fs: fix options.end of fs.ReadStream()

Fixes: nodejs#18116
PR-URL: nodejs#18121
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>

Author: 陈刚

lib/fs.js

@@ -1942,7 +1942,8 @@ function ReadStream(path, options) {
   this.flags = options.flags === undefined ? 'r' : options.flags;
   this.mode = options.mode === undefined ? 0o666 : options.mode;
 
-  this.start = options.start;
+  this.start = typeof this.fd !== 'number' && options.start === undefined ?
+    0 : options.start;
   this.end = options.end;
   this.autoClose = options.autoClose === undefined ? true : options.autoClose;
   this.pos = undefined;

test/parallel/test-fs-read-stream.js

@@ -157,6 +157,20 @@ assert.throws(function() {
   }));
 }
 
+{
+  // Verify that end works when start is not specified.
+  const stream = new fs.createReadStream(rangeFile, { end: 1 });
+  stream.data = '';
+
+  stream.on('data', function(chunk) {
+    stream.data += chunk;
+  });
+
+  stream.on('end', common.mustCall(function() {
+    assert.strictEqual('xy', stream.data);
+  }));
+}
+
 {
   // pause and then resume immediately.
   const pauseRes = fs.createReadStream(rangeFile);