fix: handle null code blocks in loops

Author: seer-by-sentry[bot]

src/main/java/com/github/_1c_syntax/bsl/languageserver/cfg/CfgBuildingParseTreeVisitor.java

@@ -24,6 +24,7 @@
 import com.github._1c_syntax.bsl.parser.BSLParser;
 import com.github._1c_syntax.bsl.parser.BSLParserBaseVisitor;
 import com.github._1c_syntax.bsl.parser.BSLParserRuleContext;
+import jakarta.annotation.Nullable;
 import org.antlr.v4.runtime.tree.ParseTree;
 
 import java.util.ArrayList;
@@ -524,7 +525,7 @@ private void makeJump(CfgVertex jumpTarget) {
     graph.addVertex(blocks.getCurrentBlock().end());
   }
 
-  private void buildLoopSubgraph(BSLParser.CodeBlockContext ctx, LoopVertex loopStart) {
+  private void buildLoopSubgraph(@Nullable BSLParser.CodeBlockContext ctx, LoopVertex loopStart) {
     graph.addVertex(loopStart);
     connectGraphTail(blocks.getCurrentBlock(), loopStart);
 
@@ -537,7 +538,9 @@ private void buildLoopSubgraph(BSLParser.CodeBlockContext ctx, LoopVertex loopSt
 
     blocks.enterBlock(jumpState);
 
-    ctx.accept(this);
+    if (ctx != null) {
+      ctx.accept(this);
+    }
 
     var body = blocks.leaveBlock();
 

src/test/java/com/github/_1c_syntax/bsl/languageserver/cfg/ControlFlowGraphBuilderTest.java

@@ -451,6 +451,41 @@ void preprocessorIfWithElseBranching() {
     assertThat(walker.getCurrentNode()).isSameAs(lastStatement);
   }
 
+  @Test
+  void testLoopWithNullCodeBlock() {
+    var code = """
+      Для х = 1 По 10 Цикл
+        А = 1;
+      КонецЦикла;""";
+
+    var parseTree = parse(code);
+    
+    // Force null code block by removing the CodeBlock child
+    var forStatement = parseTree.statement(0).compoundStatement().forStatement();
+    var children = forStatement.children;
+    
+    // Find and remove the CodeBlockContext child
+    for (int i = 0; i < children.size(); i++) {
+      if (children.get(i) instanceof BSLParser.CodeBlockContext) {
+        children.remove(i);
+        break;
+      }
+    }
+
+    var builder = new CfgBuildingParseTreeVisitor();
+    var graph = builder.buildGraph(parseTree);
+
+    // Check if graph was built successfully
+    assertThat(graph).isNotNull();
+    assertThat(graph.vertexSet()).isNotEmpty();
+
+    // Verify basic structure - should at least have loop vertex and exit
+    var vertices = traverseToOrderedList(graph);
+    assertThat(vertices)
+      .hasAtLeastOneElementOfType(ForLoopVertex.class)
+      .hasAtLeastOneElementOfType(ExitVertex.class);
+  }
+
   @Test
   void preprocessorIfWithElseIfBranching() {
     var code = """