Render N'' for SQL Server unicode literals

The ``literal_processor`` for the :class:`.Unicode` and
:class:`.UnicodeText` datatypes now render an ``N`` character in front of
the literal string expression as required by SQL Server for Unicode string
values rendered in SQL expressions.

Note that this adds full unicode characters to the standard test suite,
which means we also need to bump MySQL provisioning up to utf8mb4.
Modern installs do not seem to be reproducing the 1271 issue locally,
if it reproduces in CI it would be better for us to skip those ORM-centric
tests for MySQL.

Also remove unused _StringType from SQL Server dialect

Fixes: #4442
Change-Id: Id55817b3e8a2d81ddc8b7b27f85e3f1dcc1cea7e

doc/build/changelog/unreleased_13/4442.rst

@@ -0,0 +1,8 @@
+.. change::
+   :tags: bug, mssql
+   :tickets: 4222
+
+   The ``literal_processor`` for the :class:`.Unicode` and
+   :class:`.UnicodeText` datatypes now render an ``N`` character in front of
+   the literal string expression as required by SQL Server for Unicode string
+   values rendered in SQL expressions.

lib/sqlalchemy/dialects/mssql/base.py

@@ -1003,12 +1003,26 @@ def __init__(self, precision=None, **kwargs):
         self.precision = precision
 
 
-class _StringType(object):
+class _UnicodeLiteral(object):
+    def literal_processor(self, dialect):
+        def process(value):
+
+            value = value.replace("'", "''")
+
+            if dialect.identifier_preparer._double_percents:
+                value = value.replace("%", "%%")
+
+            return "N'%s'" % value
+
+        return process
+
 
-    """Base for MSSQL string types."""
+class _MSUnicode(_UnicodeLiteral, sqltypes.Unicode):
+    pass
 
-    def __init__(self, collation=None):
-        super(_StringType, self).__init__(collation=collation)
+
+class _MSUnicodeText(_UnicodeLiteral, sqltypes.UnicodeText):
+    pass
 
 
 class TIMESTAMP(sqltypes._Binary):
@@ -2124,6 +2138,8 @@ class MSDialect(default.DefaultDialect):
         sqltypes.DateTime: _MSDateTime,
         sqltypes.Date: _MSDate,
         sqltypes.Time: TIME,
+        sqltypes.Unicode: _MSUnicode,
+        sqltypes.UnicodeText: _MSUnicodeText,
     }
 
     engine_config_types = default.DefaultDialect.engine_config_types.union(

lib/sqlalchemy/testing/provision.py

@@ -207,15 +207,12 @@ def _mysql_create_db(cfg, eng, ident):
         except Exception:
             pass
 
-        # using utf8mb4 we are getting collation errors on UNIONS:
-        # test/orm/inheritance/test_polymorphic_rel.py"
-        # 1271, u"Illegal mix of collations for operation 'UNION'"
-        conn.execute("CREATE DATABASE %s CHARACTER SET utf8mb3" % ident)
+        conn.execute("CREATE DATABASE %s CHARACTER SET utf8mb4" % ident)
         conn.execute(
-            "CREATE DATABASE %s_test_schema CHARACTER SET utf8mb3" % ident
+            "CREATE DATABASE %s_test_schema CHARACTER SET utf8mb4" % ident
         )
         conn.execute(
-            "CREATE DATABASE %s_test_schema_2 CHARACTER SET utf8mb3" % ident
+            "CREATE DATABASE %s_test_schema_2 CHARACTER SET utf8mb4" % ident
         )
 
 

lib/sqlalchemy/testing/requirements.py

@@ -732,6 +732,13 @@ def empty_strings_text(self):
 
         return exclusions.open()
 
+    @property
+    def expressions_against_unbounded_text(self):
+        """target database supports use of an unbounded textual field in a
+        WHERE clause."""
+
+        return exclusions.open()
+
     @property
     def selectone(self):
         """target driver must support the literal statement 'select 1'"""

lib/sqlalchemy/testing/suite/test_types.py

@@ -38,6 +38,8 @@
 
 
 class _LiteralRoundTripFixture(object):
+    supports_whereclause = True
+
     @testing.provide_metadata
     def _literal_round_trip(self, type_, input_, output, filter_=None):
         """test literal rendering """
@@ -49,33 +51,47 @@ def _literal_round_trip(self, type_, input_, output, filter_=None):
         t = Table("t", self.metadata, Column("x", type_))
         t.create()
 
