Render if_not_exists option for CreateIndexOp and DropIndexOp

Fixes: sqlalchemy#151

alembic/autogenerate/render.py

@@ -324,6 +324,8 @@ def _add_index(autogen_context: AutogenContext, op: ops.CreateIndexOp) -> str:
     assert index.table is not None
 
     opts = _render_dialect_kwargs_items(autogen_context, index)
+    if op.if_not_exists is not None:
+        opts.append("if_not_exists=%r" % bool(op.if_not_exists))
     text = tmpl % {
         "prefix": _alembic_autogenerate_prefix(autogen_context),
         "name": _render_gen_name(autogen_context, index.name),
@@ -356,6 +358,8 @@ def _drop_index(autogen_context: AutogenContext, op: ops.DropIndexOp) -> str:
             "table_name=%(table_name)r%(schema)s%(kwargs)s)"
         )
     opts = _render_dialect_kwargs_items(autogen_context, index)
+    if op.if_exists is not None:
+        opts.append("if_exists=%r" % bool(op.if_exists))
     text = tmpl % {
         "prefix": _alembic_autogenerate_prefix(autogen_context),
         "name": _render_gen_name(autogen_context, op.index_name),

docs/build/unreleased/1446.rst

@@ -0,0 +1,6 @@
+.. change::
+    :tags: usecase, autogenerate
+    :tickets: 151
+
+    Render `if_exists` and `if_not_exists` in `CreateIndexOp` and `DropIndexOp` in autogenerate context.
+    Pull request courtesy of Louis-Amaury Chaib

tests/test_autogen_render.py

@@ -93,6 +93,20 @@ def test_render_add_index(self):
             "['active', 'code'], unique=False)",
         )
 
+    def test_render_add_index_if_not_exists(self):
+        """
+        autogenerate.render._add_index
+        """
+        t = self.table()
+        idx = Index("test_active_code_idx", t.c.active, t.c.code)
+        op_obj = ops.CreateIndexOp.from_index(idx)
+        op_obj.if_not_exists = True
+        eq_ignore_whitespace(
+            autogenerate.render_op_text(self.autogen_context, op_obj),
+            "op.create_index('test_active_code_idx', 'test', "
+            "['active', 'code'], unique=False, if_not_exists=True)",
+        )
+
     @testing.emits_warning("Can't validate argument ")
     def test_render_add_index_custom_kwarg(self):
         t = self.table()
@@ -212,6 +226,20 @@ def test_drop_index(self):
             "op.drop_index('test_active_code_idx', table_name='test')",
         )
 
+    def test_drop_index_if_exists(self):
+        """
+        autogenerate.render._drop_index
+        """
+        t = self.table()
+        idx = Index("test_active_code_idx", t.c.active, t.c.code)
+        op_obj = ops.DropIndexOp.from_index(idx)
+        op_obj.if_exists = True
+        eq_ignore_whitespace(
+            autogenerate.render_op_text(self.autogen_context, op_obj),
+            "op.drop_index('test_active_code_idx', table_name='test', "
+            "if_exists=True)",
+        )
+
     def test_drop_index_text(self):
         """
         autogenerate.render._drop_index