java call completion: remove untouched argument placeholders when template is broken off

java/java-impl/src/com/intellij/codeInsight/completion/JavaMethodCallElement.java

@@ -21,11 +21,14 @@ import com.intellij.codeInsight.lookup.*;
 import com.intellij.codeInsight.lookup.impl.JavaElementLookupRenderer;
 import com.intellij.codeInsight.template.*;
 import com.intellij.codeInsight.template.impl.ConstantNode;
+import com.intellij.codeInsight.template.impl.TemplateImpl;
 import com.intellij.codeInsight.template.impl.TemplateManagerImpl;
 import com.intellij.codeInsight.template.impl.TemplateState;
 import com.intellij.featureStatistics.FeatureUsageTracker;
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.editor.event.DocumentAdapter;
+import com.intellij.openapi.editor.event.DocumentEvent;
 import com.intellij.openapi.util.ClassConditionKey;
 import com.intellij.openapi.util.Disposer;
 import com.intellij.openapi.util.Key;
@@ -40,6 +43,8 @@ import com.intellij.psi.util.TypeConversionUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.concurrent.atomic.AtomicInteger;
+
 /**
  * @author peter
  */
@@ -243,6 +248,8 @@ public class JavaMethodCallElement extends LookupItem<PsiMethod> implements Type
     TemplateState templateState = TemplateManagerImpl.getTemplateState(editor);
     if (templateState == null) return;
 
+    setupNonFilledArgumentRemoving(editor, templateState);
+
     editor.putUserData(ARGUMENT_TEMPLATE_ACTIVE, this);
     Disposer.register(templateState, () -> {
       if (editor.getUserData(ARGUMENT_TEMPLATE_ACTIVE) == this) {
@@ -251,6 +258,41 @@ public class JavaMethodCallElement extends LookupItem<PsiMethod> implements Type
     });
   }
 
+  private static void setupNonFilledArgumentRemoving(final Editor editor, final TemplateState templateState) {
+    AtomicInteger maxEditedVariable = new AtomicInteger(-1);
+    editor.getDocument().addDocumentListener(new DocumentAdapter() {
+      @Override
+      public void documentChanged(DocumentEvent e) {
+        maxEditedVariable.set(Math.max(maxEditedVariable.get(), templateState.getCurrentVariableNumber()));
+      }
+    }, templateState);
+
+    templateState.addTemplateStateListener(new TemplateEditingAdapter() {
+      @Override
+      public void currentVariableChanged(TemplateState templateState, Template template, int oldIndex, int newIndex) {
+        maxEditedVariable.set(Math.max(maxEditedVariable.get(), oldIndex));
+      }
+
+      @Override
+      public void beforeTemplateFinished(TemplateState state, Template template, boolean brokenOff) {
+        if (brokenOff) {
+          removeUntouchedArguments((TemplateImpl)template);
+        }
+      }
+
+      private void removeUntouchedArguments(TemplateImpl template) {
+        int firstUnchangedVar = maxEditedVariable.get() + 1;
+        if (firstUnchangedVar >= template.getVariableCount()) return;
+
+        TextRange startRange = templateState.getVariableRange(template.getVariableNameAt(firstUnchangedVar));
+        TextRange endRange = templateState.getVariableRange(template.getVariableNameAt(template.getVariableCount() - 1));
+        if (startRange == null || endRange == null) return;
+
+        editor.getDocument().deleteString(startRange.getStartOffset(), endRange.getEndOffset());
+      }
+    });
+  }
+
   private boolean shouldInsertTypeParameters() {
     return myMayNeedExplicitTypeParameters && !getInferenceSubstitutor().equals(PsiSubstitutor.EMPTY) && myMethod.getParameterList().getParametersCount() == 0;
   }

platform/lang-impl/src/com/intellij/codeInsight/template/TemplateEditingListener.java

@@ -23,6 +23,11 @@ import com.intellij.codeInsight.template.impl.TemplateState;
  */
 public interface TemplateEditingListener {
   void beforeTemplateFinished(TemplateState state, Template template);
+
+  default void beforeTemplateFinished(TemplateState state, Template template, boolean brokenOff) {
+    beforeTemplateFinished(state, template);
+  }
+
   void templateFinished(Template template, boolean brokenOff);
   void templateCancelled(Template template);
   void currentVariableChanged(TemplateState templateState, Template template, int oldIndex, int newIndex);

platform/lang-impl/src/com/intellij/codeInsight/template/impl/TemplateState.java

@@ -1090,7 +1090,7 @@ public class TemplateState implements Disposable {
 
   private void cleanupTemplateState(boolean brokenOff) {
     final Editor editor = myEditor;
-    fireBeforeTemplateFinished();
+    fireBeforeTemplateFinished(brokenOff);
     if (!isDisposed()) {
       int oldVar = myCurrentVariableNumber;
       setCurrentVariableNumber(-1);
@@ -1398,9 +1398,9 @@ public class TemplateState implements Disposable {
     }
   }
 
-  private void fireBeforeTemplateFinished() {
+  private void fireBeforeTemplateFinished(boolean brokenOff) {
     for (TemplateEditingListener listener : myListeners) {
-      listener.beforeTemplateFinished(this, myTemplate);
+      listener.beforeTemplateFinished(this, myTemplate, brokenOff);
     }
   }