Add more logical assignment in the src/ folder

This patch uses nullish coalescing assignment in cases where it's immediately obvious from surrounding code that doing so is safe, and logical OR assignment elsewhere (mostly the changes in XFA code).

Author: Snuffleupagus

src/core/annotation.js

@@ -3488,8 +3488,8 @@ class ChoiceWidgetAnnotation extends WidgetAnnotation {
       // always make the field value an array with zero, one or multiple items.
       if (typeof this.data.fieldValue === "string") {
         this.data.fieldValue = [this.data.fieldValue];
-      } else if (!this.data.fieldValue) {
-        this.data.fieldValue = [];
+      } else {
+        this.data.fieldValue ||= [];
       }
     } else {
       // The specs say that we should have an indices array only with

src/core/catalog.js

@@ -998,9 +998,7 @@ class Catalog {
         warn(`Bad value, for key "${key}", in ViewerPreferences: ${value}.`);
         continue;
       }
-      if (!prefs) {
-        prefs = Object.create(null);
-      }
+      prefs ??= Object.create(null);
       prefs[key] = prefValue;
     }
     return shadow(this, "viewerPreferences", prefs);
@@ -1042,9 +1040,7 @@ class Catalog {
       const nameTree = new NameTree(obj.getRaw("EmbeddedFiles"), this.xref);
       for (const [key, value] of nameTree.getAll()) {
         const fs = new FileSpec(value, this.xref);
-        if (!attachments) {
-          attachments = Object.create(null);
-        }
+        attachments ??= Object.create(null);
         attachments[stringToPDFString(key)] = fs.serializable;
       }
     }
@@ -1058,9 +1054,7 @@ class Catalog {
     if (obj instanceof Dict && obj.has("XFAImages")) {
       const nameTree = new NameTree(obj.getRaw("XFAImages"), this.xref);
       for (const [key, value] of nameTree.getAll()) {
-        if (!xfaImages) {
-          xfaImages = new Dict(this.xref);
-        }
+        xfaImages ??= new Dict(this.xref);
         xfaImages.set(stringToPDFString(key), value);
       }
     }

src/core/document.js

@@ -1532,9 +1532,7 @@ class PDFDocument {
             warn(`Bad value, for custom key "${key}", in Info: ${value}.`);
             continue;
           }
-          if (!docInfo.Custom) {
-            docInfo.Custom = Object.create(null);
-          }
+          docInfo.Custom ??= Object.create(null);
           docInfo.Custom[key] = customValue;
           continue;
       }

src/core/xfa/parser.js

@@ -91,9 +91,7 @@ class XFAParser extends XMLParserBase {
         }
       } else if (name.startsWith("xmlns:")) {
         const prefix = name.substring("xmlns:".length);
-        if (!prefixes) {
-          prefixes = [];
-        }
+        prefixes ??= [];
         prefixes.push({ prefix, value });
       } else {
         const i = name.indexOf(":");
@@ -102,10 +100,7 @@ class XFAParser extends XMLParserBase {
         } else {
           // Attributes can have their own namespace.
           // For example in data, we can have <foo xfa:dataNode="dataGroup"/>
-          let nsAttrs = attributeObj[$nsAttributes];
-          if (!nsAttrs) {
-            nsAttrs = attributeObj[$nsAttributes] = Object.create(null);
-          }
+          const nsAttrs = (attributeObj[$nsAttributes] ??= Object.create(null));
           const [ns, attrName] = [name.slice(0, i), name.slice(i + 1)];
           const attrs = (nsAttrs[ns] ||= Object.create(null));
           attrs[attrName] = value;

src/core/xfa/template.js

@@ -2462,9 +2462,7 @@ class ExclGroup extends XFAObject {
 
     setAccess(this, attributes.class);
 
-    if (!this[$extra]) {
-      this[$extra] = Object.create(null);
-    }
+    this[$extra] ||= Object.create(null);
 
     Object.assign(this[$extra], {
       children,
@@ -2953,9 +2951,7 @@ class Field extends XFAObject {
       }
     }
 
-    if (!ui.attributes.style) {
-      ui.attributes.style = Object.create(null);
-    }
+    ui.attributes.style ||= Object.create(null);
 
     let aElement = null;
 
@@ -3048,9 +3044,7 @@ class Field extends XFAObject {
       caption.attributes.class[0] = "xfaCaptionForCheckButton";
     }
 
-    if (!ui.attributes.class) {
-      ui.attributes.class = [];
-    }
+    ui.attributes.class ||= [];
 
     ui.children.splice(0, 0, caption);
 
@@ -4067,11 +4061,9 @@ class PageArea extends XFAObject {
   }
 
   [$getNextPage]() {
-    if (!this[$extra]) {
-      this[$extra] = {
-        numberOfUse: 0,
-      };
-    }
+    this[$extra] ||= {
+      numberOfUse: 0,
+    };
 
     const parent = this[$getParent]();
     if (parent.relation === "orderedOccurrence") {
@@ -4090,11 +4082,9 @@ class PageArea extends XFAObject {
 
   [$toHTML]() {
     // TODO: incomplete.
-    if (!this[$extra]) {
-      this[$extra] = {
-        numberOfUse: 1,
-      };
-    }
+    this[$extra] ||= {
+      numberOfUse: 1,
+    };
 
     const children = [];
     this[$extra].children = children;
@@ -4186,13 +4176,11 @@ class PageSet extends XFAObject {
   }
 
   [$getNextPage]() {
-    if (!this[$extra]) {
-      this[$extra] = {
-        numberOfUse: 1,
-        pageIndex: -1,
-        pageSetIndex: -1,
-      };
-    }
+    this[$extra] ||= {
+      numberOfUse: 1,
+      pageIndex: -1,
+      pageSetIndex: -1,
+    };
 
     if (this.relation === "orderedOccurrence") {
       if (this[$extra].pageIndex + 1 < this.pageArea.children.length) {
@@ -5067,9 +5055,7 @@ class Subform extends XFAObject {
 
     setAccess(this, attributes.class);
 
-    if (!this[$extra]) {
-      this[$extra] = Object.create(null);
-    }
+    this[$extra] ||= Object.create(null);
 
     Object.assign(this[$extra], {
       children,
@@ -5495,9 +5481,7 @@ class Template extends XFAObject {
       }
     }
 
-    if (!pageArea) {
-      pageArea = pageAreas[0];
-    }
+    pageArea ||= pageAreas[0];
 
     pageArea[$extra] = {
       numberOfUse: 1,

src/scripting_api/app.js

@@ -202,18 +202,15 @@ class App extends PDFObject {
   }
 
   get constants() {
-    if (!this._constants) {
-      this._constants = Object.freeze({
-        align: Object.freeze({
-          left: 0,
-          center: 1,
-          right: 2,
-          top: 3,
-          bottom: 4,
-        }),
-      });
-    }
-    return this._constants;
+    return (this._constants ??= Object.freeze({
+      align: Object.freeze({
+        left: 0,
+        center: 1,
+        right: 2,
+        top: 3,
+        bottom: 4,
+      }),
+    }));
   }
 
   set constants(_) {