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.

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);
 }