optimize imports inserts blank lines between groups also when we don't have any missorted imports (PY-8355)

python/src/com/jetbrains/python/codeInsight/imports/PyImportOptimizer.java

@@ -107,11 +107,19 @@ public class PyImportOptimizer implements ImportOptimizer {
           prioritize(importStatement, toImport);
         }
       }
-      if (myMissorted) {
+      if (myMissorted || needBlankLinesBetweenGroups()) {
         applyResults();
       }
     }
 
+    private boolean needBlankLinesBetweenGroups() {
+      int nonEmptyGroups = 0;
+      if (myBuiltinImports.size() > 0) nonEmptyGroups++;
+      if (myThirdPartyImports.size() > 0) nonEmptyGroups++;
+      if (myProjectImports.size() > 0) nonEmptyGroups++;
+      return nonEmptyGroups > 1;
+    }
+
     private void prioritize(PyImportStatementBase importStatement, @Nullable PsiElement toImport) {
       if (toImport != null && !(toImport instanceof PsiFileSystemItem)) {
         toImport = toImport.getContainingFile();
@@ -143,7 +151,10 @@ public class PyImportOptimizer implements ImportOptimizer {
       addImports(myThirdPartyImports);
       addImports(myProjectImports);
       PsiElement lastElement = myImportBlock.get(myImportBlock.size()-1);
-      myFile.deleteChildRange(findFirstNonFutureImport(), lastElement);
+      PyImportStatementBase firstNonFutureImport = findFirstNonFutureImport();
+      if (firstNonFutureImport != null) {
+        myFile.deleteChildRange(firstNonFutureImport, lastElement);
+      }
       for (PyImportStatementBase anImport : myBuiltinImports) {
         anImport.putCopyableUserData(PyBlock.IMPORT_GROUP_BEGIN, null);
       }
@@ -155,7 +166,7 @@ public class PyImportOptimizer implements ImportOptimizer {
           return importStatement;
         }
       }
-      return myImportBlock.get(0);
+      return null;
     }
 
     private static void markGroupBegin(List<PyImportStatementBase> imports) {

python/testData/optimizeImports/insertBlankLines.after.py

@@ -0,0 +1,10 @@
+from __future__ import with_statement
+import sys
+import datetime
+
+import foo
+from bar import *
+
+
+sys.path
+datetime.datetime

python/testData/optimizeImports/insertBlankLines.py

@@ -0,0 +1,9 @@
+from __future__ import with_statement
+import sys
+import datetime
+import foo
+from bar import *
+
+
+sys.path
+datetime.datetime

python/testSrc/com/jetbrains/python/PyOptimizeImportsTest.java

@@ -63,6 +63,10 @@ public class PyOptimizeImportsTest extends PyTestCase {
     doTest();
   }
 
+  public void testInsertBlankLines() {  // PY-8355
+    doTest();
+  }
+
   private void doTest() {
     myFixture.configureByFile("optimizeImports/" + getTestName(true) + ".py");
     OptimizeImportsAction.actionPerformedImpl(DataManager.getInstance().getDataContext(myFixture.getEditor().getContentComponent()));