unused constructor parameters have quickfix to initialize field (PY-1398)

python/src/com/jetbrains/python/actions/AddFieldQuickFix.java

@@ -25,11 +25,13 @@ import org.jetbrains.annotations.Nullable;
 public class AddFieldQuickFix implements LocalQuickFix {
 
   private PyClass myQualifierClass;
+  private final String myInitializer;
   private String myIdentifier;
 
-  public AddFieldQuickFix(String identifier, PyClass qualifierClass) {
+  public AddFieldQuickFix(String identifier, PyClass qualifierClass, String initializer) {
     myIdentifier = identifier;
     myQualifierClass = qualifierClass;
+    myInitializer = initializer;
   }
 
   @NotNull
@@ -67,7 +69,7 @@ public class AddFieldQuickFix implements LocalQuickFix {
     PyClass cls = myQualifierClass;
     String item_name = myIdentifier;
     if (cls != null) {
-      PsiElement initStatement = addFieldToInit(project, cls, item_name, new CreateFieldCallback(project, item_name));
+      PsiElement initStatement = addFieldToInit(project, cls, item_name, new CreateFieldCallback(project, item_name, myInitializer));
       if (initStatement != null) {
         showTemplateBuilder(initStatement);
         return;
@@ -77,11 +79,11 @@ public class AddFieldQuickFix implements LocalQuickFix {
     PyUtil.showBalloon(project, PyBundle.message("QFIX.failed.to.add.field"), MessageType.ERROR);
   }
 
-  private static void showTemplateBuilder(PsiElement initStatement) {
+  private void showTemplateBuilder(PsiElement initStatement) {
     initStatement = CodeInsightUtilBase.forcePsiPostprocessAndRestoreElement(initStatement);
     if (initStatement instanceof PyAssignmentStatement) {
       final TemplateBuilder builder = TemplateBuilderFactory.getInstance().createTemplateBuilder(initStatement);
-      builder.replaceElement(((PyAssignmentStatement) initStatement).getAssignedValue(), "None");
+      builder.replaceElement(((PyAssignmentStatement) initStatement).getAssignedValue(), myInitializer);
       builder.run();
     }
   }
@@ -159,14 +161,16 @@ public class AddFieldQuickFix implements LocalQuickFix {
   private static class CreateFieldCallback implements Function<String, PyStatement> {
     private Project myProject;
     private String myItemName;
+    private String myInitializer;
 
-    private CreateFieldCallback(Project project, String itemName) {
+    private CreateFieldCallback(Project project, String itemName, String initializer) {
       myProject = project;
       myItemName = itemName;
+      myInitializer = initializer;
     }
 
     public PyStatement fun(String self_name) {
-      return PyElementGenerator.getInstance(myProject).createFromText(PyStatement.class, self_name + "." + myItemName + " = None");
+      return PyElementGenerator.getInstance(myProject).createFromText(PyStatement.class, self_name + "." + myItemName + " = " + myInitializer);
     }
   }
 }

python/src/com/jetbrains/python/inspections/PyUnresolvedReferencesInspection.java

@@ -210,7 +210,7 @@ public class PyUnresolvedReferencesInspection extends PyInspection {
                     if (reference.getElement().getParent() instanceof PyCallExpression) {
                       actions.add(new AddMethodQuickFix(ref_text, (PyClassType)qtype));
                     }
-                    else actions.add(new AddFieldQuickFix(ref_text, cls));
+                    else actions.add(new AddFieldQuickFix(ref_text, cls, "None"));
                   }
                 }
                 description_buf.append(PyBundle.message("INSP.unresolved.ref.$0.for.class.$1", ref_text, qtype.getName()));

