Fix CFG building error with parse errors in conditional branches

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

@@ -131,11 +131,12 @@ public ParseTree visitIfStatement(BSLParser.IfStatementContext ctx) {
 
     // тело true
     blocks.enterBlock();
-    if (ctx.ifBranch().codeBlock() != null) {
+    if (ctx.ifBranch().codeBlock() != null && !Trees.nodeContainsErrors(ctx.ifBranch())) {
       ctx.ifBranch().codeBlock().accept(this);
     }
     var truePart = blocks.leaveBlock();
 
+    graph.addVertex(truePart.begin());
     graph.addEdge(conditionStatement, truePart.begin(), CfgEdgeType.TRUE_BRANCH);
     currentLevelBlock.getBuildParts().push(truePart.end());
     currentLevelBlock.getBuildParts().push(conditionStatement);
@@ -198,9 +199,12 @@ public ParseTree visitElsifBranch(BSLParser.ElsifBranchContext ctx) {
 
     // тело true
     blocks.enterBlock();
-    ctx.codeBlock().accept(this);
+    if (ctx.codeBlock() != null && !Trees.nodeContainsErrors(ctx)) {
+      ctx.codeBlock().accept(this);
+    }
     var truePart = blocks.leaveBlock();
 
+    graph.addVertex(truePart.begin());
     graph.addEdge(condition, truePart.begin(), CfgEdgeType.TRUE_BRANCH);
     blocks.getCurrentBlock().getBuildParts().push(truePart.end());
     blocks.getCurrentBlock().getBuildParts().push(condition);
@@ -218,11 +222,14 @@ public ParseTree visitCodeBlock(BSLParser.CodeBlockContext ctx) {
   @Override
   public ParseTree visitElseBranch(BSLParser.ElseBranchContext ctx) {
     blocks.enterBlock();
-    ctx.codeBlock().accept(this);
+    if (ctx.codeBlock() != null && !Trees.nodeContainsErrors(ctx)) {
+      ctx.codeBlock().accept(this);
+    }
     var block = blocks.leaveBlock();
 
     // на стеке находится условие
     var condition = blocks.getCurrentBlock().getBuildParts().pop();
+    graph.addVertex(block.begin());
     graph.addEdge(condition, block.begin(), CfgEdgeType.FALSE_BRANCH);
     blocks.getCurrentBlock().getBuildParts().push(block.end());
 

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

@@ -0,0 +1,132 @@
+package com.github._1c_syntax.bsl.languageserver.cfg;
+
+import com.github._1c_syntax.bsl.languageserver.util.TestUtils;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest
+class CfgEmptyStringDotTest {
+
+  @Test
+  void testEmptyStringWithDotShouldNotCrash() {
+    var code = """
+      Процедура РаспределитьНаТовары(Команда)
+
+      Если Товар.ТаможеннаяСтоимость = "". Тогда
+
+      КонецЕсли;
+
+      КонецПроцедуры
+      """;
+
+    var dContext = TestUtils.getDocumentContext(code);
+    var parseTree = dContext.getAst().subs().sub(0).procedure().subCodeBlock().codeBlock();
+
+    var builder = new CfgBuildingParseTreeVisitor();
+    builder.producePreprocessorConditions(true);
+    builder.produceLoopIterations(false);
+    builder.determineAdjacentDeadCode(false);
+
+    // This should not crash
+    var graph = builder.buildGraph(parseTree);
+
+    // Basic validation that the graph was created
+    assertThat(graph).isNotNull();
+    assertThat(graph.getEntryPoint()).isNotNull();
+    assertThat(graph.getExitPoint()).isNotNull();
+  }
+
+  @Test
+  void testEmptyElsifBranchShouldNotCrash() {
+    var code = """
+      Процедура Тест()
+
+      Если Условие1 Тогда
+        Действие1();
+      ИначеЕсли Условие2 = "". Тогда
+
+      КонецЕсли;
+
+      КонецПроцедуры
+      """;
+
+    var dContext = TestUtils.getDocumentContext(code);
+    var parseTree = dContext.getAst().subs().sub(0).procedure().subCodeBlock().codeBlock();
+
+    var builder = new CfgBuildingParseTreeVisitor();
+    builder.producePreprocessorConditions(true);
+    builder.produceLoopIterations(false);
+    builder.determineAdjacentDeadCode(false);
+
+    // This should not crash
+    var graph = builder.buildGraph(parseTree);
+
+    // Basic validation that the graph was created
+    assertThat(graph).isNotNull();
+    assertThat(graph.getEntryPoint()).isNotNull();
+    assertThat(graph.getExitPoint()).isNotNull();
+  }
+
+  @Test
+  void testEmptyElseBranchShouldNotCrash() {
+    var code = """
+      Процедура Тест()
+
+      Если Условие1 Тогда
+        Действие1();
+      Иначе
+
+      КонецЕсли;
+
+      КонецПроцедуры
+      """;
+
+    var dContext = TestUtils.getDocumentContext(code);
+    var parseTree = dContext.getAst().subs().sub(0).procedure().subCodeBlock().codeBlock();
+
+    var builder = new CfgBuildingParseTreeVisitor();
+    builder.producePreprocessorConditions(true);
+    builder.produceLoopIterations(false);
+    builder.determineAdjacentDeadCode(false);
+
+    // This should not crash
+    var graph = builder.buildGraph(parseTree);
+
+    // Basic validation that the graph was created
+    assertThat(graph).isNotNull();
+    assertThat(graph.getEntryPoint()).isNotNull();
+    assertThat(graph.getExitPoint()).isNotNull();
+  }
+
+  @Test
+  void testOriginalIssueCase() {
+    // This is the exact code from the issue report
+    var code = """
+      Процедура Тест()
+
+      Если Товар.ТаможеннаяСтоимость = "". Тогда
+
+      КонецЕсли;
+
+      КонецПроцедуры
+      """;
+
+    var dContext = TestUtils.getDocumentContext(code);
+    var parseTree = dContext.getAst().subs().sub(0).procedure().subCodeBlock().codeBlock();
+
+    var builder = new CfgBuildingParseTreeVisitor();
+    builder.producePreprocessorConditions(true);
+    builder.produceLoopIterations(false);
+    builder.determineAdjacentDeadCode(false);
+
+    // This should not crash (was crashing before the fix)
+    var graph = builder.buildGraph(parseTree);
+
+    // Basic validation that the graph was created
+    assertThat(graph).isNotNull();
+    assertThat(graph.getEntryPoint()).isNotNull();
+    assertThat(graph.getExitPoint()).isNotNull();
+  }
+}