Add RemoveTrailingWhitespaceVisitor (#100)

* Add RemoveTrailingWhitespaceVisitor

* Add pre/post visit methods

* Fix attribute

* Call RemoveTrailingWhiteSpaceVisitor in AutoFormatVisitor

* Update rewrite/rewrite/python/format/remove_trailing_whitespace_visitor.py

Co-authored-by: Knut Wannheden <[email protected]>

* Fix for trailing comma and clean

---------

Co-authored-by: Knut Wannheden <[email protected]>

rewrite/rewrite/python/format/auto_format.py

@@ -2,6 +2,7 @@
 
 from .blank_lines import BlankLinesVisitor
 from .normalize_format import NormalizeFormatVisitor
+from .remove_trailing_whitespace_visitor import RemoveTrailingWhitespaceVisitor
 from .spaces_visitor import SpacesVisitor
 from .normalize_tabs_or_spaces import NormalizeTabsOrSpacesVisitor
 from .. import TabsAndIndentsStyle
@@ -32,4 +33,5 @@ def visit(self, tree: Optional[Tree], p: P, parent: Optional[Cursor] = None) ->
             cu.get_style(TabsAndIndentsStyle) or IntelliJ.tabs_and_indents(),
             self._stop_after
         ).visit(tree, p, self._cursor.fork())
+        tree = RemoveTrailingWhitespaceVisitor(self._stop_after).visit(tree, self._cursor.fork())
         return tree

rewrite/rewrite/python/format/remove_trailing_whitespace_visitor.py

@@ -0,0 +1,54 @@
+from typing import Optional, cast, Union
+
+import rewrite.java as j
+import rewrite.python as p
+from rewrite import Tree, Marker
+from rewrite.java import Space, J, TrailingComma
+from rewrite.python import PythonVisitor, CompilationUnit, PySpace
+from rewrite.visitor import P, Cursor, T
+
+
+class RemoveTrailingWhitespaceVisitor(PythonVisitor):
+    def __init__(self, stop_after: Optional[p.Tree] = None):
+        self._stop_after = stop_after
+        self._stop = False
+
+    def visit_compilation_unit(self, compilation_unit: CompilationUnit, p: P) -> J:
+        if not compilation_unit.prefix.comments:
+            compilation_unit = compilation_unit.with_prefix(Space.EMPTY)
+        cu: j.CompilationUnit = cast(j.CompilationUnit, super().visit_compilation_unit(compilation_unit, p))
+
+        if cu.eof.whitespace:
+            clean = "".join([_ for _ in cu.eof.whitespace if _ in ['\n', '\r']])
+            cu = cu.with_eof(cu.eof.with_whitespace(clean))
+
+        return cu
+
+    def visit_space(self, space: Optional[Space], loc: Optional[Union[PySpace.Location, Space.Location]],
+                    p: P) -> Space:
+        s = cast(Space, super().visit_space(space, loc, p))
+        if not s or not s.whitespace:
+            return s
+        return self._normalize_whitespace(s)
+
+    def visit_marker(self, marker: Marker, p: P) -> Marker:
+        m = cast(Marker, super().visit_marker(marker, p))
+        if isinstance(m, TrailingComma):
+            return m.with_suffix(self._normalize_whitespace(m.suffix))
+        return m
+
+    @staticmethod
+    def _normalize_whitespace(s):
+        last_newline = s.whitespace.rfind('\n')
+        if last_newline > 0:
+            ws = [c for i, c in enumerate(s.whitespace) if i >= last_newline or c in {'\r', '\n'}]
+            s = s.with_whitespace(''.join(ws))
+        return s
+
+    def post_visit(self, tree: T, p: P) -> Optional[T]:
+        if self._stop_after and tree == self._stop_after:
+            self._stop = True
+        return tree
+
+    def visit(self, tree: Optional[Tree], p: P, parent: Optional[Cursor] = None) -> Optional[T]:
+        return tree if self._stop else super().visit(tree, p, parent)

rewrite/tests/python/all/format/remove_trailing_whitespace_visitor_test.py

@@ -0,0 +1,68 @@
+import pytest
+
+from rewrite.python.format.remove_trailing_whitespace_visitor import RemoveTrailingWhitespaceVisitor
+from rewrite.test import rewrite_run, RecipeSpec, from_visitor, python
+
+
+@pytest.mark.parametrize('n_spaces', list(range(0, 4)))
+@pytest.mark.parametrize('linebreaks', ['\n', '\r\n', '\r\n\n', '\n\n'])
+def test_tabs_to_spaces(n_spaces, linebreaks):
+    # noinspection PyInconsistentIndentation
+    spaces = ' ' * n_spaces
+    rewrite_run(
+        python(
+            # language=python
+            f"""\
+            class Foo:{spaces}{linebreaks}\
+                def bar(self):
+                    return 42{linebreaks}
+            {spaces}{linebreaks}
+            """,
+            # language=python
+            f"""\
+            class Foo:{linebreaks}\
+                def bar(self):
+                    return 42{linebreaks}
+            {linebreaks}
+            """
+        ),
+        spec=RecipeSpec()
+        .with_recipes(
+            from_visitor(RemoveTrailingWhitespaceVisitor())
+        )
+    )
+
+
+@pytest.mark.parametrize('n_spaces', list(range(0, 4)))
+@pytest.mark.parametrize('linebreaks', ['\n', '\r\n', '\r\n\n', '\n\n'])
+def test_tabs_to_spaces_with_trailing_comma(n_spaces, linebreaks):
+    # noinspection PyInconsistentIndentation
+    spaces = ' ' * n_spaces
+    rewrite_run(
+        python(
+            # language=python
+            f"""\
+            def bar():{spaces}{linebreaks}\
+                return [
+                    1,{spaces}{linebreaks}\
+                    2,
+                    3,{spaces}{linebreaks}\
+                ]
+            {spaces}{linebreaks}
+            """,
+            # language=python
+            f"""\
+            def bar():{linebreaks}\
+                return [
+                    1,{linebreaks}\
+                    2,
+                    3,{linebreaks}\
+                ]
+            {linebreaks}
+            """
+        ),
+        spec=RecipeSpec()
+        .with_recipes(
+            from_visitor(RemoveTrailingWhitespaceVisitor())
+        )
+    )