python/src/com/jetbrains/python/inspections/PyUnusedLocalInspectionVisitor.java

@@ -17,6 +17,8 @@ import com.intellij.psi.ResolveResult;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.Function;
 import com.jetbrains.python.PyBundle;
+import com.jetbrains.python.PyNames;
+import com.jetbrains.python.actions.AddFieldQuickFix;
 import com.jetbrains.python.codeInsight.controlflow.ReadWriteInstruction;
 import com.jetbrains.python.codeInsight.controlflow.ScopeOwner;
 import com.jetbrains.python.codeInsight.dataflow.scope.Scope;
@@ -244,14 +246,23 @@ class PyUnusedLocalInspectionVisitor extends PyInspectionVisitor {
               continue;
             }
           }
+          boolean isInitMethod = false;
+          PyClass containingClass = null;
           PyParameterList paramList = PsiTreeUtil.getParentOfType(element, PyParameterList.class);
           if (paramList != null && paramList.getParent() instanceof PyFunction) {
             PyFunction func = (PyFunction) paramList.getParent();
-            if (canHaveUnusedParameters(func, functionsWithInheritors)) {
+            containingClass = func.getContainingClass();
+            if (PyNames.INIT.equals(func.getName()) && containingClass != null) {
+              isInitMethod = true;
+            }
+            else if (ignoreUnusedParameters(func, functionsWithInheritors)) {
               continue;
             }
           }
-          registerWarning(element, PyBundle.message("INSP.unused.locals.parameter.isnot.used", name));
+          LocalQuickFix[] fixes = isInitMethod
+                                  ? new LocalQuickFix[] { new AddFieldQuickFix(name, containingClass, name) }
+                                  : LocalQuickFix.EMPTY_ARRAY;
+          registerWarning(element, PyBundle.message("INSP.unused.locals.parameter.isnot.used", name), fixes);
         }
         else {
           if (myIgnoreTupleUnpacking && isTupleUnpacking(element)) {
@@ -269,7 +280,7 @@ class PyUnusedLocalInspectionVisitor extends PyInspectionVisitor {
     }
   }
 
-  private static boolean canHaveUnusedParameters(PyFunction func, Set<PyFunction> functionsWithInheritors) {
+  private static boolean ignoreUnusedParameters(PyFunction func, Set<PyFunction> functionsWithInheritors) {
     if (functionsWithInheritors.contains(func)) {
       return true;
     }
@@ -297,8 +308,8 @@ class PyUnusedLocalInspectionVisitor extends PyInspectionVisitor {
     return false;
   }
 
-  private void registerWarning(final PsiElement element, final String msg) {
-    registerProblem(element, msg, ProblemHighlightType.LIKE_UNUSED_SYMBOL, null);
+  private void registerWarning(final PsiElement element, final String msg, LocalQuickFix... quickfixes) {
+    registerProblem(element, msg, ProblemHighlightType.LIKE_UNUSED_SYMBOL, null, quickfixes);
   }
 
   private static class ReplaceWithWildCard implements LocalQuickFix {

python/testData/inspections/FieldFromUnusedParameter.py

@@ -0,0 +1,3 @@
+class A:
+    def __init__(self, <warning descr="Parameter 'foo' value is not used">f<caret>oo</warning>):
+        pass

python/testData/inspections/FieldFromUnusedParameter_after.py

@@ -0,0 +1,3 @@
+class A:
+    def __init__(self, foo):
+        self.foo = foo

python/testSrc/com/jetbrains/python/PyQuickFixTest.java

@@ -144,6 +144,10 @@ public class PyQuickFixTest extends PyLightFixtureTestCase {
     doInspectionTest("AddClass.py", PyUnresolvedReferencesInspection.class, "Create class 'Xyzzy'", true, true);
   }
 
+  public void testFieldFromUnusedParameter() {  // PY-1398
+    doInspectionTest("FieldFromUnusedParameter.py", PyUnusedLocalInspection.class, "Add field 'foo' to class A", true, true);
+  }
+
   @NonNls
   protected String getTestDataPath() {
     return PythonTestUtil.getTestDataPath() + "/inspections/";