PY-18522 PY-19053 Paste raw text if there are non whitespace symbols before caret on line

This previously existed check was lost after the recent fixes for
PY-18522. It also caused failures of PyCopyPasteTest.testEmpty(), so
I reverted previous fix for the test.

python/src/com/jetbrains/python/editor/PythonCopyPasteProcessor.java

@@ -82,6 +82,9 @@ public class PythonCopyPasteProcessor implements CopyPastePreProcessor {
     final int lineStartOffset = getLineStartSafeOffset(document, lineNumber);
     final int lineEndOffset = document.getLineEndOffset(lineNumber);
 
+    final String linePrefix = document.getText(TextRange.create(lineStartOffset, caretOffset));
+    if (!StringUtil.isEmptyOrSpaces(linePrefix)) return text;
+    
     final PsiElement element = file.findElementAt(caretOffset);
     if (PsiTreeUtil.getParentOfType(element, PyStringLiteralExpression.class) != null) return text;
 
@@ -186,15 +189,13 @@ public class PythonCopyPasteProcessor implements CopyPastePreProcessor {
   }
 
   private static boolean isApplicable(@NotNull final PsiFile file, @NotNull String text, int caretOffset) {
-    final boolean useTabs = CodeStyleSettingsManager.getSettings(file.getProject()).useTabCharacter(PythonFileType.INSTANCE);
+    final boolean useTabs =
+      CodeStyleSettingsManager.getSettings(file.getProject()).useTabCharacter(PythonFileType.INSTANCE);
     final PsiElement nonWS = PyUtil.findNextAtOffset(file, caretOffset, PsiWhiteSpace.class);
-    if (nonWS == null) {
-      return !StringUtil.isEmptyOrSpaces(text);
-    }
-    if (text.endsWith("\n") ||
-        (inStatementList(file, caretOffset) && (text.startsWith(useTabs ? "\t" : " ") || StringUtil.split(text, "\n").size() > 1))) {
+    if (nonWS == null || text.endsWith("\n"))
+      return true;
+    if (inStatementList(file, caretOffset) && (text.startsWith(useTabs ? "\t" : " ") || StringUtil.split(text, "\n").size() > 1))
       return true;
-    }
     return false;
   }
 

python/testData/copyPaste/SimpleExpressionPartCaretAtLineEnd.after.py

@@ -0,0 +1,2 @@
+def foo():
+    x = 10 * 20

python/testData/copyPaste/SimpleExpressionPartCaretAtLineEnd.dst.py

@@ -0,0 +1,2 @@
+def foo():
+    x = 10 * <caret>

python/testData/copyPaste/SimpleExpressionPartCaretAtLineEnd.src.py

@@ -0,0 +1 @@
+<selection>20</selection>

python/testSrc/com/jetbrains/python/PyCopyPasteTest.java

@@ -391,4 +391,9 @@ public class PyCopyPasteTest extends PyTestCase {
   public void testEmptyFunctionCaretAtBodyIndent() {
     doTest();
   }
+
+  // PY-19053
+  public void testSimpleExpressionPartCaretAtLineEnd() {
+    doTest();
+  }
 }