Re-factor the handling of *empty* Name-instances (PR 13612 follow-up)

src/core/evaluator.js

@@ -1540,7 +1540,7 @@ class PartialEvaluator {
       timeSlotManager.reset();
 
       const operation = {};
-      let stop, i, ii, cs, name;
+      let stop, i, ii, cs, name, isValidName;
       while (!(stop = timeSlotManager.check())) {
         // The arguments parsed by read() are used beyond this loop, so we
         // cannot reuse the same array on each iteration. Therefore we pass
@@ -1556,8 +1556,10 @@ class PartialEvaluator {
         switch (fn | 0) {
           case OPS.paintXObject:
             // eagerly compile XForm objects
+            isValidName = args[0] instanceof Name;
             name = args[0].name;
-            if (name) {
+
+            if (isValidName) {
               const localImage = localImageCache.getByName(name);
               if (localImage) {
                 operatorList.addOp(localImage.fn, localImage.args);
@@ -1568,7 +1570,7 @@ class PartialEvaluator {
 
             next(
               new Promise(function (resolveXObject, rejectXObject) {
-                if (!name) {
+                if (!isValidName) {
                   throw new FormatError("XObject must be referred to by name.");
                 }
 
@@ -1922,8 +1924,10 @@ class PartialEvaluator {
             fn = OPS.shadingFill;
             break;
           case OPS.setGState:
+            isValidName = args[0] instanceof Name;
             name = args[0].name;
-            if (name) {
+
+            if (isValidName) {
               const localGStateObj = localGStateCache.getByName(name);
               if (localGStateObj) {
                 if (localGStateObj.length > 0) {
@@ -1936,7 +1940,7 @@ class PartialEvaluator {
 
             next(
               new Promise(function (resolveGState, rejectGState) {
-                if (!name) {
+                if (!isValidName) {
                   throw new FormatError("GState must be referred to by name.");
                 }
 
@@ -2823,14 +2827,16 @@ class PartialEvaluator {
               xobjs = resources.get("XObject") || Dict.empty;
             }
 
+            var isValidName = args[0] instanceof Name;
             var name = args[0].name;
-            if (name && emptyXObjectCache.getByName(name)) {
+
+            if (isValidName && emptyXObjectCache.getByName(name)) {
               break;
             }
 
             next(
               new Promise(function (resolveXObject, rejectXObject) {
-                if (!name) {
+                if (!isValidName) {
                   throw new FormatError("XObject must be referred to by name.");
                 }
 
@@ -2935,14 +2941,16 @@ class PartialEvaluator {
             );
             return;
           case OPS.setGState:
+            isValidName = args[0] instanceof Name;
             name = args[0].name;
-            if (name && emptyGStateCache.getByName(name)) {
+
+            if (isValidName && emptyGStateCache.getByName(name)) {
               break;
             }
 
             next(
               new Promise(function (resolveGState, rejectGState) {
-                if (!name) {
+                if (!isValidName) {
                   throw new FormatError("GState must be referred to by name.");
                 }
 

src/core/image_utils.js

@@ -47,7 +47,7 @@ class BaseLocalCache {
 
 class LocalImageCache extends BaseLocalCache {
   set(name, ref = null, data) {
-    if (!name) {
+    if (typeof name !== "string") {
       throw new Error('LocalImageCache.set - expected "name" argument.');
     }
     if (ref) {
@@ -68,7 +68,7 @@ class LocalImageCache extends BaseLocalCache {
 
 class LocalColorSpaceCache extends BaseLocalCache {
   set(name = null, ref = null, data) {
-    if (!name && !ref) {
+    if (typeof name !== "string" && !ref) {
       throw new Error(
         'LocalColorSpaceCache.set - expected "name" and/or "ref" argument.'
       );
@@ -77,7 +77,7 @@ class LocalColorSpaceCache extends BaseLocalCache {
       if (this._imageCache.has(ref)) {
         return;
       }
-      if (name) {
+      if (name !== null) {
         // Optional when `ref` is defined.
         this._nameRefMap.set(name, ref);
       }
@@ -114,7 +114,7 @@ class LocalFunctionCache extends BaseLocalCache {
 
 class LocalGStateCache extends BaseLocalCache {
   set(name, ref = null, data) {
-    if (!name) {
+    if (typeof name !== "string") {
       throw new Error('LocalGStateCache.set - expected "name" argument.');
     }
     if (ref) {
@@ -135,7 +135,7 @@ class LocalGStateCache extends BaseLocalCache {
 
 class LocalTilingPatternCache extends BaseLocalCache {
   set(name, ref = null, data) {
-    if (!name) {
+    if (typeof name !== "string") {
       throw new Error(
         'LocalTilingPatternCache.set - expected "name" argument.'
       );

src/core/parser.js

@@ -1115,7 +1115,6 @@ class Lexer {
       warn(`Name token is longer than allowed by the spec: ${strBuf.length}`);
     } else if (strBuf.length === 0) {
       warn("Name token is empty.");
-      return Name.empty;
     }
     return Name.get(strBuf.join(""));
   }

src/core/primitives.js

@@ -33,12 +33,6 @@ const Name = (function NameClosure() {
       return nameValue ? nameValue : (nameCache[name] = new Name(name));
     }
 
-    static get empty() {
-      // eslint-disable-next-line no-restricted-syntax
-      const emptyName = new Name({ empty: true });
-      return shadow(this, "empty", emptyName);
-    }
-
     static _clearCache() {
       nameCache = Object.create(null);
     }

test/unit/primitives_spec.js

@@ -50,6 +50,15 @@ describe("primitives", function () {
       expect(firstSubtype).toBe(secondSubtype);
       expect(firstFont).not.toBe(firstSubtype);
     });
+
+    it("should create only one object for *empty* names and cache it", function () {
+      const firstEmpty = Name.get("");
+      const secondEmpty = Name.get("");
+      const normalName = Name.get("string");
+
+      expect(firstEmpty).toBe(secondEmpty);
+      expect(firstEmpty).not.toBe(normalName);
+    });
   });
 
   describe("Cmd", function () {
@@ -491,6 +500,14 @@ describe("primitives", function () {
       expect(isName(name, "Font")).toEqual(true);
       expect(isName(name, "Subtype")).toEqual(false);
     });
+
+    it("handles *empty* names, with name check", function () {
+      const emptyName = Name.get("");
+
+      expect(isName(emptyName)).toEqual(true);
+      expect(isName(emptyName, "")).toEqual(true);
+      expect(isName(emptyName, "string")).toEqual(false);
+    });
   });
 
   describe("isCmd", function () {