avoid inserting duplicate colon when adding 'self' (PY-2652)

python/src/com/jetbrains/python/codeInsight/PyMethodNameTypedHandler.java

@@ -14,7 +14,6 @@ import com.jetbrains.python.PyNames;
 import com.jetbrains.python.PyTokenTypes;
 import com.jetbrains.python.PythonFileType;
 import com.jetbrains.python.psi.PyFunction;
-import com.jetbrains.python.psi.PyStringLiteralExpression;
 import com.jetbrains.python.psi.PyUtil;
 
 /**
@@ -55,7 +54,13 @@ public class PyMethodNameTypedHandler extends TypedHandlerDelegate {
                 else if (flags.isStaticMethod()) pname="";
                 documentManager.commitDocument(document);
                 // TODO: only print the ")" if Settings require it
-                EditorModificationUtil.typeInStringAtCaretHonorBlockSelection(editor, "("+pname+"):", true);
+                int caretOffset = editor.getCaretModel().getOffset();
+                String textToType = "(" + pname + ")";
+                CharSequence chars = editor.getDocument().getCharsSequence();
+                if (caretOffset == chars.length() || chars.charAt(caretOffset) != ':') {
+                  textToType += ':';
+                }
+                EditorModificationUtil.typeInStringAtCaretHonorBlockSelection(editor, textToType, true);
                 editor.getCaretModel().moveToOffset(offset + 1 + pname.length()); // right after param name
                 return Result.STOP;
               }

python/testData/editing/firstParamDuplicateColon.after.py

@@ -0,0 +1,2 @@
+class C:
+    def someDefName(self):

python/testData/editing/firstParamDuplicateColon.py

@@ -0,0 +1,2 @@
+class C:
+    def someDefName<caret>:

python/testSrc/com/jetbrains/python/PyEditingTest.java

@@ -233,4 +233,8 @@ public class PyEditingTest extends PyLightFixtureTestCase {
   public void testFirstParamStaticmethod() {
     doTypingTest('(');
   }
+
+  public void testFirstParamDuplicateColon() {  // PY-2652
+    doTypingTest('(');
+  }
 }