Make sure session and default headers play nice

Before: headers = default + args + session
Now:    headers = default + session + args

Fixes #180

README.rst

@@ -1246,6 +1246,7 @@ Changelog
     * Added ``--cert`` and ``--certkey`` parameters to specify a client side
       certificate and private key for SSL
     * Improved unicode support.
+    * Fixed ``User-Agent`` overwriting when used within a session.
     * Switched from ``unittest`` to ``pytest``.
     * Various test suite improvements.
     * Added `CONTRIBUTING`_.

httpie/client.py

@@ -18,26 +18,27 @@
 def get_response(args, config_dir):
     """Send the request and return a `request.Response`."""
 
-    requests_kwargs = get_requests_kwargs(args)
-
-    if args.debug:
-        sys.stderr.write('\n>>> requests.request(%s)\n\n'
-                         % pformat(requests_kwargs))
-
     if not args.session and not args.session_read_only:
+        requests_kwargs = get_requests_kwargs(args)
+        if args.debug:
+            dump_request(requests_kwargs)
         response = requests.request(**requests_kwargs)
     else:
         response = sessions.get_response(
             args=args,
             config_dir=config_dir,
             session_name=args.session or args.session_read_only,
-            requests_kwargs=requests_kwargs,
             read_only=bool(args.session_read_only),
         )
 
     return response
 
 
+def dump_request(kwargs):
+    sys.stderr.write('\n>>> requests.request(%s)\n\n'
+                     % pformat(kwargs))
+
+
 def encode_headers(headers):
     # This allows for unicode headers which is non-standard but practical.
     # See: https://github.com/jakubroztocil/httpie/issues/212
@@ -47,36 +48,47 @@ def encode_headers(headers):
     )
 
 
-def get_requests_kwargs(args):
-    """Translate our `args` into `requests.request` keyword arguments."""
-
-    implicit_headers = {
+def get_default_headers(args):
+    default_headers = {
         'User-Agent': DEFAULT_UA
     }
 
     auto_json = args.data and not args.form
     # FIXME: Accept is set to JSON with `http url @./file.txt`.
     if args.json or auto_json:
-        implicit_headers['Accept'] = 'application/json'
+        default_headers['Accept'] = 'application/json'
         if args.json or (auto_json and args.data):
-            implicit_headers['Content-Type'] = JSON
-
-        if isinstance(args.data, dict):
-            if args.data:
-                args.data = json.dumps(args.data)
-            else:
-                # We need to set data to an empty string to prevent requests
-                # from assigning an empty list to `response.request.data`.
-                args.data = ''
+            default_headers['Content-Type'] = JSON
 
     elif args.form and not args.files:
         # If sending files, `requests` will set
         # the `Content-Type` for us.
-        implicit_headers['Content-Type'] = FORM
-
-    for name, value in implicit_headers.items():
-        if name not in args.headers:
-            args.headers[name] = value
+        default_headers['Content-Type'] = FORM
+    return default_headers
+
+
+def get_requests_kwargs(args, base_headers=None):
+    """
+    Translate our `args` into `requests.request` keyword arguments.
+
+    """
+    # Serialize JSON data, if needed.
+    data = args.data
+    auto_json = data and not args.form
+    if args.json or auto_json and isinstance(data, dict):
+        if data:
+            data = json.dumps(data)
+        else:
+            # We need to set data to an empty string to prevent requests
+            # from assigning an empty list to `response.request.data`.
+            data = ''
+
+    # Finalize headers.
+    headers = get_default_headers(args)
+    if base_headers:
+        headers.update(base_headers)
+    headers.update(args.headers)
+    headers = encode_headers(headers)
 
     credentials = None
     if args.auth:
@@ -87,14 +99,14 @@ def get_requests_kwargs(args):
     if args.cert:
         cert = args.cert
         if args.certkey:
-            cert = (cert, args.certkey)
+            cert = cert, args.certkey
 
     kwargs = {
         'stream': True,
         'method': args.method.lower(),
         'url': args.url,
-        'headers': encode_headers(args.headers),
-        'data': args.data,
+        'headers': headers,
+        'data': data,
         'verify': {
             'yes': True,
             'no': False

httpie/sessions.py

@@ -21,21 +21,17 @@
 SESSION_IGNORED_HEADER_PREFIXES = ['Content-', 'If-']
 
 
-def get_response(session_name, requests_kwargs, config_dir, args,
-                 read_only=False):
+def get_response(session_name, config_dir, args, read_only=False):
     """Like `client.get_response`, but applies permanent
     aspects of the session to the request.
 
     """
-    from .client import encode_headers
+    from .client import get_requests_kwargs, dump_request
     if os.path.sep in session_name:
         path = os.path.expanduser(session_name)
     else:
-        hostname = (
-            requests_kwargs['headers'].get('Host', None)
-            or urlsplit(requests_kwargs['url']).netloc.split('@')[-1]
-        )
-
+        hostname = (args.headers.get('Host', None)
+                    or urlsplit(args.url).netloc.split('@')[-1])
         assert re.match('^[a-zA-Z0-9_.:-]+$', hostname)
 
         # host:port => host_port
@@ -48,13 +44,10 @@ def get_response(session_name, requests_kwargs, config_dir, args,
     session = Session(path)
     session.load()
 
-    request_headers = requests_kwargs.get('headers', {})
-
-    merged_headers = dict(session.headers)
-    merged_headers.update(request_headers)
-    requests_kwargs['headers'] = encode_headers(merged_headers)
-
-    session.update_headers(request_headers)
+    requests_kwargs = get_requests_kwargs(args, base_headers=session.headers)
+    if args.debug:
+        dump_request(requests_kwargs)
+    session.update_headers(requests_kwargs['headers'])
 
     if args.auth:
         session.auth = {

tests/test_sessions.py

@@ -137,3 +137,14 @@ def test_session_unicode(self):
         assert (r2.json['headers']['Authorization']
                 == HTTPBasicAuth.make_header(u'test', UNICODE))
         assert r2.json['headers']['Test'] == UNICODE
+
+    def test_session_default_header_value_overwritten(self):
+        # https://github.com/jakubroztocil/httpie/issues/180
+        r1 = http('--session=test', httpbin('/headers'), 'User-Agent:custom',
+                  env=self.env())
+        assert HTTP_OK in r1
+        assert r1.json['headers']['User-Agent'] == 'custom'
+
+        r2 = http('--session=test', httpbin('/headers'), env=self.env())
+        assert HTTP_OK in r2
+        assert r2.json['headers']['User-Agent'] == 'custom'