+    return undefined;
   }
 
   // TODO(rob): Use declarativeWebRequest once declared URL-encoding is
@@ -72,6 +73,7 @@ limitations under the License.
       console.log('Redirecting ' + details.url + ' to ' + url);
       return { redirectUrl: url, };
     }
+    return undefined;
   }, {
     types: ['main_frame', 'sub_frame'],
     urls: schemes.map(function(scheme) {

extensions/chromium/pdfHandler.js

@@ -59,6 +59,7 @@ function getHeaderFromHeaders(headers, headerName) {
       return header;
     }
   }
+  return undefined;
 }
 
 /**
@@ -86,6 +87,7 @@ function isPdfFile(details) {
       }
     }
   }
+  return false;
 }
 
 /**
@@ -108,16 +110,17 @@ function getHeadersWithContentDispositionAttachment(details) {
     cdHeader.value = 'attachment' + cdHeader.value.replace(/^[^;]+/i, '');
     return { responseHeaders: headers, };
   }
+  return undefined;
 }
 
 chrome.webRequest.onHeadersReceived.addListener(
   function(details) {
     if (details.method !== 'GET') {
       // Don't intercept POST requests until http://crbug.com/104058 is fixed.
-      return;
+      return undefined;
     }
     if (!isPdfFile(details)) {
-      return;
+      return undefined;
     }
     if (isPdfDownloadable(details)) {
       // Force download by ensuring that Content-Disposition: attachment is set
@@ -142,7 +145,7 @@ chrome.webRequest.onHeadersReceived.addListener(
 chrome.webRequest.onBeforeRequest.addListener(
   function(details) {
     if (isPdfDownloadable(details)) {
-      return;
+      return undefined;
     }
 
     var viewerUrl = getViewerURL(details.url);
@@ -200,7 +203,7 @@ chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
     // sensitive (local) file in a frame.
     if (!sender.tab) {
       sendResponse('');
-      return;
+      return undefined;
     }
     // TODO: This should be the URL of the parent frame, not the tab. But
     // chrome-extension:-URLs are not visible in the webNavigation API
@@ -209,11 +212,11 @@ chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
     var parentUrl = sender.tab.url;
     if (!parentUrl) {
       sendResponse('');
-      return;
+      return undefined;
     }
     if (parentUrl.lastIndexOf('file:', 0) === 0) {
       sendResponse('file://');
-      return;
+      return undefined;
     }
     // The regexp should always match for valid URLs, but in case it doesn't,
     // just give the full URL (e.g. data URLs).
@@ -240,6 +243,7 @@ chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
       });
     }
   }
+  return undefined;
 });
 
 // Remove keys from storage that were once part of the deleted feature-detect.js

extensions/chromium/preserve-referer.js

@@ -130,7 +130,7 @@ chrome.runtime.onConnect.addListener(function onReceivePort(port) {
 
   function onBeforeSendHeaders(details) {
     if (details.frameId !== frameId) {
-      return;
+      return undefined;
     }
     var headers = details.requestHeaders;
     var refererHeader = getHeaderFromHeaders(headers, 'referer');
@@ -141,15 +141,15 @@ chrome.runtime.onConnect.addListener(function onReceivePort(port) {
         refererHeader.value.lastIndexOf('chrome-extension:', 0) !== 0) {
       // Sanity check. If the referer is set, and the value is not the URL of
       // this extension, then the request was not initiated by this extension.
-      return;
+      return undefined;
     }
     refererHeader.value = referer;
     return { requestHeaders: headers, };
   }
 
   function exposeOnHeadersReceived(details) {
     if (details.frameId !== frameId) {
-      return;
+      return undefined;
     }
     var headers = details.responseHeaders;
     var aceh = getHeaderFromHeaders(headers, 'access-control-expose-headers');

gulpfile.js

@@ -365,7 +365,7 @@ function getTempFile(prefix, suffix) {
 
 function createTestSource(testsName, bot) {
   var source = stream.Readable({ objectMode: true, });
-  source._read = function () {
+  source._read = function() {
     console.log();
     console.log('### Running ' + testsName + ' tests');
 
