Merge pull request #19895 from Snuffleupagus/ObjectLoader-improve

Unify method return values in the `ObjectLoader` class, and simplify how the `ObjectLoader` is used

Author: Snuffleupagus

eslint.config.mjs

@@ -303,6 +303,11 @@ export default [
           selector: "NewExpression[callee.name='Name']",
           message: "Use `Name.get()` rather than `new Name()`.",
         },
+        {
+          selector: "NewExpression[callee.name='ObjectLoader']",
+          message:
+            "Use `ObjectLoader.load()` rather than `new ObjectLoader()`.",
+        },
         {
           selector: "NewExpression[callee.name='Ref']",
           message: "Use `Ref.get()` rather than `new Ref()`.",

src/core/annotation.js

@@ -1158,15 +1158,12 @@ class Annotation {
     }
   }
 
-  loadResources(keys, appearance) {
-    return appearance.dict.getAsync("Resources").then(resources => {
-      if (!resources) {
-        return undefined;
-      }
-
-      const objectLoader = new ObjectLoader(resources, keys, resources.xref);
-      return objectLoader.load().then(() => resources);
-    });
+  async loadResources(keys, appearance) {
+    const resources = await appearance.dict.getAsync("Resources");
+    if (resources) {
+      await ObjectLoader.load(resources, keys, resources.xref);
+    }
+    return resources;
   }
 
   async getOperatorList(evaluator, task, intent, annotationStorage) {

src/core/document.js

@@ -417,8 +417,7 @@ class Page {
     // TODO: add async `_getInheritableProperty` and remove this.
     await (this.resourcesPromise ??= this.pdfManager.ensure(this, "resources"));
 
-    const objectLoader = new ObjectLoader(this.resources, keys, this.xref);
-    await objectLoader.load();
+    await ObjectLoader.load(this.resources, keys, this.xref);
   }
 
   async #getMergedResources(streamDict, keys) {
@@ -430,8 +429,7 @@ class Page {
     if (!(localResources instanceof Dict && localResources.size)) {
       return this.resources;
     }
-    const objectLoader = new ObjectLoader(localResources, keys, this.xref);
-    await objectLoader.load();
+    await ObjectLoader.load(localResources, keys, this.xref);
 
     return Dict.merge({
       xref: this.xref,
@@ -1254,8 +1252,7 @@ class PDFDocument {
     if (!(resources instanceof Dict)) {
       return;
     }
-    const objectLoader = new ObjectLoader(resources, ["Font"], this.xref);
-    await objectLoader.load();
+    await ObjectLoader.load(resources, ["Font"], this.xref);
 
     const fontRes = resources.get("Font");
     if (!(fontRes instanceof Dict)) {

src/core/object_loader.js

@@ -54,21 +54,16 @@ function addChildren(node, nodesToVisit) {
  * entire PDF document object graph to be traversed.
  */
 class ObjectLoader {
+  refSet = new RefSet();
+
   constructor(dict, keys, xref) {
     this.dict = dict;
     this.keys = keys;
     this.xref = xref;
-    this.refSet = null;
   }
 
   async load() {
-    // Don't walk the graph if all the data is already loaded.
-    if (this.xref.stream.isDataLoaded) {
-      return undefined;
-    }
-
     const { keys, dict } = this;
-    this.refSet = new RefSet();
     // Setup the initial nodes to visit.
     const nodesToVisit = [];
     for (const key of keys) {
@@ -78,10 +73,12 @@ class ObjectLoader {
         nodesToVisit.push(rawValue);
       }
     }
-    return this._walk(nodesToVisit);
+    await this.#walk(nodesToVisit);
+
+    this.refSet = null; // Everything is loaded, clear the cache.
   }
 
-  async _walk(nodesToVisit) {
+  async #walk(nodesToVisit) {
     const nodesToRevisit = [];
     const pendingRequests = [];
     // DFS walk of the object graph.
@@ -99,11 +96,10 @@ class ObjectLoader {
           currentNode = this.xref.fetch(currentNode);
         } catch (ex) {
           if (!(ex instanceof MissingDataException)) {
-            warn(`ObjectLoader._walk - requesting all data: "${ex}".`);
-            this.refSet = null;
+            warn(`ObjectLoader.#walk - requesting all data: "${ex}".`);
 
-            const { manager } = this.xref.stream;
-            return manager.requestAllChunks();
+            await this.xref.stream.manager.requestAllChunks();
+            return;
           }
           nodesToRevisit.push(currentNode);
           pendingRequests.push({ begin: ex.begin, end: ex.end });
@@ -139,11 +135,18 @@ class ObjectLoader {
           this.refSet.remove(node);
         }
       }
-      return this._walk(nodesToRevisit);
+      await this.#walk(nodesToRevisit);
+    }
+  }
+
+  static async load(obj, keys, xref) {
+    // Don't walk the graph if all the data is already loaded.
+    if (xref.stream.isDataLoaded) {
+      return;
     }
-    // Everything is loaded.
-    this.refSet = null;
-    return undefined;
+    // eslint-disable-next-line no-restricted-syntax
+    const objLoader = new ObjectLoader(obj, keys, xref);
+    await objLoader.load();
   }
 }