Fix parseStatements failure propagation and executor cleanup (#2568)

Author: minleejae

src/main/java/net/sf/jsqlparser/parser/CCJSqlParserUtil.java

@@ -429,10 +429,11 @@ public static Statements parseStatements(String sqls, Consumer<CCJSqlParser> con
         }
 
         ExecutorService executorService = Executors.newSingleThreadExecutor();
-        final Statements statements = parseStatements(sqls, executorService, consumer);
-        executorService.shutdown();
-
-        return statements;
+        try {
+            return parseStatements(sqls, executorService, consumer);
+        } finally {
+            executorService.shutdown();
+        }
     }
 
     /**
@@ -447,7 +448,6 @@ public static Statements parseStatements(String sqls, ExecutorService executorSe
             return null;
         }
 
-        Statements statements = null;
         CCJSqlParser parser = newParser(sqls);
         if (consumer != null) {
             consumer.accept(parser);
@@ -457,7 +457,7 @@ public static Statements parseStatements(String sqls, ExecutorService executorSe
 
         // first, try to parse fast and simple
         try {
-            statements = parseStatements(parser.withAllowComplexParsing(false), executorService);
+            return parseStatements(parser.withAllowComplexParsing(false), executorService);
         } catch (JSQLParserException ex) {
             // when fast simple parsing fails, try complex parsing but only if it has a chance to
             // succeed
@@ -468,10 +468,10 @@ public static Statements parseStatements(String sqls, ExecutorService executorSe
                 if (consumer != null) {
                     consumer.accept(parser);
                 }
-                statements = parseStatements(parser.withAllowComplexParsing(true), executorService);
+                return parseStatements(parser.withAllowComplexParsing(true), executorService);
             }
+            throw ex;
         }
-        return statements;
     }
 
     /**

src/test/java/net/sf/jsqlparser/parser/ParseStatementsFailureTest.java

@@ -0,0 +1,81 @@
+/*-
+ * #%L
+ * JSQLParser library
+ * %%
+ * Copyright (C) 2004 - 2026 JSQLParser
+ * %%
+ * Dual licensed under GNU LGPL 2.1 or Apache License 2.0
+ * #L%
+ */
+package net.sf.jsqlparser.parser;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.statement.UnsupportedStatement;
+import org.junit.jupiter.api.Test;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ParseStatementsFailureTest {
+    @Test
+    void reportsFailureWhenComplexParsingIsDisabled() {
+        JSQLParserException exception = assertThrows(JSQLParserException.class,
+                () -> CCJSqlParserUtil.parseStatements("SELECT FROM",
+                        parser -> parser.withAllowComplexParsing(false)));
+        assertNotNull(exception.getCause());
+    }
+
+    @Test
+    void reportsFailureWhenNestingPreventsRetry() {
+        assertThrows(JSQLParserException.class,
+                () -> CCJSqlParserUtil.parseStatements("SELECT (( FROM",
+                        parser -> parser.withAllowComplexParsing(true).withAllowedNestingDepth(0)));
+    }
+
+    @Test
+    void leavesCallerExecutorUsableAfterFailure() throws Exception {
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+        try {
+            assertThrows(JSQLParserException.class,
+                    () -> CCJSqlParserUtil.parseStatements("SELECT FROM", executor,
+                            parser -> parser.withAllowComplexParsing(false)));
+            assertFalse(executor.isShutdown());
+            assertEquals(2, CCJSqlParserUtil.parseStatements("SELECT 1; SELECT 2", executor,
+                    parser -> parser.withAllowComplexParsing(false)).size());
+        } finally {
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    void reportsTimeoutWhenComplexParsingIsDisabled() {
+        ExecutorService executor = Executors.newSingleThreadExecutor();
+        CountDownLatch release = new CountDownLatch(1);
+        executor.submit(() -> release.await(30, TimeUnit.SECONDS));
+        try {
+            JSQLParserException exception = assertThrows(JSQLParserException.class,
+                    () -> CCJSqlParserUtil.parseStatements("SELECT 1", executor,
+                            parser -> parser.withAllowComplexParsing(false).withTimeOut(50)));
+            assertInstanceOf(TimeoutException.class, exception.getCause());
+        } finally {
+            release.countDown();
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    void preservesEmptyInputAndUnsupportedStatementContracts() throws Exception {
+        assertNull(CCJSqlParserUtil.parseStatements((String) null));
+        assertNull(CCJSqlParserUtil.parseStatements(""));
+        assertInstanceOf(UnsupportedStatement.class,
+                CCJSqlParserUtil.parseStatements("SELECT 1; WHATEVER !",
+                        parser -> parser.withAllowComplexParsing(false)
+                                .withUnsupportedStatements(true))
+                        .get(1));
+    }
+}