Use the ESLint no-restricted-syntax rule to ensure that assert is always called with two arguments

Having `assert` calls without a message string isn't very helpful when debugging, and it turns out that it's easy enough to make use of ESLint to enforce better `assert` call-sites.
In a couple of cases the `assert` calls were changed to "regular" throwing of errors instead, since that seemed more appropriate.

Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-restricted-syntax

src/core/document.js

@@ -767,7 +767,15 @@ class PDFDocument {
 
   _getLinearizationPage(pageIndex) {
     const { catalog, linearization } = this;
-    assert(linearization && linearization.pageFirst === pageIndex);
+    if (
+      typeof PDFJSDev === "undefined" ||
+      PDFJSDev.test("!PRODUCTION || TESTING")
+    ) {
+      assert(
+        linearization && linearization.pageFirst === pageIndex,
+        "_getLinearizationPage - invalid pageIndex argument."
+      );
+    }
 
     const ref = Ref.get(linearization.objectNumberFirst, 0);
     return this.xref

src/core/obj.js

@@ -578,7 +578,11 @@ class Catalog {
             }
             break;
           default:
-            assert(typeof value === "boolean");
+            if (typeof value !== "boolean") {
+              throw new FormatError(
+                `viewerPreferences - expected a boolean value for: ${key}`
+              );
+            }
             prefValue = value;
         }
 

src/core/parser.js

@@ -216,7 +216,7 @@ class Parser {
       } else if (state === 1) {
         state = ch === I ? 2 : 0;
       } else {
-        assert(state === 2);
+        assert(state === 2, "findDefaultInlineStreamEnd - invalid state.");
         if (ch === SPACE || ch === LF || ch === CR) {
           maybeEIPos = stream.pos;
           // Let's check that the next `n` bytes are ASCII... just to be sure.

src/core/worker_stream.js

@@ -26,7 +26,10 @@ class PDFWorkerStream {
   }
 
   getFullReader() {
-    assert(!this._fullRequestReader);
+    assert(
+      !this._fullRequestReader,
+      "PDFWorkerStream.getFullReader can only be called once."
+    );
     this._fullRequestReader = new PDFWorkerStreamReader(this._msgHandler);
     return this._fullRequestReader;
   }

src/display/api.js

@@ -2023,7 +2023,10 @@ class WorkerTransport {
     const { messageHandler, loadingTask } = this;
 
     messageHandler.on("GetReader", (data, sink) => {
-      assert(this._networkStream);
+      assert(
+        this._networkStream,
+        "GetReader - no `IPDFStream` instance available."
+      );
       this._fullReader = this._networkStream.getFullReader();
       this._fullReader.onProgress = evt => {
         this._lastProgress = {
@@ -2039,7 +2042,10 @@ class WorkerTransport {
               sink.close();
               return;
             }
-            assert(isArrayBuffer(value));
+            assert(
+              isArrayBuffer(value),
+              "GetReader - expected an ArrayBuffer."
+            );
             // Enqueue data chunk into sink, and transfer it
             // to other side as `Transferable` object.
             sink.enqueue(new Uint8Array(value), 1, [value]);
@@ -2085,7 +2091,10 @@ class WorkerTransport {
     });
 
     messageHandler.on("GetRangeReader", (data, sink) => {
-      assert(this._networkStream);
+      assert(
+        this._networkStream,
+        "GetRangeReader - no `IPDFStream` instance available."
+      );
       const rangeReader = this._networkStream.getRangeReader(
         data.begin,
         data.end
@@ -2114,7 +2123,10 @@ class WorkerTransport {
               sink.close();
               return;
             }
-            assert(isArrayBuffer(value));
+            assert(
+              isArrayBuffer(value),
+              "GetRangeReader - expected an ArrayBuffer."
+            );
             sink.enqueue(new Uint8Array(value), 1, [value]);
           })
           .catch(reason => {

src/display/fetch_stream.js

@@ -65,7 +65,10 @@ class PDFFetchStream {
   }
 
   getFullReader() {
-    assert(!this._fullRequestReader);
+    assert(
+      !this._fullRequestReader,
+      "PDFFetchStream.getFullReader can only be called once."
+    );
     this._fullRequestReader = new PDFFetchStreamReader(this);
     return this._fullRequestReader;
   }

src/display/network.js

@@ -247,7 +247,10 @@ class PDFNetworkStream {
   }
 
   getFullReader() {
-    assert(!this._fullRequestReader);
+    assert(
+      !this._fullRequestReader,
+      "PDFNetworkStream.getFullReader can only be called once."
+    );
     this._fullRequestReader = new PDFNetworkStreamFullRequestReader(
       this._manager,
       this._source

src/display/node_stream.js

@@ -67,7 +67,10 @@ class PDFNodeStream {
   }
 
   getFullReader() {
-    assert(!this._fullRequestReader);
+    assert(
+      !this._fullRequestReader,
+      "PDFNodeStream.getFullReader can only be called once."
+    );
     this._fullRequestReader = this.isFsUrl
       ? new PDFNodeStreamFsFullReader(this)
       : new PDFNodeStreamFullReader(this);

src/display/transport_stream.js

@@ -19,7 +19,10 @@ import { assert, createPromiseCapability } from "../shared/util.js";
 /** @implements {IPDFStream} */
 class PDFDataTransportStream {
   constructor(params, pdfDataRangeTransport) {
-    assert(pdfDataRangeTransport);
+    assert(
+      pdfDataRangeTransport,
+      'PDFDataTransportStream - missing required "pdfDataRangeTransport" argument.'
+    );
 
     this._queuedChunks = [];
     this._progressiveDone = params.progressiveDone || false;
@@ -73,7 +76,10 @@ class PDFDataTransportStream {
         rangeReader._enqueue(buffer);
         return true;
       });
-      assert(found);
+      assert(
+        found,
+        "_onReceiveData - no `PDFDataTransportStreamRangeReader` instance found."
+      );
     }
   }
 
@@ -111,7 +117,10 @@ class PDFDataTransportStream {
   }
 
   getFullReader() {
-    assert(!this._fullRequestReader);
+    assert(
+      !this._fullRequestReader,
+      "PDFDataTransportStream.getFullReader can only be called once."
+    );
     const queuedChunks = this._queuedChunks;
     this._queuedChunks = null;
     return new PDFDataTransportStreamReader(

src/shared/util.js

@@ -516,7 +516,7 @@ function arrayByteLength(arr) {
   if (arr.length !== undefined) {
     return arr.length;
   }
-  assert(arr.byteLength !== undefined);
+  assert(arr.byteLength !== undefined, "arrayByteLength - invalid argument.");
   return arr.byteLength;
 }