#16333: use (",", ": ") as default separator when indent is specified to avoid trailing whitespace. Patch by Serhiy Storchaka.

2 files changed, 14 insertions, 9 deletions

diff --git a/Lib/json/__init__.py b/Lib/json/__init__.py
index 86a7a3e..7314cb4 100644
--- a/Lib/json/__init__.py
+++ b/Lib/json/__init__.py
@@ -148,9 +148,10 @@ def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
     level of 0 will only insert newlines. ``None`` is the most compact
     representation.
 
-    If ``separators`` is an ``(item_separator, dict_separator)`` tuple
-    then it will be used instead of the default ``(', ', ': ')`` separators.
-    ``(',', ':')`` is the most compact JSON representation.
+    If specified, ``separators`` should be an ``(item_separator, key_separator)``
+    tuple.  The default is ``(', ', ': ')`` if *indent* is ``None`` and
+    ``(',', ': ')`` otherwise.  To get the most compact JSON representation,
+    you should specify ``(',', ':')`` to eliminate whitespace.
 
     ``default(obj)`` is a function that should return a serializable version
     of obj or raise TypeError. The default simply raises TypeError.
@@ -209,9 +210,10 @@ def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
     level of 0 will only insert newlines. ``None`` is the most compact
     representation.
 
-    If ``separators`` is an ``(item_separator, dict_separator)`` tuple
-    then it will be used instead of the default ``(', ', ': ')`` separators.
-    ``(',', ':')`` is the most compact JSON representation.
+    If specified, ``separators`` should be an ``(item_separator, key_separator)``
+    tuple.  The default is ``(', ', ': ')`` if *indent* is ``None`` and
+    ``(',', ': ')`` otherwise.  To get the most compact JSON representation,
+    you should specify ``(',', ':')`` to eliminate whitespace.
 
     ``default(obj)`` is a function that should return a serializable version
     of obj or raise TypeError. The default simply raises TypeError.
diff --git a/Lib/json/encoder.py b/Lib/json/encoder.py
index ba57c2c..93b5ea7 100644
--- a/Lib/json/encoder.py
+++ b/Lib/json/encoder.py
@@ -127,9 +127,10 @@ class JSONEncoder(object):
         indent level.  An indent level of 0 will only insert newlines.
         None is the most compact representation.
 
-        If specified, separators should be a (item_separator, key_separator)
-        tuple.  The default is (', ', ': ').  To get the most compact JSON
-        representation you should specify (',', ':') to eliminate whitespace.
+        If specified, separators should be an (item_separator, key_separator)
+        tuple.  The default is (', ', ': ') if *indent* is ``None`` and
+        (',', ': ') otherwise.  To get the most compact JSON representation,
+        you should specify (',', ':') to eliminate whitespace.
 
         If specified, default is a function that gets called for objects
         that can't otherwise be serialized.  It should return a JSON encodable
@@ -145,6 +146,8 @@ class JSONEncoder(object):
         self.indent = indent
         if separators is not None:
             self.item_separator, self.key_separator = separators
+        elif indent is not None:
+            self.item_separator = ','
         if default is not None:
             self.default = default