Bug 1657445 - [wptserve] Content-Length header missing when response is a file object r=jgraham

Differential Revision: https://phabricator.services.mozilla.com/D86052

testing/web-platform/tests/tools/wptserve/wptserve/response.py

@@ -2,6 +2,7 @@ from collections import OrderedDict
 from datetime import datetime, timedelta
 from io import BytesIO
 import json
+import os
 import socket
 import uuid
 
@@ -711,10 +712,15 @@ class ResponseWriter(object):
             if not self._seen_header(name):
                 self.write_header(name, f())
 
-        if (isinstance(self._response.content, (binary_type, text_type)) and
-            not self._seen_header("content-length")):
-            #Would be nice to avoid double-encoding here
-            self.write_header("Content-Length", len(self.encode(self._response.content)))
+        if not self._seen_header("content-length"):
+            content_length = None
+            if isinstance(self._response.content, (binary_type, text_type)):
+                #Would be nice to avoid double-encoding here
+                content_length = len(self.encode(self._response.content))
+            elif isinstance(self._response.content, file):
+                content_length = os.fstat(self._response.content.fileno()).st_size
+            if content_length:
+                self.write_header("Content-Length", content_length)
 
     def end_headers(self):
         """Finish writing headers and write the separator.