PY-15653 Smart enter works better in case of function and class definitions without name element

python/src/com/jetbrains/python/codeInsight/editorActions/smartEnter/fixers/PyFunctionFixer.java

@@ -15,7 +15,6 @@
  */
 package com.jetbrains.python.codeInsight.editorActions.smartEnter.fixers;
 
-import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.Editor;
 import com.intellij.psi.PsiElement;
 import com.intellij.util.IncorrectOperationException;
@@ -43,12 +42,21 @@ public class PyFunctionFixer extends PyFixer<PyFunction> {
     final PsiElement colon = PyUtil.getFirstChildOfType(function, PyTokenTypes.COLON);
     if (!isFakeFunction(function) && colon == null) {
       final PyParameterList parameterList = function.getParameterList();
-      final Document document = editor.getDocument();
-      document.insertString(parameterList.getTextRange().getEndOffset(), ":");
+      if (function.getNameNode() == null) {
+        processor.registerUnresolvedError(parameterList.getTextOffset());
+      }
+      editor.getDocument().insertString(parameterList.getTextRange().getEndOffset(), ":");
     }
   }
 
-  private static boolean isFakeFunction(PyFunction function) {
+  /**
+   * Python parser can create empty function element without header and body solely to enclose {@link com.jetbrains.python.psi.PyDecoratorList}.
+   * Attempting to operate in the context of such "fake" function definition may lead to various kinds of malformed code and we want to
+   * avoid it.
+   *
+   * @return whether it's more the less proper function definition, i.e. it contains at least {@code def} keyword
+   */
+  static boolean isFakeFunction(@NotNull PyFunction function) {
     return function.getNode().findChildByType(PyTokenTypes.DEF_KEYWORD) == null;
   }
 }

python/src/com/jetbrains/python/codeInsight/editorActions/smartEnter/fixers/PyParameterListFixer.java

@@ -40,22 +40,20 @@ public class PyParameterListFixer extends PyFixer<PyParameterList> {
   }
 
   @Override
-  public void doApply(@NotNull Editor editor, @NotNull PySmartEnterProcessor processor, @NotNull PyParameterList psiElement) throws IncorrectOperationException {
+  public void doApply(@NotNull Editor editor, @NotNull PySmartEnterProcessor processor, @NotNull PyParameterList psiElement)
+    throws IncorrectOperationException {
     final PsiElement lBrace = PyUtil.getChildByFilter(psiElement, PyTokenTypes.OPEN_BRACES, 0);
     final PsiElement rBrace = PyUtil.getChildByFilter(psiElement, PyTokenTypes.CLOSE_BRACES, 0);
-    if (!isFakeParameterList(psiElement) && (lBrace == null || rBrace == null)) {
+    final PyFunction pyFunction = as(psiElement.getParent(), PyFunction.class);
+    if (pyFunction != null && !PyFunctionFixer.isFakeFunction(pyFunction) && (lBrace == null || rBrace == null)) {
       final Document document = editor.getDocument();
       if (lBrace == null) {
-        document.insertString(psiElement.getTextRange().getStartOffset(), "(");
+        final String textToInsert = pyFunction.getNameNode() == null ? " (" : "(";
+        document.insertString(psiElement.getTextOffset(), textToInsert);
       }
       else {
         document.insertString(psiElement.getTextRange().getEndOffset(), ")");
       }
     }
   }
-
-  private static boolean isFakeParameterList(@NotNull PyParameterList parameterList) {
-    final PyFunction pyFunction = as(parameterList.getParent(), PyFunction.class);
-    return pyFunction != null && pyFunction.getNode().findChildByType(PyTokenTypes.DEF_KEYWORD) == null;
-  }
 }

python/testData/codeInsight/smartEnter/classKeywordOnly.py

@@ -0,0 +1 @@
+class<caret>

python/testData/codeInsight/smartEnter/classKeywordOnly_after.py

@@ -0,0 +1 @@
+class <caret>:

python/testData/codeInsight/smartEnter/defKeywordOnly.py

@@ -0,0 +1 @@
+def<caret>

python/testData/codeInsight/smartEnter/defKeywordOnly_after.py

@@ -0,0 +1 @@
+def <caret>():

python/testSrc/com/jetbrains/python/PySmartEnterTest.java

@@ -170,6 +170,16 @@ public class PySmartEnterTest extends PyTestCase {
     }
   }
 
+  // PY-15653
+  public void testClassKeywordOnly() {
+    doTest();
+  }
+
+  // PY-15653
+  public void testDefKeywordOnly() {
+    doTest();
+  }
+
   // PY-12877
   public void testWithTargetOmitted() {
     doTest();