@@ -409,6 +409,7 @@ function createTestSource(testsName, bot) {
     testProcess.on('close', function (code) {
       source.push(null);
     });
+    return undefined;
   };
   return source;
 }
@@ -1245,9 +1246,10 @@ gulp.task('gh-pages-prepare', function () {
 gulp.task('wintersmith', function (done) {
   var wintersmith = require('wintersmith');
   var env = wintersmith('docs/config.json');
-  env.build(GH_PAGES_DIR, function (error) {
+  env.build(GH_PAGES_DIR, function(error) {
     if (error) {
-      return done(error);
+      done(error);
+      return;
     }
     replaceInFile(GH_PAGES_DIR + '/getting_started/index.html',
                   /STABLE_VERSION/g, config.stableVersion);

src/core/annotation.js

@@ -48,7 +48,7 @@ class AnnotationFactory {
   static _create(xref, ref, pdfManager, idFactory) {
     let dict = xref.fetchIfRef(ref);
     if (!isDict(dict)) {
-      return;
+      return undefined;
     }
     let id = isRef(ref) ? ref.toString() : `annot_${idFactory.createObjId()}`;
 
@@ -432,7 +432,7 @@ class Annotation {
   loadResources(keys) {
     return this.appearance.dict.getAsync('Resources').then((resources) => {
       if (!resources) {
-        return;
+        return undefined;
       }
       let objectLoader = new ObjectLoader(resources, keys, resources.xref);
 

src/core/evaluator.js

@@ -302,12 +302,12 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
 
       if (!(w && isNum(w)) || !(h && isNum(h))) {
         warn('Image dimensions are missing, or not numbers.');
-        return;
+        return undefined;
       }
       var maxImageSize = this.options.maxImageSize;
       if (maxImageSize !== -1 && w * h > maxImageSize) {
         warn('Image exceeded maximum allowed size and was removed.');
-        return;
+        return undefined;
       }
 
       var imageMask = (dict.get('ImageMask', 'IM') || false);
@@ -343,7 +343,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
             args,
           };
         }
-        return;
+        return undefined;
       }
 
       var softMask = (dict.get('SMask', 'SM') || false);
@@ -364,7 +364,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
         // any other kind.
         imgData = imageObj.createImageData(/* forceRGBA = */ true);
         operatorList.addOp(OPS.paintInlineImageXObject, [imgData]);
-        return;
+        return undefined;
       }
 
       const nativeImageDecoderSupport = forceDisableNativeImageDecoder ?
@@ -452,6 +452,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
         }
         this.handler.send('obj', [objId, this.pageIndex, 'Image', imgData],
           [imgData.data.buffer]);
+        return undefined;
       }).catch((reason) => {
         warn('Unable to decode image: ' + reason);
 
@@ -460,6 +461,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
                                               [objId, 'FontType3Res', null]);
         }
         this.handler.send('obj', [objId, this.pageIndex, 'Image', null]);
+        return undefined;
       });
 
       if (this.parsingType3Font) {
@@ -476,6 +478,7 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
           args,
         };
       }
+      return undefined;
     },
 
     handleSMask: function PartialEvaluator_handleSmask(smask, resources,

src/core/jpg.js

@@ -973,6 +973,7 @@ var JpegImage = (function JpegImageClosure() {
         });
       }
       this.numComponents = this.components.length;
+      return undefined;
     },
 
     _getLinearizedBlockData(width, height, isSourcePDF = false) {

src/core/obj.js

@@ -266,6 +266,7 @@ class Catalog {
     } else if (this.catDict.has('Dests')) { // Simple destination dictionary.
       return this.catDict.get('Dests');
     }
+    return undefined;
   }
 
   get pageLabels() {
@@ -1596,7 +1597,7 @@ var XRef = (function XRefClosure() {
       }
 
       if (recoveryMode) {
-        return;
+        return undefined;
       }
       throw new XRefParseException();
     },

