From 768b49750fd2a9ba4382f44960108b985d0ac405 Mon Sep 17 00:00:00 2001
From: "[6~" <inform@tiker.net>
Date: Thu, 17 Oct 2019 14:23:07 -0500
Subject: [PATCH] Deprecate Stringifier.constant_mapper

---
 pymbolic/mapper/stringifier.py | 20 ++++++++++++++------
 pymbolic/primitives.py         | 12 +++++++-----
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/pymbolic/mapper/stringifier.py b/pymbolic/mapper/stringifier.py
index da65138..f1afc0f 100644
--- a/pymbolic/mapper/stringifier.py
+++ b/pymbolic/mapper/stringifier.py
@@ -87,11 +87,16 @@ class StringifyMapper(pymbolic.mapper.Mapper):
     method to get a :class:`StringifyMapper` that potentially does.
     """
 
-    def __init__(self, constant_mapper=str):
-        """
-        :arg constant_mapper: A function of a single *expr* argument being used
-            to map constants into strings.
-        """
+    def __init__(self, constant_mapper=None):
+        if constant_mapper is not None:
+            from warnings import warn
+            warn("Overriding constant_mapper is deprecated. "
+                    "Instead, subclass the stringifier to "
+                    "achieve the desired effect. "
+                    "The 'constant_mapper' argument will "
+                    "disappear after June 2020.",
+                    DeprecationWarning)
+
         self.constant_mapper = constant_mapper
 
     # {{{ replaceable string composition interface
@@ -140,7 +145,10 @@ class StringifyMapper(pymbolic.mapper.Mapper):
                 expr, enclosing_prec, *args, **kwargs)
 
     def map_constant(self, expr, enclosing_prec, *args, **kwargs):
-        result = self.constant_mapper(expr)
+        if self.constant_mapper is None:
+            result = str(expr)
+        else:
+            result = self.constant_mapper(expr)
 
         if not (result.startswith("(") and result.endswith(")")) \
                 and ("-" in result or "+" in result) \
diff --git a/pymbolic/primitives.py b/pymbolic/primitives.py
index 88cf8f5..0ca0a6d 100644
--- a/pymbolic/primitives.py
+++ b/pymbolic/primitives.py
@@ -452,9 +452,8 @@ class Expression(object):
         a subclass of :class:`pymbolic.mapper.stringifier.StringifyMapper`.
 
         :arg originating_stringifier: If provided, the newly created
-            stringifier should use attributes and settings of
-            *originating_stringifier*, e.g. the
-            :attr:`pymbolic.mapper.StringifyMapper.constant_mapper`.
+            stringifier should carry forward attributes and settings of
+            *originating_stringifier*.
         """
         if originating_stringifier is None:
             stringify_mapper_args = ()
@@ -469,8 +468,11 @@ class Expression(object):
         else:
             from warnings import warn
             warn("%s overrides 'stringifier', which is deprecated. "
-                    "Override 'make_stringifier' instead."
-                    % type(self).__name__)
+                    "Override 'make_stringifier' instead. "
+                    "Backward compatibility will go away "
+                    "sometime after June 2020."
+                    % type(self).__name__,
+                    DeprecationWarning)
 
             return stringifier_class_getter()(*stringify_mapper_args)
 
-- 
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