Use default repr() for quoted_name under python 3

Changed the ``repr()`` of the :class:`.quoted_name` construct to use
regular string repr() under Python 3, rather than running it through
"backslashreplace" escaping, which can be misleading.

Modified the approach of "name normalization" for the Oracle and Firebird
dialects, which converts from the UPPERCASE-as-case-insensitive convention
of these dialects into lowercase-as-case-insensitive for SQLAlchemy, to not
automatically apply the :class:`.quoted_name` construct to a name that
matches itself under upper or lower case conversion, as is the case for
many non-european characters.   All names used within metadata structures
are converted to :class:`.quoted_name` objects in any case; the change
here would only affect the output of some inspection functions.

Moved name normalize to be under default dialect, added test coverage
in test/sql/test_quote.py

Fixes: #4931
Change-Id: Ic121b20e07249824710a54423e321d94a425362f

1 files changed, 52 insertions, 0 deletions

diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 79b8622d5..d1253f678 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -29,6 +29,7 @@ from .. import util
 from ..sql import compiler
 from ..sql import expression
 from ..sql import schema
+from ..sql.elements import quoted_name
 
 
 AUTOCOMMIT_REGEXP = re.compile(
@@ -580,6 +581,57 @@ class DefaultDialect(interfaces.Dialect):
         # the configured default of this dialect.
         self.set_isolation_level(dbapi_conn, self.default_isolation_level)
 
+    def normalize_name(self, name):
+        if name is None:
+            return None
+        if util.py2k:
+            if isinstance(name, str):
+                name = name.decode(self.encoding)
+
+        name_lower = name.lower()
+        name_upper = name.upper()
+
+        if name_upper == name_lower:
+            # name has no upper/lower conversion, e.g. non-european characters.
+            # return unchanged
+            return name
+        elif name_upper == name and not (
+            self.identifier_preparer._requires_quotes
+        )(name_lower):
+            # name is all uppercase and doesn't require quoting; normalize
+            # to all lower case
+            return name_lower
+        elif name_lower == name:
+            # name is all lower case, which if denormalized means we need to
+            # force quoting on it
+            return quoted_name(name, quote=True)
+        else:
+            # name is mixed case, means it will be quoted in SQL when used
+            # later, no normalizes
+            return name
+
+    def denormalize_name(self, name):
+        if name is None:
+            return None
+
+        name_lower = name.lower()
+        name_upper = name.upper()
+
+        if name_upper == name_lower:
+            # name has no upper/lower conversion, e.g. non-european characters.
+            # return unchanged
+            return name
+        elif name_lower == name and not (
+            self.identifier_preparer._requires_quotes
+        )(name_lower):
+            name = name_upper
+        if util.py2k:
+            if not self.supports_unicode_binds:
+                name = name.encode(self.encoding)
+            else:
+                name = unicode(name)  # noqa
+        return name
+
 
 class StrCompileDialect(DefaultDialect):