do not generate duplicated constructors, warn when nothing was added (IDEA-67659)

java/java-impl/src/com/intellij/codeInsight/generation/GenerateConstructorHandler.java

@@ -161,9 +161,22 @@ public class GenerateConstructorHandler extends GenerateMembersHandlerBase {
         }
         constructors.add(new PsiGenerationInfo(generateConstructorPrototype(aClass, baseConstructor, myCopyJavadoc, fields)));
       }
-      return constructors;
+      return filterOutAlreadyInsertedConstructors(aClass, constructors);
     }
-    return Collections.<GenerationInfo>singletonList(new PsiGenerationInfo(generateConstructorPrototype(aClass, null, false, fields)));
+    final List<GenerationInfo> constructors =
+      Collections.<GenerationInfo>singletonList(new PsiGenerationInfo(generateConstructorPrototype(aClass, null, false, fields)));
+    return filterOutAlreadyInsertedConstructors(aClass, constructors);
+  }
+
+  private static List<? extends GenerationInfo> filterOutAlreadyInsertedConstructors(PsiClass aClass, List<? extends GenerationInfo> constructors) {
+    boolean alreadyExist = true;
+    for (GenerationInfo constructor : constructors) {
+      alreadyExist &= aClass.findMethodBySignature((PsiMethod)constructor.getPsiMember(), false) != null;
+    }
+    if (alreadyExist) {
+      return Collections.emptyList();
+    }
+    return constructors;
   }
 
   public static PsiMethod generateConstructorPrototype(PsiClass aClass, PsiMethod baseConstructor, boolean copyJavaDoc, PsiField[] fields) throws IncorrectOperationException {
@@ -172,6 +185,7 @@ public class GenerateConstructorHandler extends GenerateMembersHandlerBase {
     CodeStyleManager codeStyleManager = CodeStyleManager.getInstance(manager.getProject());
 
     PsiMethod constructor = factory.createConstructor();
+    constructor.setName(aClass.getName());
     @Modifier String modifier = getConstructorModifier(aClass);
     if (modifier != null) {
       PsiUtil.setModifierProperty(constructor, modifier, true);

java/java-impl/src/com/intellij/codeInsight/generation/GenerateMembersHandlerBase.java

@@ -16,6 +16,7 @@
 package com.intellij.codeInsight.generation;
 
 import com.intellij.codeInsight.CodeInsightActionHandler;
+import com.intellij.codeInsight.hint.HintManager;
 import com.intellij.codeInsight.template.Template;
 import com.intellij.codeInsight.template.TemplateEditingAdapter;
 import com.intellij.codeInsight.template.TemplateManager;
@@ -114,10 +115,16 @@ public abstract class GenerateMembersHandlerBase implements CodeInsightActionHan
       LOG.error(e);
       return;
     }
-    if (newMembers.isEmpty()) return;
 
     editor.getCaretModel().moveToLogicalPosition(new LogicalPosition(line, col));
 
+    if (newMembers.isEmpty()) {
+      if (!ApplicationManager.getApplication().isUnitTestMode()) {
+        HintManager.getInstance().showErrorHint(editor, "Nothing found to insert");
+      }
+      return;
+    }
+
     final ArrayList<TemplateGenerationInfo> templates = new ArrayList<TemplateGenerationInfo>();
     for (GenerationInfo member : newMembers) {
       if (member instanceof TemplateGenerationInfo) {

java/java-tests/testData/codeInsight/generateConstructor/afterNoMoreConstructorsCanBeGenerated.java

@@ -0,0 +1,6 @@
+public class Test {
+  <caret>
+
+  public Test() {
+  }
+}

java/java-tests/testData/codeInsight/generateConstructor/beforeNoMoreConstructorsCanBeGenerated.java

@@ -0,0 +1,6 @@
+public class Test {
+  <caret>
+
+  public Test() {
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/GenerateConstructorTest.java

@@ -17,6 +17,7 @@ public class GenerateConstructorTest extends LightCodeInsightTestCase {
   public void testBoundComments() throws Exception { doTest(); }
   public void testSameNamedFields() throws Exception { doTest(); }
   public void testEnumWithAbstractMethod() throws Exception { doTest(); }
+  public void testNoMoreConstructorsCanBeGenerated() throws Exception { doTest(); }
 
   public void testImmediatelyAfterRBrace() throws Exception {    // IDEADEV-28811
     final CodeStyleSettings settings = CodeStyleSettingsManager.getInstance(getProject()).getCurrentSettings();