-        for value in input_:
-            ins = (
-                t.insert()
-                .values(x=literal(value))
-                .compile(
-                    dialect=testing.db.dialect,
-                    compile_kwargs=dict(literal_binds=True),
+        with testing.db.connect() as conn:
+            for value in input_:
+                ins = (
+                    t.insert()
+                    .values(x=literal(value))
+                    .compile(
+                        dialect=testing.db.dialect,
+                        compile_kwargs=dict(literal_binds=True),
+                    )
                 )
-            )
-            testing.db.execute(ins)
+                conn.execute(ins)
+
+            if self.supports_whereclause:
+                stmt = t.select().where(t.c.x == literal(value))
+            else:
+                stmt = t.select()
 
-        for row in t.select().execute():
-            value = row[0]
-            if filter_ is not None:
-                value = filter_(value)
-            assert value in output
+            stmt = stmt.compile(
+                dialect=testing.db.dialect,
+                compile_kwargs=dict(literal_binds=True),
+            )
+            for row in conn.execute(stmt):
+                value = row[0]
+                if filter_ is not None:
+                    value = filter_(value)
+                assert value in output
 
 
 class _UnicodeFixture(_LiteralRoundTripFixture):
     __requires__ = ("unicode_data",)
 
     data = u(
-        "Alors vous imaginez ma surprise, au lever du jour, "
-        "quand une drôle de petite voix m’a réveillé. Elle "
-        "disait: « S’il vous plaît… dessine-moi un mouton! »"
+        "Alors vous imaginez ma 🐍 surprise, au lever du jour, "
+        "quand une drôle de petite 🐍 voix m’a réveillé. Elle "
+        "disait: « S’il vous plaît… dessine-moi 🐍 un mouton! »"
     )
 
+    @property
+    def supports_whereclause(self):
+        return config.requirements.expressions_against_unbounded_text.enabled
+
     @classmethod
     def define_tables(cls, metadata):
         Table(
@@ -122,6 +138,11 @@ def _test_empty_strings(self):
     def test_literal(self):
         self._literal_round_trip(self.datatype, [self.data], [self.data])
 
+    def test_literal_non_ascii(self):
+        self._literal_round_trip(
+            self.datatype, [util.u("réve🐍 illé")], [util.u("réve🐍 illé")]
+        )
+
 
 class UnicodeVarcharTest(_UnicodeFixture, fixtures.TablesTest):
     __requires__ = ("unicode_data",)
@@ -149,6 +170,10 @@ class TextTest(_LiteralRoundTripFixture, fixtures.TablesTest):
     __requires__ = ("text_type",)
     __backend__ = True
 
+    @property
+    def supports_whereclause(self):
+        return config.requirements.expressions_against_unbounded_text.enabled
+
     @classmethod
     def define_tables(cls, metadata):
         Table(
@@ -177,6 +202,11 @@ def test_text_empty_strings(self):
     def test_literal(self):
         self._literal_round_trip(Text, ["some text"], ["some text"])
 
+    def test_literal_non_ascii(self):
+        self._literal_round_trip(
+            Text, [util.u("réve🐍 illé")], [util.u("réve🐍 illé")]
+        )
+
     def test_literal_quoting(self):
         data = """some 'text' hey "hi there" that's text"""
         self._literal_round_trip(Text, [data], [data])
@@ -202,8 +232,15 @@ def test_nolength_string(self):
         foo.drop(config.db)
 
     def test_literal(self):
+        # note that in Python 3, this invokes the Unicode
+        # datatype for the literal part because all strings are unicode
         self._literal_round_trip(String(40), ["some text"], ["some text"])
 
+    def test_literal_non_ascii(self):
+        self._literal_round_trip(
+            String(40), [util.u("réve🐍 illé")], [util.u("réve🐍 illé")]
+        )
+
     def test_literal_quoting(self):
         data = """some 'text' hey "hi there" that's text"""
         self._literal_round_trip(String(40), [data], [data])
@@ -864,17 +901,17 @@ def test_unicode_round_trip(self):
                 {
                     "name": "r1",
                     "data": {
-                        util.u("réveillé"): util.u("réveillé"),
-                        "data": {"k1": util.u("drôle")},
+                        util.u("réve🐍 illé"): util.u("réve🐍 illé"),
+                        "data": {"k1": util.u("drôl🐍e")},
                     },
                 },
             )
 
             eq_(
                 conn.scalar(select([self.tables.data_table.c.data])),
                 {
-                    util.u("réveillé"): util.u("réveillé"),
-                    "data": {"k1": util.u("drôle")},
+                    util.u("réve🐍 illé"): util.u("réve🐍 illé"),
+                    "data": {"k1": util.u("drôl🐍e")},
                 },
             )
 

setup.cfg

@@ -66,8 +66,8 @@ postgresql=postgresql://scott:tiger@127.0.0.1:5432/test
 pg8000=postgresql+pg8000://scott:tiger@127.0.0.1:5432/test
 postgresql_psycopg2cffi=postgresql+psycopg2cffi://scott:tiger@127.0.0.1:5432/test
 
