From 2b6c8b33be0e66160c6f5d14fd78c7a47e3389b0 Mon Sep 17 00:00:00 2001
From: Takeshi KOMIYA <i.tkomiya@gmail.com>
Date: Wed, 24 Jan 2018 21:33:33 +0900
Subject: [PATCH] Fix all files are treated as reST if old styled source_suffix
 used

---
 sphinx/config.py   | 11 +++++++----
 sphinx/registry.py | 11 ++++++++---
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/sphinx/config.py b/sphinx/config.py
index 88453b891..34cbf0883 100644
--- a/sphinx/config.py
+++ b/sphinx/config.py
@@ -371,11 +371,14 @@ def convert_source_suffix(app, config):
     """
     source_suffix = config.source_suffix
     if isinstance(source_suffix, string_types):
-        # if str, considers as reST
-        config.source_suffix = OrderedDict({source_suffix: 'restructuredtext'})  # type: ignore
+        # if str, considers as default filetype (None)
+        #
+        # The default filetype is determined on later step.
+        # By default, it is considered as restructuredtext.
+        config.source_suffix = OrderedDict({source_suffix: None})  # type: ignore
     elif isinstance(source_suffix, (list, tuple)):
-        # if list, considers as all of them are reST
-        config.source_suffix = OrderedDict([(s, 'restructuredtext') for s in source_suffix])  # type: ignore  # NOQA
+        # if list, considers as all of them are default filetype
+        config.source_suffix = OrderedDict([(s, None) for s in source_suffix])  # type: ignore  # NOQA
     elif isinstance(source_suffix, dict):
         # if dict, convert it to OrderedDict
         config.source_suffix = OrderedDict(config.source_suffix)  # type: ignore
diff --git a/sphinx/registry.py b/sphinx/registry.py
index ba01978cc..953fcf211 100644
--- a/sphinx/registry.py
+++ b/sphinx/registry.py
@@ -233,7 +233,8 @@ class SphinxComponentRegistry(object):
         # type: (unicode) -> unicode
         for suffix, filetype in iteritems(self.source_suffix):
             if filename.endswith(suffix):
-                return filetype
+                # If default filetype (None), considered as restructuredtext.
+                return filetype or 'restructuredtext'
         else:
             raise FiletypeNotFoundError
 
@@ -273,8 +274,8 @@ class SphinxComponentRegistry(object):
         try:
             filetype = self.get_filetype(filename)
             input_class = self.source_inputs[filetype]
-        except FiletypeNotFoundError:
-            # use special source_input for unknown file-type '*' (if exists)
+        except (FiletypeNotFoundError, KeyError):
+            # use special source_input for unknown filetype
             input_class = self.source_inputs.get('*')
 
         if input_class is None:
@@ -377,6 +378,10 @@ def merge_source_suffix(app):
     for suffix in app.registry.source_suffix:
         if suffix not in app.config.source_suffix:
             app.config.source_suffix[suffix] = suffix
+        elif app.config.source_suffix[suffix] is None:
+            # filetype is not specified (default filetype).
+            # So it overrides default filetype by extensions setting.
+            app.config.source_suffix[suffix] = suffix
 
     # copy config.source_suffix to registry
     app.registry.source_suffix = app.config.source_suffix