Add option to control stripping newlines from edited bodies (mitmprox…

…y#4125)

CHANGELOG

@@ -6,6 +6,7 @@ Unreleased: mitmproxy next
     * Use `@charset` to decode CSS files if available (@prinzhorn)
     * Fix links to anticache docs in mitmweb and use HTTPS for links to documentation (@rugk)
     * Updated typing for WebsocketMessage.content (@prinzhorn)
+    * Add option `console_strip_trailing_newlines`, and no longer strip trailing newlines by default (@capt8bit)
     * Prevent transparent mode from connecting to itself in the basic cases (@prinzhorn)
     * Display HTTP trailers in mitmweb (@sanlengjingvv)
     * Revamp onboarding app (@mhils)

mitmproxy/tools/console/consoleaddons.py

@@ -120,13 +120,16 @@ def load(self, loader):
             "console_mouse", bool, True,
             "Console mouse interaction."
         )
-
         loader.add_option(
             "console_flowlist_layout",
             str, "default",
             "Set the flowlist layout",
             choices=sorted(console_flowlist_layout)
         )
+        loader.add_option(
+            "console_strip_trailing_newlines", bool, False,
+            "Strip trailing newlines from edited request/response bodies."
+        )
 
     @command.command("console.layout.options")
     def layout_options(self) -> typing.Sequence[str]:
@@ -449,13 +452,14 @@ def edit_focus(self, flow_part: str) -> None:
             else:
                 message = flow.response
             c = self.master.spawn_editor(message.get_content(strict=False) or b"")
-            # Fix an issue caused by some editors when editing a
-            # request/response body. Many editors make it hard to save a
-            # file without a terminating newline on the last line. When
-            # editing message bodies, this can cause problems. For now, I
-            # just strip the newlines off the end of the body when we return
-            # from an editor.
-            message.content = c.rstrip(b"\n")
+            # Many editors make it hard to save a file without a terminating
+            # newline on the last line. When editing message bodies, this can
+            # cause problems. We strip trailing newlines by default, but this
+            # behavior is configurable.
+            if self.master.options.console_strip_trailing_newlines:
+                message.content = c.rstrip(b"\n")
+            else:
+                message.content = c
         elif flow_part == "set-cookies":
             self.master.switch_view("edit_focus_setcookies")
         elif flow_part == "url":