parser: improve error recovery for CTE (#683)

Author: sbdchd

crates/squawk_parser/src/grammar.rs

@@ -2511,7 +2511,11 @@ fn with_query_clause(p: &mut Parser<'_>) -> Option<CompletedMarker> {
             break;
         }
         if !p.eat(COMMA) {
-            break;
+            if p.at(IDENT) {
+                p.error("missing comma");
+            } else {
+                break;
+            }
         }
     }
     Some(m.complete(p, WITH_CLAUSE))

crates/squawk_parser/tests/data/err/select_cte.sql

@@ -12,3 +12,12 @@ select * from t order by ordercol;
 with t as (select 1)
 search depth first by a, b c set ordercol
 select * from t order by ordercol;
+
+with 
+   a as (
+      select 1
+   ) -- <-- missing a comma
+   b as (
+      select 3
+   )
+select 2;

crates/squawk_parser/tests/snapshots/tests__select_cte_err.snap

@@ -184,8 +184,62 @@ SOURCE_FILE
         NAME_REF
           IDENT "ordercol"
   SEMICOLON ";"
+  WHITESPACE "\n\n"
+  SELECT
+    WITH_CLAUSE
+      WITH_KW "with"
+      WHITESPACE " \n   "
+      WITH_TABLE
+        NAME
+          IDENT "a"
+        WHITESPACE " "
+        AS_KW "as"
+        WHITESPACE " "
+        L_PAREN "("
+        WHITESPACE "\n      "
+        SELECT
+          SELECT_CLAUSE
+            SELECT_KW "select"
+            WHITESPACE " "
+            TARGET_LIST
+              TARGET
+                LITERAL
+                  INT_NUMBER "1"
+        WHITESPACE "\n   "
+        R_PAREN ")"
+      WHITESPACE " "
+      COMMENT "-- <-- missing a comma"
+      WHITESPACE "\n   "
+      WITH_TABLE
+        NAME
+          IDENT "b"
+        WHITESPACE " "
+        AS_KW "as"
+        WHITESPACE " "
+        L_PAREN "("
+        WHITESPACE "\n      "
+        SELECT
+          SELECT_CLAUSE
+            SELECT_KW "select"
+            WHITESPACE " "
+            TARGET_LIST
+              TARGET
+                LITERAL
+                  INT_NUMBER "3"
+        WHITESPACE "\n   "
+        R_PAREN ")"
+    WHITESPACE "\n"
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          LITERAL
+            INT_NUMBER "2"
+  SEMICOLON ";"
   WHITESPACE "\n"
 ---
 ERROR@24: unexpected comma
 ERROR@140: unexpected comma, expected a column name
 ERROR@270: expected COMMA
+ERROR@357: missing comma