fix: add new invariants module

datafusion/expr/src/logical_plan/invariants.rs

@@ -0,0 +1,60 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use datafusion_common::{
+    tree_node::TreeNodeRecursion, DFSchemaRef, DataFusionError, Result,
+};
+
+use super::LogicalPlan;
+
+/// Returns an error if plan, and subplans, do not have unique fields.
+///
+/// This invariant is subject to change.
+/// refer: <https://github.com/apache/datafusion/issues/13525#issuecomment-2494046463>
+pub fn assert_unique_field_names(plan: &LogicalPlan) -> Result<()> {
+    plan.schema().check_names()?;
+
+    plan.apply_with_subqueries(|plan: &LogicalPlan| {
+        plan.schema().check_names()?;
+        Ok(TreeNodeRecursion::Continue)
+    })
+    .map(|_| ())
+}
+
+/// Returns an error if the plan does not have the expected schema.
+/// Ignores metadata and nullability.
+pub fn assert_expected_schema(
+    rule_name: &str,
+    schema: &DFSchemaRef,
+    plan: &LogicalPlan,
+) -> Result<()> {
+    let equivalent = plan.schema().equivalent_names_and_types(schema);
+
+    if !equivalent {
+        let e = DataFusionError::Internal(format!(
+            "Failed due to a difference in schemas, original schema: {:?}, new schema: {:?}",
+            schema,
+            plan.schema()
+        ));
+        Err(DataFusionError::Context(
+            String::from(rule_name),
+            Box::new(e),
+        ))
+    } else {
+        Ok(())
+    }
+}