From 4b97692d9d1b1feba76b55b90df51385b9bbbbf2 Mon Sep 17 00:00:00 2001
From: Keewis <keewis@posteo.de>
Date: Thu, 20 Aug 2020 19:32:31 +0200
Subject: [PATCH 1/3] override the signature of plotfunc

---
 xarray/plot/plot.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/xarray/plot/plot.py b/xarray/plot/plot.py
index 305405d4e5a..bc6c9ec52f9 100644
--- a/xarray/plot/plot.py
+++ b/xarray/plot/plot.py
@@ -463,6 +463,15 @@ def step(self, *args, **kwargs):
         return step(self._da, *args, **kwargs)
 
 
+def override_signature(f):
+    def wrapper(func):
+        func.__wrapped__ = f
+
+        return func
+
+    return wrapper
+
+
 def _plot2d(plotfunc):
     """
     Decorator for common 2d plotting logic
@@ -572,6 +581,10 @@ def _plot2d(plotfunc):
     # Build on the original docstring
     plotfunc.__doc__ = f"{plotfunc.__doc__}\n{commondoc}"
 
+    def signature(darray, x, y, **kwargs):
+        pass
+
+    @override_signature(signature)
     @functools.wraps(plotfunc)
     def newplotfunc(
         darray,

From 9b7479cacfc9e9fcc75fa52a0954855d5d4e5633 Mon Sep 17 00:00:00 2001
From: Keewis <keewis@posteo.de>
Date: Thu, 20 Aug 2020 19:40:06 +0200
Subject: [PATCH 2/3] update whats-new.rst

---
 doc/whats-new.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index 823c3e2e1b2..60201418873 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -73,6 +73,7 @@ Bug fixes
   and :py:meth:`DataArray.str.wrap` (:issue:`4334`). By `Mathias Hauser <https://github.com/mathause>`_.
 - Fixed overflow issue causing incorrect results in computing means of :py:class:`cftime.datetime`
   arrays (:issue:`4341`). By `Spencer Clark <https://github.com/spencerkclark>`_.
+- fix the signature of the plot methods. (:pull:`4359`) By `Justus Magin <https://github.com/keewis>`_.
 
 Documentation
 ~~~~~~~~~~~~~

From 1154d199d0ba5b42e02921e8eb8eee557d0dc8f6 Mon Sep 17 00:00:00 2001
From: Keewis <keewis@posteo.de>
Date: Tue, 25 Aug 2020 15:12:35 +0200
Subject: [PATCH 3/3] explain the reasons for the signature dummy

---
 xarray/plot/plot.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xarray/plot/plot.py b/xarray/plot/plot.py
index bc6c9ec52f9..0d44d5fd64a 100644
--- a/xarray/plot/plot.py
+++ b/xarray/plot/plot.py
@@ -581,6 +581,12 @@ def _plot2d(plotfunc):
     # Build on the original docstring
     plotfunc.__doc__ = f"{plotfunc.__doc__}\n{commondoc}"
 
+    # plotfunc and newplotfunc have different signatures:
+    # - plotfunc: (x, y, z, ax, **kwargs)
+    # - newplotfunc: (darray, x, y, **kwargs)
+    # where plotfunc accepts numpy arrays, while newplotfunc accepts a DataArray
+    # and variable names. newplotfunc also explicitly lists most kwargs, so we
+    # need to shorten it
     def signature(darray, x, y, **kwargs):
         pass