-mysql=mysql://scott:tiger@127.0.0.1:3306/test?charset=utf8
-pymysql=mysql+pymysql://scott:tiger@127.0.0.1:3306/test?charset=utf8
+mysql=mysql://scott:tiger@127.0.0.1:3306/test?charset=utf8mb4
+pymysql=mysql+pymysql://scott:tiger@127.0.0.1:3306/test?charset=utf8mb4
 
 mssql=mssql+pyodbc://scott:tiger@ms_2008
 mssql_pymssql=mssql+pymssql://scott:tiger@ms_2008

test/dialect/mssql/test_types.py

@@ -7,13 +7,15 @@
 import sqlalchemy as sa
 from sqlalchemy import Boolean
 from sqlalchemy import Column
+from sqlalchemy import column
 from sqlalchemy import Date
 from sqlalchemy import DateTime
 from sqlalchemy import DefaultClause
 from sqlalchemy import Float
 from sqlalchemy import inspect
 from sqlalchemy import Integer
 from sqlalchemy import LargeBinary
+from sqlalchemy import literal
 from sqlalchemy import MetaData
 from sqlalchemy import Numeric
 from sqlalchemy import PickleType
@@ -27,7 +29,9 @@
 from sqlalchemy import text
 from sqlalchemy import Time
 from sqlalchemy import types
+from sqlalchemy import Unicode
 from sqlalchemy import UnicodeText
+from sqlalchemy import util
 from sqlalchemy.databases import mssql
 from sqlalchemy.dialects.mssql import ROWVERSION
 from sqlalchemy.dialects.mssql import TIMESTAMP
@@ -37,6 +41,7 @@
 from sqlalchemy.dialects.mssql.base import TIME
 from sqlalchemy.sql import sqltypes
 from sqlalchemy.testing import assert_raises_message
+from sqlalchemy.testing import AssertsCompiledSQL
 from sqlalchemy.testing import AssertsExecutionResults
 from sqlalchemy.testing import ComparesTables
 from sqlalchemy.testing import emits_warning_on
@@ -922,6 +927,49 @@ def test_autoincrement(self):
                 engine.execute(tbl.delete())
 
 
+class StringTest(fixtures.TestBase, AssertsCompiledSQL):
+    __dialect__ = mssql.dialect()
+
+    def test_unicode_literal_binds(self):
+        self.assert_compile(
+            column("x", Unicode()) == "foo", "x = N'foo'", literal_binds=True
+        )
+
+    def test_unicode_text_literal_binds(self):
+        self.assert_compile(
+            column("x", UnicodeText()) == "foo",
+            "x = N'foo'",
+            literal_binds=True,
+        )
+
+    def test_string_text_literal_binds(self):
+        self.assert_compile(
+            column("x", String()) == "foo", "x = 'foo'", literal_binds=True
+        )
+
+    def test_string_text_literal_binds_explicit_unicode_right(self):
+        self.assert_compile(
+            column("x", String()) == util.u("foo"),
+            "x = 'foo'",
+            literal_binds=True,
+        )
+
+    def test_string_text_explicit_literal_binds(self):
+        # the literal experssion here coerces the right side to
+        # Unicode on Python 3 for plain string, test with unicode
+        # string just to confirm literal is doing this
+        self.assert_compile(
+            column("x", String()) == literal(util.u("foo")),
+            "x = N'foo'",
+            literal_binds=True,
+        )
+
+    def test_text_text_literal_binds(self):
+        self.assert_compile(
+            column("x", Text()) == "foo", "x = 'foo'", literal_binds=True
+        )
+
+
 class BinaryTest(fixtures.TestBase):
     __only_on__ = "mssql"
     __requires__ = ("non_broken_binary",)

test/requirements.py

@@ -662,6 +662,16 @@ def empty_strings_text(self):
 
         return exclusions.open()
 
+    @property
+    def expressions_against_unbounded_text(self):
+        """target database supports use of an unbounded textual field in a
+        WHERE clause."""
+
+        return fails_if(
+            ["oracle"],
+            "ORA-00932: inconsistent datatypes: expected - got CLOB",
+        )
+
     @property
     def unicode_data(self):
         """target drive must support unicode data stored in columns."""
@@ -1173,9 +1183,9 @@ def get_order_by_collation(self, config):
         lookup = {
             # will raise without quoting
             "postgresql": "POSIX",
-            # note MySQL databases need to be created w/ utf8mb3 charset
+            # note MySQL databases need to be created w/ utf8mb4 charset
             # for the test suite
-            "mysql": "utf8mb3_bin",
+            "mysql": "utf8mb4_bin",
             "sqlite": "NOCASE",
             # will raise *with* quoting
             "mssql": "Latin1_General_CI_AS",