fix: avoid recursion when deparsing statement lists (#2651)

Author: minleejae

src/main/java/net/sf/jsqlparser/statement/Block.java

@@ -9,6 +9,8 @@
  */
 package net.sf.jsqlparser.statement;
 
+import java.util.function.Consumer;
+
 public class Block implements Statement {
     private boolean hasSemicolonAfterEnd = false;
 
@@ -36,9 +38,13 @@ public <T, S> T accept(StatementVisitor<T> statementVisitor, S context) {
     }
 
     public StringBuilder appendTo(StringBuilder builder) {
+        return appendTo(builder, builder::append);
+    }
+
+    public StringBuilder appendTo(StringBuilder builder, Consumer<Statements> statementsPrinter) {
         builder.append("BEGIN\n");
         if (statements != null) {
-            builder.append(statements);
+            statementsPrinter.accept(statements);
         }
         builder.append("END");
         if (hasSemicolonAfterEnd) {

src/main/java/net/sf/jsqlparser/statement/IfElseStatement.java

@@ -11,6 +11,7 @@
 package net.sf.jsqlparser.statement;
 
 import java.util.Objects;
+import java.util.function.Consumer;
 
 import net.sf.jsqlparser.expression.Expression;
 
@@ -65,12 +66,21 @@ public void setUsingSemicolonForIfStatement(boolean usingSemicolonForIfStatement
     }
 
     public StringBuilder appendTo(StringBuilder builder) {
-        builder.append("IF ").append(condition).append(" ").append(ifStatement)
-                .append(usingSemicolonForIfStatement ? ";" : "");
+        return appendTo(builder, builder::append, builder::append);
+    }
+
+    public StringBuilder appendTo(StringBuilder builder, Consumer<Expression> expressionPrinter,
+            Consumer<Statement> statementPrinter) {
+        builder.append("IF ");
+        expressionPrinter.accept(condition);
+        builder.append(' ');
+        statementPrinter.accept(ifStatement);
+        builder.append(usingSemicolonForIfStatement ? ";" : "");
 
         if (elseStatement != null) {
-            builder.append(" ELSE ").append(elseStatement)
-                    .append(usingSemicolonForElseStatement ? ";" : "");
+            builder.append(" ELSE ");
+            statementPrinter.accept(elseStatement);
+            builder.append(usingSemicolonForElseStatement ? ";" : "");
         }
         return builder;
     }

src/main/java/net/sf/jsqlparser/statement/Statements.java

@@ -12,6 +12,7 @@
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.Consumer;
 
 public class Statements extends ArrayList<Statement> implements Serializable {
 
@@ -34,17 +35,30 @@ public <E extends Statement> E get(Class<E> type, int index) {
         return type.cast(get(index));
     }
 
-    @Override
-    public String toString() {
-        StringBuilder b = new StringBuilder();
+    /**
+     * Appends each statement using the supplied renderer and the list's separators. Blocks and
+     * IF/ELSE statements retain their own semicolon settings. Null entries produced by error
+     * recovery retain the legacy "null;" placeholder without invoking the renderer.
+     */
+    public StringBuilder appendTo(StringBuilder builder, Consumer<Statement> statementPrinter) {
         for (Statement stmt : this) {
-            // IfElseStatements and Blocks control the Semicolons by themselves
-            if (stmt instanceof IfElseStatement || stmt instanceof Block) {
-                b.append(stmt).append("\n");
+            if (stmt == null) {
+                builder.append("null");
             } else {
-                b.append(stmt).append(";\n");
+                statementPrinter.accept(stmt);
+            }
+            // IfElseStatements and Blocks control the Semicolons by themselves
+            if (!(stmt instanceof IfElseStatement || stmt instanceof Block)) {
+                builder.append(';');
             }
+            builder.append('\n');
         }
-        return b.toString();
+        return builder;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        return appendTo(builder, builder::append).toString();
     }
 }

src/main/java/net/sf/jsqlparser/util/deparser/StatementDeParser.java

@@ -344,8 +344,7 @@ public <S> StringBuilder visit(AlterEvent alterEvent, S context) {
 
     @Override
     public <S> StringBuilder visit(Statements statements, S context) {
-        statements.accept(this, context);
-        return builder;
+        return statements.appendTo(builder, statement -> statement.accept(this, context));
     }
 
     @Override
@@ -435,18 +434,7 @@ public <S> StringBuilder visit(ShowTablesStatement showTables, S context) {
 
     @Override
     public <S> StringBuilder visit(Block block, S context) {
-        builder.append("BEGIN\n");
-        if (block.getStatements() != null) {
-            for (Statement stmt : block.getStatements()) {
-                stmt.accept(this, context);
-                builder.append(";\n");
-            }
-        }
-        builder.append("END");
-        if (block.hasSemicolonAfterEnd()) {
-            builder.append(";");
-        }
-        return builder;
+        return block.appendTo(builder, statements -> statements.accept(this, context));
     }
 
     @Override
@@ -563,8 +551,9 @@ public <S> StringBuilder visit(AlterSession alterSession, S context) {
 
     @Override
     public <S> StringBuilder visit(IfElseStatement ifElseStatement, S context) {
-        ifElseStatement.appendTo(builder);
-        return builder;
+        return ifElseStatement.appendTo(builder,
+                expression -> expression.accept(expressionDeParser, context),
+                statement -> statement.accept(this, context));
     }
 
     @Override

src/site/sphinx/usage.rst

@@ -690,6 +690,20 @@ The object model works in both directions. Build the tree from Java and print it
 
     Assertions.assertEquals(expectedSQLStr, builder.toString());
 
+The same visitor can render an entire statement list:
+
+.. code-block:: java
+
+    Statements statements = CCJSqlParserUtil.parseStatements("SELECT 1; SELECT 2;");
+    StringBuilder script = new StringBuilder();
+    statements.accept(new StatementDeParser(script), null);
+    Assertions.assertEquals("SELECT 1;\nSELECT 2;\n", script.toString());
+
+Statement lists and nested blocks share the separator policy used by
+``Statements.toString()``. Blocks and ``IF/ELSE`` statements retain their own
+semicolon settings. Custom deparsers receive each child statement and the
+``IF/ELSE`` condition through the visitor API, with the supplied context.
+
 
 ODBC timestamp intervals
 ==============================