revert modify headers parameter order

docs/src/content/overview-features.md

@@ -88,17 +88,16 @@ New headers can be added, and existing headers can be overwritten or removed.
 A `modify_headers` expression looks like this:
 
 {{< highlight none  >}}
-/name/value[/filter-expression]
+[/patt]/name/value
 {{< / highlight >}}
 
-Here, **name** and **value** are the header name and the value to set respectively,
+Here, **patt** is a mitmproxy [filter expression]({{< relref "concepts-filters">}})
-e.g., ``/Host/example.org``. An empty **value** removes existing headers with
+that defines which flows to modify headers on, e.g., only on responses using ``~s``.
-**name**, e.g., ``/Host/``. The optional **filter-expression** is a mitmproxy
+The parameters **name** and **value** are the header name and the value to set
-[filter expression]({{< relref "concepts-filters">}}) that defines
+respectively, e.g., ``/Host/example.org``. An empty **value** removes existing
-which flows to modify headers on, e.g., only on responses using ``~s``.
+headers with **name**, e.g., ``/Host/``. Existing headers are overwritten by
-Existing headers are overwritten by default.
+default. This can be changed using filter-expressions, e.g., ``!~h Host:`` to
-This can be changed using filter-expressions, e.g., ``!~h Host:`` to ignore
+ignore requests and responses with an existing ``Host`` header.
-requests and responses with an existing ``Host`` header.
 
 
 ## Proxy Authentication

mitmproxy/addons/modifyheaders.py

@@ -7,23 +7,23 @@ from mitmproxy import ctx
 
 def parse_modify_headers(s):
     """
-        Returns a (header_name, header_value, flow_filter) tuple.
+        Returns a (flow_filter, header_name, header_value) tuple.
 
         The general form for a modify_headers hook is as follows:
 
-            /header_name/header_value/flow_filter
+            [/flow_filter]/header_name/header_value
 
         The first character specifies the separator. Example:
 
-            :foo:bar:~q
+            :~q:foo:bar
 
         If only two clauses are specified, the pattern is set to match
         universally (i.e. ".*"). Example:
 
-            /foo/bar/
+            /foo/bar
 
         Clauses are parsed from left to right. Extra separators are taken to be
-        part of the final clause. For instance, the flow filter below is
+        part of the final clause. For instance, the replacement clause below is
         "foo/bar/":
 
             /one/two/foo/bar/
@@ -34,12 +34,12 @@ def parse_modify_headers(s):
         flow_filter = ".*"
         header_name, header_value = parts
     elif len(parts) == 3:
-        header_name, header_value, flow_filter = parts
+        flow_filter, header_name, header_value = parts
     else:
         raise exceptions.OptionsError(
-            "Invalid replacement specifier: %s" % s
+            "Invalid modify_headers specifier: %s" % s
         )
-    return header_name, header_value, flow_filter
+    return flow_filter, header_name, header_value
 
 
 class ModifyHeaders:
@@ -50,7 +50,7 @@ class ModifyHeaders:
         loader.add_option(
             "modify_headers", typing.Sequence[str], [],
             """
-            Header modify pattern of the form "/header-name/header-value[/flow-filter]", where the
+            Header modify pattern of the form "[/flow-filter]/header-name/header-value", where the
             separator can be any character. An empty header-value removes existing header-name headers.
             """
         )
@@ -59,20 +59,20 @@ class ModifyHeaders:
         if "modify_headers" in updated:
             self.lst = []
             for shead in ctx.options.modify_headers:
-                header, value, flow_pattern = parse_modify_headers(shead)
+                flow_pattern, header, value = parse_modify_headers(shead)
 
                 flow_filter = flowfilter.parse(flow_pattern)
                 if not flow_filter:
                     raise exceptions.OptionsError(
                         "Invalid modify_headers flow filter %s" % flow_pattern
                     )
-                self.lst.append((header, value, flow_pattern, flow_filter))
+                self.lst.append((flow_pattern, flow_filter, header, value))
 
     def run(self, f, hdrs):
-        for header, value, _, flow_filter in self.lst:
+        for _, flow_filter, header, value in self.lst:
             if flow_filter(f):
                 hdrs.pop(header, None)
-        for header, value, _, flow_filter in self.lst:
+        for _, flow_filter, header, value in self.lst:
             if flow_filter(f) and value:
                 hdrs.add(header, value)
 

test/mitmproxy/addons/test_modifyheaders.py

@@ -13,15 +13,15 @@ class TestModifyHeaders:
         x = modifyheaders.parse_modify_headers("/foo/bar/vo/ing/")
         assert x == ("foo", "bar", "vo/ing/")
         x = modifyheaders.parse_modify_headers("/bar/voing")
-        assert x == ("bar", "voing", ".*")
+        assert x == (".*", "bar", "voing")
-        with pytest.raises(Exception, match="Invalid replacement"):
+        with pytest.raises(Exception, match="Invalid modify_headers specifier"):
             modifyheaders.parse_modify_headers("/")
 
     def test_configure(self):
         sh = modifyheaders.ModifyHeaders()
         with taddons.context(sh) as tctx:
             with pytest.raises(Exception, match="Invalid modify_headers flow filter"):
-                tctx.configure(sh, modify_headers = ["/one/two/~b"])
+                tctx.configure(sh, modify_headers = ["/~b/one/two"])
             tctx.configure(sh, modify_headers = ["/foo/bar/voing"])
 
     def test_modify_headers(self):
@@ -30,8 +30,8 @@ class TestModifyHeaders:
             tctx.configure(
                 sh,
                 modify_headers = [
-                    "/one/two/~q",
+                    "/~q/one/two",
-                    "/one/three/~s"
+                    "/~s/one/three"
                 ]
             )
             f = tflow.tflow()
@@ -47,8 +47,8 @@ class TestModifyHeaders:
             tctx.configure(
                 sh,
                 modify_headers = [
-                    "/one/two/~s",
+                    "/~s/one/two",
-                    "/one/three/~s"
+                    "/~s/one/three"
                 ]
             )
             f = tflow.tflow(resp=True)
@@ -60,8 +60,8 @@ class TestModifyHeaders:
             tctx.configure(
                 sh,
                 modify_headers = [
-                    "/one/two/~q",
+                    "/~q/one/two",
-                    "/one/three/~q"
+                    "/~q/one/three"
                 ]
             )
             f = tflow.tflow()
@@ -73,8 +73,8 @@ class TestModifyHeaders:
             tctx.configure(
                 sh,
                 modify_headers = [
-                    "/one//~q",
+                    "/~q/one/",
-                    "/one//~s"
+                    "/~s/one/"
                 ]
             )
             f = tflow.tflow()