keep dictionaries ordered for doctesting

src/sage/doctest/forker.py

@@ -51,6 +51,7 @@
 from dis import findlinestarts
 from queue import Empty
 import gc
+import IPython.lib.pretty
 
 import sage.misc.randstate as randstate
 from .util import Timer, RecordingDict, count_noun
@@ -86,6 +87,32 @@
        exc is not OSError
 ]
 
+def _sorted_dict_pprinter_factory(start, end):
+    """
+    Modified version of :func:`IPython.lib.pretty._dict_pprinter_factory`
+    that sorts the keys of dictionaries for printing.
+
+    EXAMPLES::
+
+        sage: {2: 0, 1: 0} # indirect doctest
+        {1: 0, 2: 0}
+    """
+    def inner(obj, p, cycle):
+        if cycle:
+            return p.text('{...}')
+        step = len(start)
+        p.begin_group(step, start)
+        keys = obj.keys()
+        keys = IPython.lib.pretty._sorted_for_pprint(keys)
+        for idx, key in p._enumerate(keys):
+            if idx:
+                p.text(',')
+                p.breakable()
+            p.pretty(key)
+            p.text(': ')
+            p.pretty(obj[key])
+        p.end_group(step, end)
+    return inner
 
 
 def init_sage():
@@ -185,11 +212,11 @@ def init_sage():
     # IPython's pretty printer sorts the repr of dicts by their keys by default
     # (or their keys' str() if they are not otherwise orderable).  However, it
     # disables this for CPython 3.6+ opting to instead display dicts' "natural"
-    # insertion order, which is preserved in those versions).  This makes for
-    # inconsistent results with Python 2 tests that return dicts, so here we
-    # force the Python 2 style dict printing
-    import IPython.lib.pretty
-    IPython.lib.pretty.DICT_IS_ORDERED = False
+    # insertion order, which is preserved in those versions).
+    # However, this order is random in some instances.
+    # Also modifications of code may affect the order.
+    # So here we fore sorted dict printing.
+    IPython.lib.pretty.for_type(dict, _sorted_dict_pprinter_factory('{', '}'))
 
     # Switch on extra debugging
     from sage.structure.debug_options import debug