From 953ce379136b00fead094d128c14d427300587f9 Mon Sep 17 00:00:00 2001
From: Marc Wouts <marc.wouts@gmail.com>
Date: Sat, 2 Nov 2019 23:49:32 +0100
Subject: [PATCH] Multiple pairing in Jupytext's contents manager

#290
---
 HISTORY.rst                   |  1 +
 jupytext/contentsmanager.py   | 22 ++++++++++++--------
 tests/test_contentsmanager.py | 38 +++++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/HISTORY.rst b/HISTORY.rst
index 04c4a5eb1..1a671da22 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -8,6 +8,7 @@ Release History
 
 **Improvements**
 
+- Pairing a notebook to both `.md` and `.py` is now supported in Jupyter. Input cells are loaded from the most recent text representation. (#290).
 - Raw cells are now encoded using HTML comments (``<!-- #raw -->`` and ``<!-- #endraw -->``) in Markdown files (#321)
 - Markdown cells can be delimited with any of ``<!-- #region -->``,  ``<!-- #markdown -->`` or ``<!-- #md -->`` (#344)
 - Code blocks from Markdown files, when they don't have an explicit language, appear in Markdown cells in Jupyter (#321)
diff --git a/jupytext/contentsmanager.py b/jupytext/contentsmanager.py
index add9266ac..2aa0d0428 100644
--- a/jupytext/contentsmanager.py
+++ b/jupytext/contentsmanager.py
@@ -350,17 +350,23 @@ def get(self, path, content=True, type=None, format=None, load_alternative_forma
             path_inputs = path_outputs = path
             model_outputs = None
 
-            # Source format is first non ipynb format found on disk
+            # Source format is the most recent non ipynb format found on disk
             if path.endswith('.ipynb'):
+                most_recent_timestamp = None
                 for alt_path, alt_fmt in alt_paths:
                     if not alt_path.endswith('.ipynb') and self.exists(alt_path):
-                        self.log.info(u'Reading SOURCE from {}'.format(alt_path))
-                        path_inputs = alt_path
-                        fmt_inputs = alt_fmt
-                        model_outputs = model
-                        model = self.get(alt_path, content=content, type='notebook', format=format,
-                                         load_alternative_format=False)
-                        break
+                        alt_model = self._notebook_model(alt_path, content=False)
+                        if most_recent_timestamp is None or alt_model['last_modified'] > most_recent_timestamp:
+                            most_recent_timestamp = alt_model['last_modified']
+                            model_outputs = model
+                            path_inputs = alt_path
+                            fmt_inputs = alt_fmt
+
+                if most_recent_timestamp is not None:
+                    self.log.info(u'Reading SOURCE from {}'.format(path_inputs))
+                    model = self.get(path_inputs, content=content, type='notebook', format=format,
+                                     load_alternative_format=False)
+
             # Outputs taken from ipynb if in group, if file exists
             else:
                 for alt_path, _ in alt_paths:
diff --git a/tests/test_contentsmanager.py b/tests/test_contentsmanager.py
index 388904499..728f10102 100644
--- a/tests/test_contentsmanager.py
+++ b/tests/test_contentsmanager.py
@@ -1543,3 +1543,41 @@ class SubClassTextFileContentsManager(jupytext.TextFileContentsManager):
 
     assert not isinstance(SubClassTextFileContentsManager, jupytext.TextFileContentsManager)
     assert issubclass(SubClassTextFileContentsManager, jupytext.TextFileContentsManager)
+
+
+def test_multiple_pairing(tmpdir):
+    """Test that multiple pairing works. Input cells are loaded from the most recent text representation among
+    the paired ones"""
+    tmp_ipynb = str(tmpdir.join('notebook.ipynb'))
+    tmp_md = str(tmpdir.join('notebook.md'))
+    tmp_py = str(tmpdir.join('notebook.py'))
+
+    def nb(text):
+        return new_notebook(cells=[new_markdown_cell(text)],
+                            metadata={'jupytext': {'formats': 'ipynb,md,py'}})
+
+    cm = jupytext.TextFileContentsManager()
+    cm.root_dir = str(tmpdir)
+
+    cm.save(model=dict(type='notebook', content=nb('saved from cm')), path='notebook.ipynb')
+    compare_notebooks(jupytext.read(tmp_ipynb), nb('saved from cm'))
+    compare_notebooks(jupytext.read(tmp_md), nb('saved from cm'))
+    compare_notebooks(jupytext.read(tmp_py), nb('saved from cm'))
+
+    jupytext.write(nb('md edited'), tmp_md)
+    model = cm.get('notebook.ipynb')
+    compare_notebooks(model['content'], nb('md edited'))
+
+    cm.save(model=model, path='notebook.ipynb')
+    compare_notebooks(jupytext.read(tmp_ipynb), nb('md edited'))
+    compare_notebooks(jupytext.read(tmp_md), nb('md edited'))
+    compare_notebooks(jupytext.read(tmp_py), nb('md edited'))
+
+    jupytext.write(nb('py edited'), tmp_py)
+    model = cm.get('notebook.ipynb')
+    compare_notebooks(model['content'], nb('py edited'))
+
+    cm.save(model=model, path='notebook.ipynb')
+    compare_notebooks(jupytext.read(tmp_ipynb), nb('py edited'))
+    compare_notebooks(jupytext.read(tmp_md), nb('py edited'))
+    compare_notebooks(jupytext.read(tmp_py), nb('py edited'))