From 0ac710d2026b8dca3452b8c50d1417fefd3f62b7 Mon Sep 17 00:00:00 2001
From: Matthias Bussonnier <bussonniermatthias@gmail.com>
Date: Thu, 18 Jul 2019 21:10:04 -0700
Subject: [PATCH] [Experiement] Auto-expand signature when **kwarg passed to
 other functions.

Many functions current takes **kwargs and pass them down. During a SciPy
discussion it was brought up that this was sub-optimal for new user.

We can use the fact that signature can be faked, and inspect to
propagate the actual keyword arguments and substitute them for **kwargs
in another.

With this, the signature of pyplot.subplots(), which currently as viewed
in IPython is

    plt.subplots(
        nrows=1,
        ncols=1,
        sharex=False,
        sharey=False,
        squeeze=True,
        subplot_kw=None,
        gridspec_kw=None,
        **fig_kw,
    )

now becomes:

    plt.subplots(
        nrows=1,
        ncols=1,
        sharex=False,
        sharey=False,
        squeeze=True,
        subplot_kw=None,
        gridspec_kw=None,
    +   num=None,
    +   figsize=None,
    +   dpi=None,
    +   facecolor=None,
    +   edgecolor=None,
    +   frameon=True,
    +   FigureClass=<class 'matplotlib.figure.Figure'>,
    +   clear=False,
    +   **kwargs, # used to be **fig_kw, to fix.
    )

... which is not totally correct (they are kwargs only...) but you
should see the point.

This is nice as:

1) it now appear in IPython ? and ??
2) tab completion pick up these kwargs.

And it should have minimal overhead at import time, and is so far
limited to function that pass all of **kwarg.

Many places in matplotlib are also too dynamic to properly do it, but
could allow a manual variant.
---
 lib/matplotlib/pyplot.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
index 65ea7a9db423..88ff59edf3a9 100644
--- a/lib/matplotlib/pyplot.py
+++ b/lib/matplotlib/pyplot.py
@@ -1038,7 +1038,25 @@ def subplot(*args, **kwargs):
 
     return a
 
+def inherit(target):
 
+    def decorate(function):
+        sig =  inspect.signature(target)
+        parameters = sig.parameters
+        
+        current_sig = inspect.signature(function)
+        current_params = [(k,v) for k,v in current_sig.parameters.items()]
+        if current_params[-1][1].kind == inspect.Parameter.VAR_KEYWORD:
+            del current_params[-1]
+            current_params.extend([(k,v) for k,v in parameters.items()])
+        new_sig = inspect.Signature([v for k,v in current_params])
+        function.__signature__ = new_sig
+        return function
+
+    return decorate
+
+
+@inherit(figure)
 def subplots(nrows=1, ncols=1, sharex=False, sharey=False, squeeze=True,
              subplot_kw=None, gridspec_kw=None, **fig_kw):
     """