Add _alembic_quote method to format_constraint()

Alembic needs a portable way of getting at the name of an
index without quoting being applied.   As we would like the
indexes created by the Column index=True flag to support
deferred index names, supply a function that delivers this
for Alembic without it having to dig too deeply into the
internals.    the _alembic_quote flag may be made public
at a later time, however as we've been through many quoting
flags that are difficult to get rid of, try to be conservative
to start.

Change-Id: I184adaeae26c2e75093aaea5ebe01a3815cadb08

1 files changed, 28 insertions, 0 deletions

diff --git a/test/sql/test_quote.py b/test/sql/test_quote.py
index b54da97ba..d7219b12d 100644
--- a/test/sql/test_quote.py
+++ b/test/sql/test_quote.py
@@ -868,6 +868,34 @@ class PreparerTest(fixtures.TestBase):
         a_eq(unformat("`foo`.bar"), ["foo", "bar"])
         a_eq(unformat("`foo`.`b``a``r`.`baz`"), ["foo", "b`a`r", "baz"])
 
+    def test_alembic_quote(self):
+        t1 = Table(
+            "TableOne", MetaData(), Column("MyCol", Integer, index=True)
+        )
+        t2 = Table(
+            "some_table", MetaData(), Column("some_col", Integer, index=True)
+        )
+        t3 = Table(
+            "some_table", MetaData(), Column("some_col", Integer, index=True)
+        )
+        ix3 = Index("my_index", t3.c.some_col)
+        ix4 = Index("MyIndex", t3.c.some_col)
+        ix5 = Index(None, t3.c.some_col)
+
+        for idx, expected in [
+            (list(t1.indexes)[0], "ix_TableOne_MyCol"),
+            (list(t2.indexes)[0], "ix_some_table_some_col"),
+            (ix3, "my_index"),
+            (ix4, "MyIndex"),
+            (ix5, "ix_some_table_some_col"),
+        ]:
+            eq_(
+                testing.db.dialect.identifier_preparer.format_constraint(
+                    idx, _alembic_quote=False
+                ),
+                expected,
+            )
+
 
 class QuotedIdentTest(fixtures.TestBase):
     def test_concat_quotetrue(self):