Ensure all Query statements compile w/ orm, fix test harness

Fixed regression where :meth:`_orm.Query.join` would produce no effect if
the query itself as well as the join target were against a
:class:`_schema.Table` object, rather than a mapped class. This was part of
a more systemic issue where the legacy ORM query compiler would not be
correctly used from a :class:`_orm.Query` if the statement produced had not
ORM entities present within it.

Also repair the assert_compile() method, which was using
Query._compile_state() which was bypassing the bug.   A handful
of ORM tests with Query objects and Core-only objects were actually
failing if the default compilation path were used.

Fixes: #6003
Change-Id: I97478b2d06bf6c01fe1f09ee118e1f2ac4c849bc

2 files changed, 13 insertions, 5 deletions

diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index c444b557b..d685ac83e 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -440,6 +440,15 @@ class Query(
             )
             stmt.__dict__.pop("session", None)
 
+        # ensure the ORM context is used to compile the statement, even
+        # if it has no ORM entities.  This is so ORM-only things like
+        # _legacy_joins are picked up that wouldn't be picked up by the
+        # Core statement context
+        if "compile_state_plugin" not in stmt._propagate_attrs:
+            stmt._propagate_attrs = stmt._propagate_attrs.union(
+                {"compile_state_plugin": "orm", "plugin_subject": None}
+            )
+
         return stmt
 
     def subquery(
@@ -2304,6 +2313,7 @@ class Query(
                 "is deprecated and will be removed in SQLAlchemy 2.0. "
                 "Please use individual join() calls per relationship."
             )
+
         self._legacy_setup_joins += joins_to_add
 
         self.__dict__.pop("_last_joined_entity", None)
diff --git a/lib/sqlalchemy/testing/assertions.py b/lib/sqlalchemy/testing/assertions.py
index 81c74e7c1..289ac9a0a 100644
--- a/lib/sqlalchemy/testing/assertions.py
+++ b/lib/sqlalchemy/testing/assertions.py
@@ -445,11 +445,9 @@ class AssertsCompiledSQL(object):
         from sqlalchemy import orm
 
         if isinstance(clause, orm.Query):
-            compile_state = clause._compile_state()
-            compile_state.statement._label_style = (
-                LABEL_STYLE_TABLENAME_PLUS_COL
-            )
-            clause = compile_state.statement
+            stmt = clause._statement_20()
+            stmt._label_style = LABEL_STYLE_TABLENAME_PLUS_COL
+            clause = stmt
 
         if compile_kwargs:
             kw["compile_kwargs"] = compile_kwargs