do not use the same formatting rules inside string literals

fixed PY-9661 Fill paragraph generally bad

python/src/com/jetbrains/python/formatter/PyLineWrapPositionStrategy.java

@@ -2,9 +2,16 @@ package com.jetbrains.python.formatter;
 
 import com.intellij.openapi.editor.Document;
 import com.intellij.openapi.editor.GenericLineWrapPositionStrategy;
+import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.text.StringUtil;
+import com.intellij.psi.PsiDocumentManager;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiFile;
+import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.text.CharArrayUtil;
+import com.jetbrains.python.psi.StringLiteralExpression;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * @author yole
@@ -44,4 +51,37 @@ public class PyLineWrapPositionStrategy extends GenericLineWrapPositionStrategy
     }
     return text.charAt(i - 2) != 'd' || text.charAt(i - 1) != 'e' || text.charAt(i) != 'f';
   }
+
+  @Override
+  public int calculateWrapPosition(@NotNull Document document,
+                                   @Nullable Project project,
+                                   int startOffset,
+                                   int endOffset,
+                                   int maxPreferredOffset,
+                                   boolean allowToBeyondMaxPreferredOffset,
+                                   boolean virtual) {
+    int wrapPosition =
+      super.calculateWrapPosition(document, project, startOffset, endOffset, maxPreferredOffset, allowToBeyondMaxPreferredOffset, virtual);
+    if (wrapPosition < 0) return wrapPosition;
+    final CharSequence text = document.getCharsSequence();
+
+    char c = text.charAt(wrapPosition);
+    if (!StringUtil.isWhiteSpace(c) || project == null) {
+      return wrapPosition;
+    }
+
+    final PsiDocumentManager documentManager = PsiDocumentManager.getInstance(project);
+    if (documentManager != null) {
+      final PsiFile psiFile = documentManager.getPsiFile(document);
+      if (psiFile != null) {
+        final PsiElement element = psiFile.findElementAt(wrapPosition);
+        final StringLiteralExpression string = PsiTreeUtil.getParentOfType(element, StringLiteralExpression.class);
+
+        if (string != null) {
+          return wrapPosition + 1;
+        }
+      }
+    }
+    return wrapPosition;
+  }
 }

python/testData/fillParagraph/multilineDocstring_after.py

@@ -3,6 +3,6 @@ __author__ = 'ktisha'
 def foo():
     """
     This is my docstring. There are many like it, but this one mine. My docstring is my best friend. it is my life. I
-     must master it as I must master my life. This is my docstring. There are many like it, but this one mine. My
-     docstring is my best friend. it is my life. I must master it as I must master my life.
+    must master it as I must master my life. This is my docstring. There are many like it, but this one mine. My
+    docstring is my best friend. it is my life. I must master it as I must master my life.
     """

python/testData/fillParagraph/singleLine_after.py

@@ -1,4 +1,4 @@
 def f():
   """ This is my docstring. There are many like it, but this one mine. My docstring is my best friend. it is my life.
-   I must master it as I must master my life.
+  I must master it as I must master my life.
   """