From 327b075d2049ec53fbae5b345fc9ae4018d50dcc Mon Sep 17 00:00:00 2001
From: Steve Dignam <steve@dignam.xyz>
Date: Thu, 19 Jun 2025 14:55:21 -0400
Subject: [PATCH] parser: fix crash with trailing comma

---
 crates/squawk_parser/src/grammar.rs           |  6 ++++-
 .../squawk_parser/tests/data/err/select.sql   |  3 +++
 .../tests/snapshots/tests__select_err.snap    | 24 ++++++++++++++++++-
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/crates/squawk_parser/src/grammar.rs b/crates/squawk_parser/src/grammar.rs
index 95a5b78a..c49bd0b2 100644
--- a/crates/squawk_parser/src/grammar.rs
+++ b/crates/squawk_parser/src/grammar.rs
@@ -4490,6 +4490,8 @@ const TARGET_FOLLOW: TokenSet = TokenSet::new(&[
     R_PAREN,
     R_BRACK,
     RETURNING_KW,
+    SEMICOLON,
+    EOF,
 ])
 .union(COMPOUND_SELECT_FIRST);
 
@@ -4547,7 +4549,7 @@ fn opt_target_list(p: &mut Parser) -> Option<CompletedMarker> {
     let m = p.start();
     while !p.at(EOF) && !p.at(SEMICOLON) {
         if opt_target_el(p).is_some() {
-            if p.at(COMMA) && matches!(p.nth(1), SEMICOLON | EOF) {
+            if p.at(COMMA) && p.nth_at_ts(1, TARGET_FOLLOW) {
                 p.err_and_bump("unexpected trailing comma");
                 break;
             }
@@ -4564,6 +4566,8 @@ fn opt_target_list(p: &mut Parser) -> Option<CompletedMarker> {
                     break;
                 }
             }
+        } else {
+            break;
         }
     }
     Some(m.complete(p, TARGET_LIST))
diff --git a/crates/squawk_parser/tests/data/err/select.sql b/crates/squawk_parser/tests/data/err/select.sql
index a039f4cf..59736be4 100644
--- a/crates/squawk_parser/tests/data/err/select.sql
+++ b/crates/squawk_parser/tests/data/err/select.sql
@@ -29,5 +29,8 @@ select numeric 1234;
 -- warns about a missing semicolon
 select select;
 
+-- extra comma
+select a, from t;
+
 -- trailing comma at EOF
 select 1,
diff --git a/crates/squawk_parser/tests/snapshots/tests__select_err.snap b/crates/squawk_parser/tests/snapshots/tests__select_err.snap
index 5cd7b14b..e104effd 100644
--- a/crates/squawk_parser/tests/snapshots/tests__select_err.snap
+++ b/crates/squawk_parser/tests/snapshots/tests__select_err.snap
@@ -223,6 +223,27 @@ SOURCE_FILE
       SELECT_KW "select"
   SEMICOLON ";"
   WHITESPACE "\n\n"
+  COMMENT "-- extra comma"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          NAME_REF
+            IDENT "a"
+        ERROR
+          COMMA ","
+    WHITESPACE " "
+    FROM_CLAUSE
+      FROM_KW "from"
+      WHITESPACE " "
+      FROM_ITEM
+        NAME_REF
+          IDENT "t"
+  SEMICOLON ";"
+  WHITESPACE "\n\n"
   COMMENT "-- trailing comma at EOF"
   WHITESPACE "\n"
   SELECT
@@ -248,4 +269,5 @@ ERROR@396: expected expression
 ERROR@397: expected expression
 ERROR@520: missing comma
 ERROR@646: expected SEMICOLON
-ERROR@689: unexpected trailing comma
+ERROR@679: unexpected trailing comma
+ERROR@723: unexpected trailing comma