fix(parser): pass modifier to ExceptOp/MinusOp constructors and reset between iterations

EXCEPT ALL/DISTINCT and MINUS ALL/DISTINCT modifiers were silently
dropped during parsing because the grammar captured the modifier via
SetOperationModifier() but constructed ExceptOp and MinusOp with
their no-arg constructors (defaulting to empty string), unlike
UnionOp and IntersectOp which correctly received the modifier.

Additionally, the modifier variable was not reset between iterations
of the set-operation loop, causing modifiers to leak from one
operator to the next (e.g., UNION ALL ... EXCEPT would incorrectly
make the EXCEPT inherit ALL).

Fixes #2419

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: queelius

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -5093,7 +5093,7 @@ Select SetOperationList(Select select) #SetOperationList: {
         selects.add(select);
     }
 
-    ( LOOKAHEAD(2) (
+    ( LOOKAHEAD(2) { modifier = null; } (
             (
                 <K_UNION> [ modifier=SetOperationModifier() ] { UnionOp union = new UnionOp(modifier); linkAST(union,jjtThis); operations.add(union); }
 
@@ -5104,11 +5104,11 @@ Select SetOperationList(Select select) #SetOperationList: {
             )
             |
             (
-                <K_MINUS> [ modifier=SetOperationModifier() ] { MinusOp minus = new MinusOp(); linkAST(minus,jjtThis); operations.add(minus); }
+                <K_MINUS> [ modifier=SetOperationModifier() ] { MinusOp minus = new MinusOp(modifier); linkAST(minus,jjtThis); operations.add(minus); }
             )
             |
             (
-                <K_EXCEPT> [ modifier=SetOperationModifier() ] { ExceptOp except = new ExceptOp(); linkAST(except,jjtThis); operations.add(except); }
+                <K_EXCEPT> [ modifier=SetOperationModifier() ] { ExceptOp except = new ExceptOp(modifier); linkAST(except,jjtThis); operations.add(except); }
             )
 
         )

src/test/java/net/sf/jsqlparser/statement/select/SetOperationModifierTest.java

@@ -0,0 +1,132 @@
+/*-
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2019 JSQLParser
+ * %%
+ * Dual licensed under GNU LGPL 2.1 or Apache License 2.0
+ * #L%
+ */
+package net.sf.jsqlparser.statement.select;
+
+import static net.sf.jsqlparser.test.TestUtils.assertSqlCanBeParsedAndDeparsed;
+import static org.junit.jupiter.api.Assertions.*;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.statement.Statement;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.parallel.Execution;
+import org.junit.jupiter.api.parallel.ExecutionMode;
+
+/**
+ * Regression tests for EXCEPT/MINUS ALL/DISTINCT modifier handling.
+ * <p>
+ * Verifies that the ALL and DISTINCT modifiers are correctly preserved during
+ * parse-toString round-trips for all set operation types: UNION, INTERSECT,
+ * EXCEPT, and MINUS.
+ *
+ * @see <a href="https://github.com/JSQLParser/JSqlParser/issues/2080">#2080</a>
+ */
+@Execution(ExecutionMode.CONCURRENT)
+public class SetOperationModifierTest {
+
+    // ── EXCEPT modifier tests ─────────────────────────────────────
+
+    @Test
+    public void testExceptAllRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 EXCEPT ALL SELECT a FROM t2");
+    }
+
+    @Test
+    public void testExceptDistinctRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 EXCEPT DISTINCT SELECT a FROM t2");
+    }
+
+    @Test
+    public void testPlainExceptRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 EXCEPT SELECT a FROM t2");
+    }
+
+    // ── MINUS modifier tests ─────────────────────────────────────
+
+    @Test
+    public void testMinusAllRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 MINUS ALL SELECT a FROM t2");
+    }
+
+    @Test
+    public void testMinusDistinctRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 MINUS DISTINCT SELECT a FROM t2");
+    }
+
+    @Test
+    public void testPlainMinusRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 MINUS SELECT a FROM t2");
+    }
+
+    // ── Cross-check: UNION and INTERSECT still work ──────────────
+
+    @Test
+    public void testUnionAllRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 UNION ALL SELECT a FROM t2");
+    }
+
+    @Test
+    public void testIntersectAllRoundTrip() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT a FROM t1 INTERSECT ALL SELECT a FROM t2");
+    }
+
+    // ── Modifier leak prevention: modifiers must not bleed across operators ──
+
+    @Test
+    public void testModifierDoesNotLeakFromUnionAllToExcept() throws JSQLParserException {
+        String sql = "SELECT a FROM t1 UNION ALL SELECT b FROM t2 EXCEPT SELECT c FROM t3";
+        Statement stmt = CCJSqlParserUtil.parse(sql);
+        String result = stmt.toString();
+        // EXCEPT must NOT inherit ALL from the preceding UNION ALL
+        assertFalse(result.contains("EXCEPT ALL"),
+                "Modifier should not leak from UNION ALL to a subsequent plain EXCEPT: " + result);
+    }
+
+    @Test
+    public void testModifierDoesNotLeakFromIntersectAllToUnion() throws JSQLParserException {
+        String sql = "SELECT a FROM t1 INTERSECT ALL SELECT b FROM t2 UNION SELECT c FROM t3";
+        Statement stmt = CCJSqlParserUtil.parse(sql);
+        String result = stmt.toString();
+        assertFalse(result.contains("UNION ALL"),
+                "Modifier should not leak from INTERSECT ALL to a subsequent plain UNION: " + result);
+    }
+
+    @Test
+    public void testMixedModifiersPreserved() throws JSQLParserException {
+        // UNION ALL followed by EXCEPT DISTINCT
+        assertSqlCanBeParsedAndDeparsed(
+                "SELECT a FROM t1 UNION ALL SELECT b FROM t2 EXCEPT DISTINCT SELECT c FROM t3");
+    }
+
+    // ── SetOperation object state verification ──────────────────
+
+    @Test
+    public void testExceptAllSetOperationObject() throws JSQLParserException {
+        String sql = "SELECT a FROM t1 EXCEPT ALL SELECT a FROM t2";
+        Statement stmt = CCJSqlParserUtil.parse(sql);
+        SetOperationList setOpList = (SetOperationList) stmt;
+        SetOperation op = setOpList.getOperation(0);
+
+        assertInstanceOf(ExceptOp.class, op);
+        assertTrue(op.isAll(), "ExceptOp should report isAll() == true");
+        assertFalse(op.isDistinct(), "ExceptOp should report isDistinct() == false");
+    }
+
+    @Test
+    public void testMinusAllSetOperationObject() throws JSQLParserException {
+        String sql = "SELECT a FROM t1 MINUS ALL SELECT a FROM t2";
+        Statement stmt = CCJSqlParserUtil.parse(sql);
+        SetOperationList setOpList = (SetOperationList) stmt;
+        SetOperation op = setOpList.getOperation(0);
+
+        assertInstanceOf(MinusOp.class, op);
+        assertTrue(op.isAll(), "MinusOp should report isAll() == true");
+    }
+}