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

.eslintrc

@@ -145,6 +145,10 @@
     "no-nested-ternary": "error",
     "no-new-object": "error",
     "no-restricted-syntax": ["error",
+      {
+        "selector": "CallExpression[callee.name='assert'][arguments.length!=2]",
+        "message": "`assert()` must always be invoked with two arguments.",
+      },
       {
         "selector": "NewExpression[callee.name='Cmd']",
         "message": "Use `Cmd.get()` rather than `new Cmd()`.",

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;
 }
 

test/unit/clitests_helper.js

@@ -21,8 +21,7 @@ import { setPDFNetworkStreamFactory } from "../../src/display/api.js";
 // Ensure that this script only runs in Node.js environments.
 if (!isNodeJS) {
   throw new Error(
-    "The `gulp unittestcli` command can only be used in " +
+    "The `gulp unittestcli` command can only be used in Node.js environments."
-      "Node.js environments."
   );
 }
 

test/unit/jasmine-boot.js

@@ -92,8 +92,7 @@ function initializePDFJS(callback) {
 
     if (isNodeJS) {
       throw new Error(
-        "The `gulp unittest` command cannot be used in " +
+        "The `gulp unittest` command cannot be used in Node.js environments."
-          "Node.js environments."
       );
     }
     // Set the network stream factory for unit-tests.

test/unit/node_stream_spec.js

@@ -14,12 +14,16 @@
  */
 /* globals __non_webpack_require__ */
 
-import { AbortException, assert } from "../../src/shared/util.js";
+import { AbortException } from "../../src/shared/util.js";
 import { isNodeJS } from "../../src/shared/is_node.js";
 import { PDFNodeStream } from "../../src/display/node_stream.js";
 
-// Make sure that we only running this script is Node.js environments.
+// Ensure that these test only runs in Node.js environments.
-assert(isNodeJS);
+if (!isNodeJS) {
+  throw new Error(
+    'The "node_stream" unit-tests can only be run in Node.js environments.'
+  );
+}
 
 const path = __non_webpack_require__("path");
 const url = __non_webpack_require__("url");