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

4 files changed, 59 insertions, 60 deletions

diff --git a/lib/sqlalchemy/dialects/firebird/base.py b/lib/sqlalchemy/dialects/firebird/base.py
index a852c7824..c7c921cb4 100644
--- a/lib/sqlalchemy/dialects/firebird/base.py
+++ b/lib/sqlalchemy/dialects/firebird/base.py
@@ -86,7 +86,6 @@ from sqlalchemy.engine import default
 from sqlalchemy.engine import reflection
 from sqlalchemy.sql import compiler
 from sqlalchemy.sql import expression
-from sqlalchemy.sql.elements import quoted_name
 from sqlalchemy.types import BIGINT
 from sqlalchemy.types import BLOB
 from sqlalchemy.types import DATE
@@ -659,31 +658,6 @@ class FBDialect(default.DefaultDialect):
             "implicit_returning", True
         )
 
-    def normalize_name(self, name):
-        # Remove trailing spaces: FB uses a CHAR() type,
-        # that is padded with spaces
-        name = name and name.rstrip()
-        if name is None:
-            return None
-        elif name.upper() == name and not (
-            self.identifier_preparer._requires_quotes
-        )(name.lower()):
-            return name.lower()
-        elif name.lower() == name:
-            return quoted_name(name, quote=True)
-        else:
-            return name
-
-    def denormalize_name(self, name):
-        if name is None:
-            return None
-        elif name.lower() == name and not (
-            self.identifier_preparer._requires_quotes
-        )(name.lower()):
-            return name.upper()
-        else:
-            return name
-
     def has_table(self, connection, table_name, schema=None):
         """Return ``True`` if the given table exists, ignoring
         the `schema`."""
diff --git a/lib/sqlalchemy/dialects/oracle/base.py b/lib/sqlalchemy/dialects/oracle/base.py
index 48b90f7e9..4c5a717b9 100644
--- a/lib/sqlalchemy/dialects/oracle/base.py
+++ b/lib/sqlalchemy/dialects/oracle/base.py
@@ -457,7 +457,6 @@ from ...sql import compiler
 from ...sql import expression
 from ...sql import util as sql_util
 from ...sql import visitors
-from ...sql.elements import quoted_name
 from ...types import BLOB
 from ...types import CHAR
 from ...types import CLOB
@@ -1388,35 +1387,6 @@ class OracleDialect(default.DefaultDialect):
         )
         return cursor.first() is not None
 
-    def normalize_name(self, name):
-        if name is None:
-            return None
-        if util.py2k:
-            if isinstance(name, str):
-                name = name.decode(self.encoding)
-        if name.upper() == name and not (
-            self.identifier_preparer._requires_quotes
-        )(name.lower()):
-            return name.lower()
-        elif name.lower() == name:
-            return quoted_name(name, quote=True)
-        else:
-            return name
-
-    def denormalize_name(self, name):
-        if name is None:
-            return None
-        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
-
     def _get_default_schema_name(self, connection):
         return self.normalize_name(
             connection.execute("SELECT USER FROM DUAL").scalar()
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):
 
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index 78c434cff..e1ff44285 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -4479,10 +4479,13 @@ class quoted_name(util.MemoizedSlots, util.text_type):
             return util.text_type(self).upper()
 
     def __repr__(self):
-        backslashed = self.encode("ascii", "backslashreplace")
-        if not util.py2k:
-            backslashed = backslashed.decode("ascii")
-        return "'%s'" % backslashed
+        if util.py2k:
+            backslashed = self.encode("ascii", "backslashreplace")
+            if not util.py2k:
+                backslashed = backslashed.decode("ascii")
+            return "'%s'" % backslashed
+        else:
+            return str.__repr__(self)
 
 
 def _select_iterables(elements):