IDEA-201703 Allow extract variable from field initializer

java/java-impl/src/com/intellij/refactoring/introduceVariable/IntroduceVariableBase.java

@@ -62,6 +62,7 @@ import com.intellij.util.IncorrectOperationException;
 import com.intellij.util.Processor;
 import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.containers.MultiMap;
+import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -162,7 +163,9 @@ public abstract class IntroduceVariableBase extends IntroduceHandlerBase {
 
       if (!selectionModel.hasSelection()) {
         final List<PsiExpression> expressions = ContainerUtil
-          .filter(collectExpressions(file, editor, offset), expression -> RefactoringUtil.getParentStatement(expression, false) != null);
+          .filter(collectExpressions(file, editor, offset), expression -> 
+            RefactoringUtil.getParentStatement(expression, false) != null ||
+            PsiTreeUtil.getParentOfType(expression, PsiField.class, true, PsiStatement.class) != null);
         if (expressions.isEmpty()) {
           selectionModel.selectLineAtCaret();
         } else if (!isChooserNeeded(expressions)) {
@@ -612,7 +615,7 @@ public abstract class IntroduceVariableBase extends IntroduceHandlerBase {
 
     final PsiElement physicalElement = expr.getUserData(ElementToWorkOn.PARENT);
 
-    final PsiElement anchorStatement = RefactoringUtil.getParentStatement(physicalElement != null ? physicalElement : expr, false);
+    final PsiElement anchorStatement = getAnchor(physicalElement != null ? physicalElement : expr);
 
     PsiElement tempContainer = checkAnchorStatement(project, editor, anchorStatement);
     if (tempContainer == null) return false;
@@ -756,6 +759,19 @@ public abstract class IntroduceVariableBase extends IntroduceHandlerBase {
     return wasSucceed[0];
   }
 
+  @Nullable
+  private static PsiElement getAnchor(PsiElement place) {
+    PsiElement anchorStatement = RefactoringUtil.getParentStatement(place, false);
+    if (anchorStatement == null) {
+      PsiField field = PsiTreeUtil.getParentOfType(place, PsiField.class, true, PsiStatement.class);
+      if (field != null) {
+        anchorStatement = field.getInitializer();
+      }
+    }
+    return anchorStatement;
+  }
+
+  @Contract("_, _, null -> null")
   protected PsiElement checkAnchorStatement(Project project, Editor editor, PsiElement anchorStatement) {
     if (anchorStatement == null) {
       String message = RefactoringBundle.message("refactoring.is.not.supported.in.the.current.context", REFACTORING_NAME);

java/java-impl/src/com/intellij/refactoring/util/occurrences/BaseOccurrenceManager.java

@@ -78,7 +78,8 @@ public abstract class BaseOccurrenceManager implements OccurrenceManager {
   }
   @Override
   public PsiElement getAnchorStatementForAllInScope(PsiElement scope) {
-    return RefactoringUtil.getAnchorElementForMultipleExpressions(myOccurrences, scope);
+    PsiElement anchor = RefactoringUtil.getAnchorElementForMultipleExpressions(myOccurrences, scope);
+    return anchor instanceof PsiField ? ((PsiField)anchor).getInitializer() : anchor;
   }
 
   private static boolean needToDeclareFinal(PsiExpression[] occurrences) {

java/java-tests/testData/refactoring/introduceVariable/Field.after.java

@@ -0,0 +1,8 @@
+class Test {
+    private static final String STRING;
+
+    static {
+        String temp = "foo".trim();
+        STRING = temp +"foo".trim();
+    }
+}

java/java-tests/testData/refactoring/introduceVariable/Field.java

@@ -0,0 +1,3 @@
+class Test {
+    private static final String STRING = <selection>"foo".trim()</selection>+"foo".trim();
+}

java/java-tests/testData/refactoring/introduceVariable/FieldAll.after.java

@@ -0,0 +1,8 @@
+class Test {
+    private static final String STRING;
+
+    static {
+        String temp = "foo".trim();
+        STRING = temp + temp;
+    }
+}

java/java-tests/testData/refactoring/introduceVariable/FieldAll.java

@@ -0,0 +1,3 @@
+class Test {
+    private static final String STRING = <selection>"foo".trim()</selection>+"foo".trim();
+}

java/java-tests/testSrc/com/intellij/java/refactoring/IntroduceVariableTest.java

@@ -203,6 +203,14 @@ public class IntroduceVariableTest extends LightCodeInsightTestCase {
   public void testWhileCondition2() {
     doTest(new MockIntroduceVariableHandler("temp", true, false, false, "Node"));
   }
+  
+  public void testField() {
+    doTest(new MockIntroduceVariableHandler("temp", false, false, false, CommonClassNames.JAVA_LANG_STRING));
+  }
+  
+  public void testFieldAll() {
+    doTest(new MockIntroduceVariableHandler("temp", true, false, false, CommonClassNames.JAVA_LANG_STRING));
+  }
 
   public void testCaseLabel() {
     doTest(new MockIntroduceVariableHandler("temp", true, false, false, "int"));