Allow safe Cypher reserved keywords in alias positions (#2355)

Makefile

@@ -177,7 +177,8 @@ REGRESS = scan \
           predicate_functions \
           map_projection \
           direct_field_access \
-          security
+          security \
+          reserved_keyword_alias
 
 ifneq ($(EXTRA_TESTS),)
   REGRESS += $(EXTRA_TESTS)

regress/expected/reserved_keyword_alias.out

@@ -0,0 +1,248 @@
+/*
+ * 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.
+ */
+/*
+ * Regression coverage for issue #2355:
+ *   Cypher reserved keywords from the `safe_keywords` set must be accepted
+ *   in alias positions (RETURN/WITH/YIELD ... AS <name>, UNWIND ... AS <name>).
+ *   Conflicting tokens (END / NULL / TRUE / FALSE) must remain rejected.
+ *   Pattern variable bindings are intentionally still restricted to plain
+ *   identifiers.
+ */
+LOAD 'age';
+SET search_path TO ag_catalog;
+SELECT * FROM create_graph('issue_2355');
+NOTICE:  graph "issue_2355" has been created
+ create_graph 
+--------------
+
+(1 row)
+
+-- The exact reproducer from the issue (previously failed with
+-- "syntax error at or near "count"").
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS count $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+-- Representative coverage across the safe_keywords set as RETURN aliases.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS exists      $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS coalesce    $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS match       $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS return      $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS where       $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS order       $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS limit       $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS distinct    $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS optional    $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS detach      $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS contains    $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS starts      $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS ends        $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS in          $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS is          $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS not         $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS yield       $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS call        $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+-- Multiple keyword aliases in one projection.
+SELECT * FROM cypher('issue_2355',
+    $$ RETURN 1 AS count, 2 AS exists, 3 AS where $$
+) AS (count agtype, ex agtype, w agtype);
+ count | ex | w 
+-------+----+---
+ 1     | 2  | 3
+(1 row)
+
+-- WITH ... AS <safe_keyword>: alias binding works.
+SELECT * FROM cypher('issue_2355',
+    $$ WITH 1 AS count RETURN 1 AS x $$
+) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+-- UNWIND ... AS <safe_keyword>: alias binding works.
+SELECT * FROM cypher('issue_2355',
+    $$ UNWIND [1, 2, 3] AS row RETURN 1 AS x $$
+) AS (a agtype);
+ a 
+---
+ 1
+ 1
+ 1
+(3 rows)
+
+-- conflicted_keywords (END, NULL, TRUE, FALSE) MUST still be rejected
+-- because they introduce real grammar ambiguity with literal/expression
+-- productions.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS null  $$) AS (a agtype);
+ERROR:  syntax error at or near "null"
+LINE 1: SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS null  $$) ...
+                                                          ^
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS true  $$) AS (a agtype);
+ERROR:  syntax error at or near "true"
+LINE 1: SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS true  $$) ...
+                                                          ^
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS false $$) AS (a agtype);
+ERROR:  syntax error at or near "false"
+LINE 1: SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS false $$) ...
+                                                          ^
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS end   $$) AS (a agtype);
+ERROR:  syntax error at or near "end"
+LINE 1: SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS end   $$) ...
+                                                          ^
+-- Pattern-variable positions are intentionally NOT broadened (would
+-- create shift/reduce conflicts). Confirm they still error.
+SELECT * FROM cypher('issue_2355',
+    $$ MATCH (count) RETURN 1 AS x $$
+) AS (a agtype);
+ERROR:  syntax error at or near "count"
+LINE 2:     $$ MATCH (count) RETURN 1 AS x $$
+                      ^
+-- Plain identifiers naturally remain unaffected.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS my_alias $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+-- Backtick-quoted alias positive case: forces the IDENTIFIER token
+-- path, so future grammar refactors don't accidentally regress quoted
+-- identifiers when the unquoted form is also a keyword.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS `count` $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+SELECT * FROM cypher('issue_2355', $$ WITH 1 AS `count` RETURN `count` $$) AS (a agtype);
+ a 
+---
+ 1
+(1 row)
+
+-- Known limitation: reading a keyword-named alias back fails because
+-- expr_var reads through var_name (which is unchanged here). Tracked
+-- in issue #2416. Captured in the expected output so the next
+-- contributor who fixes expr_var has a precise file to update.
+SELECT * FROM cypher('issue_2355', $$ WITH 1 AS count RETURN count $$) AS (a agtype);
+ERROR:  syntax error at end of input
+LINE 1: ...her('issue_2355', $$ WITH 1 AS count RETURN count $$) AS (a ...
+                                                             ^
+SELECT * FROM drop_graph('issue_2355', true);
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to table issue_2355._ag_label_vertex
+drop cascades to table issue_2355._ag_label_edge
+NOTICE:  graph "issue_2355" has been dropped
+ drop_graph 
+------------
+
+(1 row)
+

