Bug: ask requestheaders before request body is read

Also add the beginnings of a test suite to exercise issues like this.

mitmproxy/proxy/protocol/http.py

@@ -161,10 +161,11 @@ class HttpLayer(base.Layer):
     def _process_flow(self, f):
         try:
             request = self.read_request_headers(f)
-            request.data.content = b"".join(self.read_request_body(request))
-            request.timestamp_end = time.time()
             f.request = request
             self.channel.ask("requestheaders", f)
+
+            request.data.content = b"".join(self.read_request_body(request))
+            request.timestamp_end = time.time()
             if request.headers.get("expect", "").lower() == "100-continue":
                 # TODO: We may have to use send_response_headers for HTTP2 here.
                 self.send_response(http.expect_continue_response)

test/mitmproxy/test_eventsequence.py

@@ -0,0 +1,48 @@
+from mitmproxy import events
+import contextlib
+from . import tservers
+
+
+class EAddon:
+    def __init__(self, handlers):
+        self.failure = None
+        self.handlers = handlers
+        for i in events.Events:
+            def mkprox():
+                evt = i
+
+                def prox(*args, **kwargs):
+                    if evt in self.handlers:
+                        try:
+                            handlers[evt](*args, **kwargs)
+                        except AssertionError as e:
+                            self.failure = e
+                return prox
+            setattr(self, i, mkprox())
+
+    def fail(self):
+        pass
+
+
+class SequenceTester:
+    @contextlib.contextmanager
+    def events(self, **kwargs):
+        m = EAddon(kwargs)
+        self.master.addons.add(m)
+        yield
+        self.master.addons.remove(m)
+        if m.failure:
+            raise m.failure
+
+
+class TestBasic(tservers.HTTPProxyTest, SequenceTester):
+    def test_requestheaders(self):
+
+        def req(f):
+            assert f.request.headers
+            assert not f.request.content
+
+        with self.events(requestheaders=req):
+            p = self.pathoc()
+            with p.connect():
+                assert p.request("get:'%s/p/200':b@10" % self.server.urlbase).status_code == 200