Fix empty regex matching with csvgrep any-match

CHANGELOG.rst

@@ -1,6 +1,7 @@
 Unreleased
 ----------
 
+-  fix: :doc:`/scripts/csvgrep` treats an empty :code:`--regex` as a pattern that matches every value, including with :code:`--any-match` and :code:`--invert-match`.
 -  feat: :doc:`/scripts/csvcut` adds an :code:`--ignore-unknown-columns` option to skip identifiers in :code:`-c/--columns` that do not match a column in the input.
 -  feat: :doc:`/scripts/csvclean` adds a :code:`--remove-empty-columns` option to remove empty columns from standard output.
 -  feat: :doc:`/scripts/in2csv` guesses the ``ndjson`` format for files with :code:`.ndjson`, :code:`.jsonl` and :code:`.jl` extensions.

csvkit/utilities/csvgrep.py

@@ -60,7 +60,7 @@ def main(self):
 
         rows, column_names, column_ids = self.get_rows_and_column_names_and_column_ids(**reader_kwargs)
 
-        if self.args.regex:
+        if self.args.regex is not None:
             pattern = re.compile(self.args.regex)
         elif self.args.matchfile:
             lines = {line.rstrip() for line in self.args.matchfile}

tests/test_utilities/test_csvgrep.py

@@ -69,6 +69,20 @@ def test_re_match(self):
             ['1', '2', '3'],
         ])
 
+    def test_empty_regex(self):
+        for any_match in (False, True):
+            for inverse in (False, True):
+                with self.subTest(any_match=any_match, inverse=inverse):
+                    args = ['-c', '1,2', '-r', '', 'examples/dummy.csv']
+                    if any_match:
+                        args.append('--any-match')
+                    if inverse:
+                        args.append('--invert-match')
+                    expected = [['a', 'b', 'c']]
+                    if not inverse:
+                        expected.append(['1', '2', '3'])
+                    self.assertRows(args, expected)
+
     def test_re_match_utf8(self):
         self.assertRows(['-c', '3', '-r', 'ʤ', 'examples/test_utf8.csv'], [
             ['foo', 'bar', 'baz'],