[Python] Return every group from Regex.all_matches

CHANGES.md

@@ -82,6 +82,7 @@
   `valueMapper`, `topicNameMapper`, or providing a `ConnectionFactory` must update imports from `javax.jms.*` to
   `jakarta.jms.*`. The module now requires Java 17 at runtime ([#38729](https://github.com/apache/beam/issues/38729)).
 * (Python) `Regex.find_all` with `group=Regex.ALL` now returns every group, as `(match, group1, group2, ...)`, instead of only group 1, and with `outputEmpty=False` it drops a match only when the whole match is empty, matching the `group=0` behavior ([#40399](https://github.com/apache/beam/pull/40399)).
+* (Python) `Regex.all_matches` now returns every group of the regex, instead of failing with a `TypeError` when the regex has no groups and dropping nested or unmatched trailing groups ([#40562](https://github.com/apache/beam/issues/40562)).
 
 ## Deprecations
 

sdks/python/apache_beam/transforms/util.py

@@ -2156,7 +2156,9 @@ def _process(element):
   def all_matches(pcoll, regex):
     """
     Returns all matches (groups) if zero or more characters at the beginning
-    of string match the regular expression.
+    of string match the regular expression. Each output is a list of the
+    entire match followed by every group of the regex, with None for a group
+    that did not participate in the match.
 
     Args:
       regex: the regular expression string or (re.compile) pattern.
@@ -2166,7 +2168,7 @@ def all_matches(pcoll, regex):
     def _process(element):
       m = regex.match(element)
       if m:
-        yield [m.group(ix) for ix in range(m.lastindex + 1)]
+        yield [m.group(), *m.groups()]
 
     return pcoll | FlatMap(_process)
 

sdks/python/apache_beam/transforms/util_test.py

@@ -2854,6 +2854,22 @@ def test_all_matched_pattern(self):
                          ["z z", "z", "z"]]
       assert_that(result, equal_to(expected_result))
 
+  def test_all_matched_returns_every_group(self):
+    with TestPipeline() as p:
+      pcol = (p | beam.Create(["ab"]))
+      assert_that(
+          pcol | 'nested groups' >> util.Regex.all_matches("((a)(b))"),
+          equal_to([["ab", "ab", "a", "b"]]),
+          label='CheckNestedGroups')
+      assert_that(
+          pcol | 'optional group' >> util.Regex.all_matches("(a)(c)?"),
+          equal_to([["a", "a", None]]),
+          label='CheckOptionalGroup')
+      assert_that(
+          pcol | 'no groups' >> util.Regex.all_matches("a+"),
+          equal_to([["a"]]),
+          label='CheckNoGroups')
+
   def test_match_group_kv(self):
     with TestPipeline() as p:
       result = (