Summary

Fix inline comment being included as the value when a key has an empty value.

Problem

WITH_VALUE=hello # comment   ->  'hello'    ✓ correct
EMPTY_VALUE= # comment       ->  '# comment' ✗ wrong (should be '')
JUST_EMPTY=                  ->  ''           ✓ correct

Root cause

In parse_value(), after the = sign and trailing whitespace are consumed by _equal_sign, the next character is checked:

elif char in ('', '\n', '\r'):
    return ''

When the value is KEY= # comment, after = is consumed, the next char is #. Since # isn't in the check, it falls through to parse_unquoted_value(), which captures # comment as the value. The regex \s+#.* in parse_unquoted_value can't strip it because the # is at the start — there's no whitespace before it.

Fix

-    elif char in ('', '\n', '\r'):
+    elif char in ('', '\n', '\r', '#'):
         return ''

Adding # to the empty-value check ensures that when the value position starts with #, it's recognized as an inline comment and the value is returned as empty. The comment itself is then properly consumed by reader.read_regex(_comment) in parse_binding().

Fixes #600