regress/sql/reserved_keyword_alias.sql

@@ -0,0 +1,102 @@
+/*
+ * 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.
+ */
+
+/*
+ * Regression coverage for issue #2355:
+ *   Cypher reserved keywords from the `safe_keywords` set must be accepted
+ *   in alias positions (RETURN/WITH/YIELD ... AS <name>, UNWIND ... AS <name>).
+ *   Conflicting tokens (END / NULL / TRUE / FALSE) must remain rejected.
+ *   Pattern variable bindings are intentionally still restricted to plain
+ *   identifiers.
+ */
+
+LOAD 'age';
+SET search_path TO ag_catalog;
+
+SELECT * FROM create_graph('issue_2355');
+
+-- The exact reproducer from the issue (previously failed with
+-- "syntax error at or near "count"").
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS count $$) AS (a agtype);
+
+-- Representative coverage across the safe_keywords set as RETURN aliases.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS exists      $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS coalesce    $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS match       $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS return      $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS where       $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS order       $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS limit       $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS distinct    $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS optional    $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS detach      $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS contains    $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS starts      $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS ends        $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS in          $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS is          $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS not         $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS yield       $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS call        $$) AS (a agtype);
+
+-- Multiple keyword aliases in one projection.
+SELECT * FROM cypher('issue_2355',
+    $$ RETURN 1 AS count, 2 AS exists, 3 AS where $$
+) AS (count agtype, ex agtype, w agtype);
+
+-- WITH ... AS <safe_keyword>: alias binding works.
+SELECT * FROM cypher('issue_2355',
+    $$ WITH 1 AS count RETURN 1 AS x $$
+) AS (a agtype);
+
+-- UNWIND ... AS <safe_keyword>: alias binding works.
+SELECT * FROM cypher('issue_2355',
+    $$ UNWIND [1, 2, 3] AS row RETURN 1 AS x $$
+) AS (a agtype);
+
+-- conflicted_keywords (END, NULL, TRUE, FALSE) MUST still be rejected
+-- because they introduce real grammar ambiguity with literal/expression
+-- productions.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS null  $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS true  $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS false $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS end   $$) AS (a agtype);
+
+-- Pattern-variable positions are intentionally NOT broadened (would
+-- create shift/reduce conflicts). Confirm they still error.
+SELECT * FROM cypher('issue_2355',
+    $$ MATCH (count) RETURN 1 AS x $$
+) AS (a agtype);
+
+-- Plain identifiers naturally remain unaffected.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS my_alias $$) AS (a agtype);
+
+-- Backtick-quoted alias positive case: forces the IDENTIFIER token
+-- path, so future grammar refactors don't accidentally regress quoted
+-- identifiers when the unquoted form is also a keyword.
+SELECT * FROM cypher('issue_2355', $$ RETURN 1 AS `count` $$) AS (a agtype);
+SELECT * FROM cypher('issue_2355', $$ WITH 1 AS `count` RETURN `count` $$) AS (a agtype);
+
+-- Known limitation: reading a keyword-named alias back fails because
+-- expr_var reads through var_name (which is unchanged here). Tracked
+-- in issue #2416. Captured in the expected output so the next
+-- contributor who fixes expr_var has a precise file to update.
+SELECT * FROM cypher('issue_2355', $$ WITH 1 AS count RETURN count $$) AS (a agtype);
+
+SELECT * FROM drop_graph('issue_2355', true);