Ignore reflected expression based indexes

this establishes forwads-compatibility for
PostgreSQL expression-based index reflection
being added in I3e36d557235286c0f7f6d8276272ff9225058d48

Change-Id: I81d7832f254f50dc3417dd3437c2b49ec3a549e2

3 files changed, 29 insertions, 8 deletions

diff --git a/alembic/autogenerate/compare.py b/alembic/autogenerate/compare.py
index 693efae..5b69815 100644
--- a/alembic/autogenerate/compare.py
+++ b/alembic/autogenerate/compare.py
@@ -279,12 +279,22 @@ def _compare_tables(
                 upgrade_ops.ops.append(modify_table_ops)
 
 
-def _make_index(params: Dict[str, Any], conn_table: "Table") -> "Index":
+def _make_index(
+    params: Dict[str, Any], conn_table: "Table"
+) -> Optional["Index"]:
+    exprs = []
+    for col_name in params["column_names"]:
+        if col_name is None:
+            util.warn(
+                "Skipping reflected expression-based "
+                f"index {params['name']!r}"
+            )
+            return None
+        else:
+            item = conn_table.c[col_name]
+        exprs.append(item)
     ix = sa_schema.Index(
-        params["name"],
-        *[conn_table.c[cname] for cname in params["column_names"]],
-        unique=params["unique"],
-        _table=conn_table,
+        params["name"], *exprs, unique=params["unique"], _table=conn_table
     )
     if "duplicates_constraint" in params:
         ix.info["duplicates_constraint"] = params["duplicates_constraint"]
@@ -585,7 +595,9 @@ def _compare_indexes_and_uniques(
             )
 
         conn_indexes = set(  # type:ignore[assignment]
-            _make_index(ix, conn_table) for ix in conn_indexes
+            index
+            for index in (_make_index(ix, conn_table) for ix in conn_indexes)
+            if index is not None
         )
 
     # 2a. if the dialect dupes unique indexes as unique constraints
diff --git a/alembic/ddl/postgresql.py b/alembic/ddl/postgresql.py
index 019eb3c..5d93803 100644
--- a/alembic/ddl/postgresql.py
+++ b/alembic/ddl/postgresql.py
@@ -249,9 +249,13 @@ class PostgresqlImpl(DefaultImpl):
                 while isinstance(expr, UnaryExpression):
                     expr = expr.element
                 if not isinstance(expr, Column):
+                    if sqla_compat.sqla_2:
+                        msg = ""
+                    else:
+                        msg = "; not supported by SQLAlchemy reflection"
                     util.warn(
-                        "autogenerate skipping functional index %s; "
-                        "not supported by SQLAlchemy reflection" % idx.name
+                        "autogenerate skipping functional index "
+                        f"{idx.name!r}{msg}"
                     )
                     metadata_indexes.discard(idx)
 
diff --git a/alembic/testing/requirements.py b/alembic/testing/requirements.py
index 3947272..6896276 100644
--- a/alembic/testing/requirements.py
+++ b/alembic/testing/requirements.py
@@ -20,6 +20,11 @@ class SuiteRequirements(Requirements):
         return exclusions.closed()
 
     @property
+    def materialized_views(self):
+        """needed for sqlalchemy compat"""
+        return exclusions.closed()
+
+    @property
     def unique_constraint_reflection(self):
         def doesnt_have_check_uq_constraints(config):
             from sqlalchemy import inspect