In Node.js, don't abort the full request for local PDF files smaller than two range requests

This follows the behaviour used with both the Fetch API and `XMLHttpRequest`, compare with the `validateRangeRequestCapabilities` helper function.

Author: Snuffleupagus

src/display/node_stream.js

@@ -104,8 +104,14 @@ class PDFNodeStreamFsFullReader {
     const fs = process.getBuiltinModule("fs");
     fs.promises.lstat(this._url).then(
       stat => {
+        const { size } = stat;
+        if (size <= 2 * this._rangeChunkSize) {
+          // The file size is smaller than the size of two chunks, so it doesn't
+          // make any sense to abort the request and retry with a range request.
+          this._isRangeSupported = false;
+        }
         // Setting right content length.
-        this._contentLength = stat.size;
+        this._contentLength = size;
 
         this._setReadableStream(fs.createReadStream(this._url));
         this._headersCapability.resolve();

test/unit/node_stream_spec.js

@@ -117,4 +117,41 @@ describe("node_stream", function () {
     expect(isRangeSupported).toEqual(true);
     expect(fullReaderCancelled).toEqual(true);
   });
+
+  it("read filesystem pdf files (smaller than two range requests)", async function () {
+    const smallPdf = new URL("./test/pdfs/empty.pdf", cwdURL).href;
+    const smallLength = 4920;
+
+    const stream = new PDFNodeStream({
+      url: smallPdf,
+      rangeChunkSize: 65536,
+      disableStream: true,
+      disableRange: false,
+    });
+
+    const fullReader = stream.getFullReader();
+
+    let isStreamingSupported, isRangeSupported;
+    const promise = fullReader.headersReady.then(() => {
+      isStreamingSupported = fullReader.isStreamingSupported;
+      isRangeSupported = fullReader.isRangeSupported;
+    });
+
+    let len = 0;
+    const read = function () {
+      return fullReader.read().then(function (result) {
+        if (result.done) {
+          return undefined;
+        }
+        len += result.value.byteLength;
+        return read();
+      });
+    };
+
+    await Promise.all([read(), promise]);
+
+    expect(isStreamingSupported).toEqual(false);
+    expect(isRangeSupported).toEqual(false);
+    expect(len).toEqual(smallLength);
+  });
 });