Account for buffered data when determining whether a readable has bee…

…n read (parcel-bundler#3817)

* Account for read stream buffering when determining read streams

* Add test for large assets

packages/core/core/src/InternalAsset.js

@@ -127,7 +127,9 @@ export default class InternalAsset {
     if (
       // $FlowFixMe
       typeof contentStream.bytesRead === 'number' &&
-      contentStream.bytesRead > 0
+      // If the amount of data read from this stream so far isn't exactly the amount
+      // of data that is available to be read, then it has been read from.
+      contentStream.bytesRead !== contentStream.readableLength
     ) {
       throw new Error(
         'Stream has already been read. This may happen if a plugin reads from a stream and does not replace it.'

packages/core/integration-tests/test/javascript.js

@@ -5,6 +5,8 @@ import {
   bundler,
   run,
   assertBundles,
+  ncp,
+  overlayFS,
   removeDistDirectory,
   distDir,
   outputFS,
@@ -797,6 +799,40 @@ describe('javascript', function() {
     assert.equal(stats.size, 9);
   });
 
+  it('should support importing a URL to a large raw asset', async function() {
+    // 6 megabytes, which exceeds the threshold in summarizeRequest for buffering
+    // entire contents into memory and should stream content instead
+    let assetSizeBytes = 6000000;
+
+    let distDir = '/dist';
+    let fixtureDir = path.join(__dirname, '/integration/import-raw');
+    let inputDir = path.join(__dirname, 'input');
+
+    await ncp(fixtureDir, inputDir);
+    await outputFS.writeFile(
+      path.join(inputDir, 'test.txt'),
+      Buffer.alloc(assetSizeBytes)
+    );
+
+    let b = await bundle(path.join(inputDir, 'index.js'), {inputFS: overlayFS});
+    assertBundles(b, [
+      {
+        name: 'index.js',
+        assets: ['index.js', 'test.txt.js']
+      },
+      {
+        type: 'txt',
+        assets: ['test.txt']
+      }
+    ]);
+
+    let output = await run(b);
+    assert.equal(typeof output, 'function');
+    assert(/^\/test\.[0-9a-f]+\.txt$/.test(output()));
+    let stats = await outputFS.stat(path.join(distDir, output()));
+    assert.equal(stats.size, assetSizeBytes);
+  });
+
   it('should minify JS in production mode', async function() {
     let b = await bundle(path.join(__dirname, '/integration/uglify/index.js'), {
       minify: true,