Prevent repeated whitespace items in arrays (#406)

* prevent repeated whitespace items

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: DimmaDont

tests/test_items.py

@@ -1008,3 +1008,14 @@ def add_table(parent, name):
     add_table(root, "first")
     add_table(root, "second")
     assert doc.as_string() == "[root.first]\n\n[root.second]\n"
+
+
+def test_removal_of_arrayitem_with_extra_whitespace():
+    expected = 'x = [\n    "bar",\n]'
+    doc = parse('x = [\n    "foo" ,#spam\n    "bar",\n]')
+    x = doc["x"]
+    assert isinstance(x, Array)
+    x.remove("foo")
+    docstr = doc.as_string()
+    parse(docstr)
+    assert docstr == expected

tomlkit/parser.py

@@ -595,7 +595,15 @@ def _parse_array(self) -> Array:
             # consume comma
             if prev_value and self._current == ",":
                 self.inc(exception=UnexpectedEofError)
-                elems.append(Whitespace(","))
+                # Check if the previous item is Whitespace
+                if isinstance(elems[-1], Whitespace) and " " in elems[-1].s:
+                    # Preserve the previous whitespace
+                    comma = Whitespace(elems[-1].s + ",")
+                    # Remove the replaced item
+                    del elems[-1]
+                else:
+                    comma = Whitespace(",")
+                elems.append(comma)
                 prev_value = False
                 continue