fix(flow-php/postgresql): lower BulkInsert upsert with empty update set to ON CONFLICT DO NOTHING (#2452)

- prevents silent degradation to plain INSERT when all columns are
conflict columns

Author: norberttech

src/lib/postgresql/src/Flow/PostgreSql/QueryBuilder/Insert/BulkInsert.php

@@ -76,6 +76,10 @@ public function onConflictDoUpdate(ConflictTarget $target, ?array $updateColumns
             $assignments[$column] = 'EXCLUDED."' . $column . '"';
         }
 
+        if ($assignments === []) {
+            return new self($this->table, $this->columns, $this->rowCount, $target, true, []);
+        }
+
         return new self($this->table, $this->columns, $this->rowCount, $target, false, $assignments);
     }
 

src/lib/postgresql/tests/Flow/PostgreSql/Tests/Unit/QueryBuilder/Insert/BulkInsertTest.php

@@ -149,6 +149,51 @@ public function test_on_conflict_do_update_with_all_non_conflict_columns(): void
         );
     }
 
+    public function test_on_conflict_do_update_with_all_columns_as_conflict_target_emits_do_nothing(): void
+    {
+        $query = BulkInsert::into('t', ['a', 'b'], 1)->onConflictDoUpdate(ConflictTarget::columns(['a', 'b']));
+
+        static::assertSame(
+            'INSERT INTO "t" ("a", "b") VALUES ($1, $2) ON CONFLICT ("a", "b") DO NOTHING',
+            $query->toSql(),
+        );
+    }
+
+    public function test_on_conflict_do_update_with_constraint_and_empty_update_columns_emits_do_nothing(): void
+    {
+        $query = BulkInsert::into('t', ['a', 'b'], 1)->onConflictDoUpdate(ConflictTarget::constraint('t_pkey'), []);
+
+        static::assertSame(
+            'INSERT INTO "t" ("a", "b") VALUES ($1, $2) ON CONFLICT ON CONSTRAINT "t_pkey" DO NOTHING',
+            $query->toSql(),
+        );
+    }
+
+    public function test_on_conflict_do_update_with_empty_update_columns_emits_do_nothing(): void
+    {
+        $query = BulkInsert::into('users', ['email', 'name'], 1)->onConflictDoUpdate(
+            ConflictTarget::columns(['email']),
+            [],
+        );
+
+        static::assertSame(
+            'INSERT INTO "users" ("email", "name") VALUES ($1, $2) ON CONFLICT ("email") DO NOTHING',
+            $query->toSql(),
+        );
+    }
+
+    public function test_on_conflict_do_update_with_subset_target_still_emits_do_update(): void
+    {
+        $query = BulkInsert::into('users', ['email', 'name'], 1)->onConflictDoUpdate(ConflictTarget::columns([
+            'email',
+        ]));
+
+        static::assertSame(
+            'INSERT INTO "users" ("email", "name") VALUES ($1, $2) ON CONFLICT ("email") DO UPDATE SET "name" = EXCLUDED."name"',
+            $query->toSql(),
+        );
+    }
+
     public function test_on_conflict_do_update_with_constraint(): void
     {
         $query = BulkInsert::into('users', ['email', 'name'], 1)->onConflictDoUpdate(