src/core/operator_list.js

@@ -71,6 +71,7 @@ var QueueOptimizer = (function QueueOptimizerClosure() {
         case 3:
           return fnArray[i] === OPS.restore;
       }
+      throw new Error(`iterateInlineImageGroup - invalid pos: ${pos}`);
     },
     function foundInlineImageGroup(context, i) {
       var MIN_IMAGES_IN_INLINE_IMAGES_BLOCK = 10;
@@ -173,6 +174,7 @@ var QueueOptimizer = (function QueueOptimizerClosure() {
         case 3:
           return fnArray[i] === OPS.restore;
       }
+      throw new Error(`iterateImageMaskGroup - invalid pos: ${pos}`);
     },
     function foundImageMaskGroup(context, i) {
       var MIN_IMAGES_IN_MASKS_BLOCK = 10;
@@ -266,7 +268,7 @@ var QueueOptimizer = (function QueueOptimizerClosure() {
       return argsArray[iFirstTransform][1] === 0 &&
              argsArray[iFirstTransform][2] === 0;
     },
-    function (context, i) {
+    function iterateImageGroup(context, i) {
       var fnArray = context.fnArray, argsArray = context.argsArray;
       var iFirstSave = context.iCurr - 3;
       var pos = (i - iFirstSave) % 4;
@@ -300,6 +302,7 @@ var QueueOptimizer = (function QueueOptimizerClosure() {
         case 3:
           return fnArray[i] === OPS.restore;
       }
+      throw new Error(`iterateImageGroup - invalid pos: ${pos}`);
     },
     function (context, i) {
       var MIN_IMAGES_IN_BLOCK = 3;
@@ -346,7 +349,7 @@ var QueueOptimizer = (function QueueOptimizerClosure() {
   addState(InitialState,
     [OPS.beginText, OPS.setFont, OPS.setTextMatrix, OPS.showText, OPS.endText],
     null,
-    function (context, i) {
+    function iterateShowTextGroup(context, i) {
       var fnArray = context.fnArray, argsArray = context.argsArray;
       var iFirstSave = context.iCurr - 4;
       var pos = (i - iFirstSave) % 5;
@@ -372,6 +375,7 @@ var QueueOptimizer = (function QueueOptimizerClosure() {
         case 4:
           return fnArray[i] === OPS.endText;
       }
+      throw new Error(`iterateShowTextGroup - invalid pos: ${pos}`);
     },
     function (context, i) {
       var MIN_CHARS_IN_BLOCK = 3;

src/display/api.js

@@ -2021,13 +2021,14 @@ class WorkerTransport {
 
     messageHandler.on('obj', function(data) {
       if (this.destroyed) {
-        return; // Ignore any pending requests if the worker was terminated.
+        // Ignore any pending requests if the worker was terminated.
+        return undefined;
       }
 
       const [id, pageIndex, type, imageData] = data;
       const pageProxy = this.pageCache[pageIndex];
       if (pageProxy.objs.has(id)) {
-        return;
+        return undefined;
       }
 
       switch (type) {
@@ -2064,6 +2065,7 @@ class WorkerTransport {
         default:
           throw new Error(`Got unknown object type ${type}`);
       }
+      return undefined;
     }, this);
 
     messageHandler.on('DocProgress', function(data) {

src/display/canvas.js

@@ -1435,7 +1435,7 @@ var CanvasGraphics = (function CanvasGraphicsClosure() {
 
       var fontSize = current.fontSize;
       if (fontSize === 0) {
-        return;
+        return undefined;
       }
 
       var ctx = this.ctx;

src/display/font_loader.js

@@ -64,7 +64,7 @@ class BaseFontLoader {
   async bind(font) {
     // Add the font to the DOM only once; skip if the font is already loaded.
     if (font.attached || font.missingFile) {
-      return;
+      return undefined;
     }
     font.attached = true;
 
@@ -83,7 +83,7 @@ class BaseFontLoader {
           throw ex;
         }
       }
-      return; // The font was, asynchronously, loaded.
+      return undefined; // The font was, asynchronously, loaded.
     }
 
     // !this.isFontLoadingAPISupported
@@ -92,13 +92,14 @@ class BaseFontLoader {
       this.insertRule(rule);
 
       if (this.isSyncFontLoadingSupported) {
-        return; // The font was, synchronously, loaded.
+        return undefined; // The font was, synchronously, loaded.
       }
       return new Promise((resolve) => {
         const request = this._queueLoadingCallback(resolve);
         this._prepareFontLoadEvent([rule], [font], request);
       });
     }
+    return undefined;
   }
 
   _queueLoadingCallback(callback) {

src/shared/message_handler.js

@@ -20,7 +20,7 @@ import {
 
 async function resolveCall(fn, args, thisArg = null) {
   if (!fn) {
-    return;
+    return undefined;
   }
   return fn.apply(thisArg, args);
 }