bpo-38862: IDLE Strip Trailing Whitespace fixes end newlines (GH-17366)

Extra newlines are removed at the end of non-shell files. If the file only has newlines after stripping other trailing whitespace, all are removed, as is done by patchcheck.py.

1 files changed, 10 insertions, 0 deletions

diff --git a/Lib/idlelib/format.py b/Lib/idlelib/format.py
index 2b09805657..4b57a182c9 100644
--- a/Lib/idlelib/format.py
+++ b/Lib/idlelib/format.py
@@ -408,6 +408,16 @@ class Rstrip:  # 'Strip Trailing Whitespace" on "Format" menu.
             if cut < raw:
                 text.delete('%i.%i' % (cur, cut), '%i.end' % cur)
 
+        if (text.get('end-2c') == '\n'  # File ends with at least 1 newline;
+            and not hasattr(self.editwin, 'interp')):  # & is not Shell.
+            # Delete extra user endlines.
+            while (text.index('end-1c') > '1.0'  # Stop if file empty.
+                   and text.get('end-3c') == '\n'):
+                text.delete('end-3c')
+            # Because tk indexes are slice indexes and never raise,
+            # a file with only newlines will be emptied.
+            # patchcheck.py does the same.
+
         undo.undo_block_stop()