Fix parsers.re doing only partial string match

CHANGES.rst

@@ -5,6 +5,7 @@ Unreleased
 ----------
 - Fix bug where steps without parsers would take precedence over steps with parsers. `#534 <https://github.com/pytest-dev/pytest-bdd/pull/534>`_
 - Step functions can now be decorated multiple times with @given, @when, @then. Previously every decorator would override ``converters`` and ``target_fixture`` every at every application. `#534 <https://github.com/pytest-dev/pytest-bdd/pull/534>`_ `#525 <https://github.com/pytest-dev/pytest-bdd/issues/525>`_
+- ``parsers.re`` now does a `fullmatch <https://docs.python.org/3/library/re.html#re.fullmatch>`_ instead of a partial match. This is to make it work just like the other parsers, since they don't ignore non-matching characters at the end of the string. `#539 <https://github.com/pytest-dev/pytest-bdd/pull/539>`_
 
 6.0.1
 -----

pytest_bdd/parsers.py

@@ -42,14 +42,14 @@ def parse_arguments(self, name: str) -> dict[str, str] | None:
 
         :return: `dict` of step arguments
         """
-        match = self.regex.match(name)
+        match = self.regex.fullmatch(name)
         if match is None:
             return None
         return match.groupdict()
 
     def is_matching(self, name: str) -> bool:
         """Match given name with the step name."""
-        return bool(self.regex.match(name))
+        return bool(self.regex.fullmatch(name))
 
 
 class parse(StepParser):

tests/args/regex/test_args.py

@@ -14,7 +14,7 @@ def test_every_steps_takes_param_with_the_same_name(testdir):
                     When I pay 2 Euro
                     And I pay 1 Euro
                     Then I should have 0 Euro
-                    And I should have 999999 Euro # In my dream...
+                    And I should have 999999 Euro
 
             """
         ),
@@ -55,6 +55,59 @@ def i_should_have(euro, values):
     result.assert_outcomes(passed=1)
 
 
+def test_exact_match(testdir):
+    """Test that parsers.re does an exact match (fullmatch) of the whole string.
+
+    This tests exists because in the past we only used re.match, which only finds a match at the beginning
+    of the string, so if there were any more characters not matching at the end, they were ignored"""
+
+    testdir.makefile(
+        ".feature",
+        arguments=textwrap.dedent(
+            """\
+            Feature: Step arguments
+                Scenario: Every step takes a parameter with the same name
+                    Given I have 2 Euro
+                    # Step that should not be found:
+                    When I pay 1 Euro by mistake
+                    Then I should have 1 Euro left
+            """
+        ),
+    )
+
+    testdir.makepyfile(
+        textwrap.dedent(
+            r"""
+        import pytest
+        from pytest_bdd import parsers, given, when, then, scenarios
+
+        scenarios("arguments.feature")
+
+        @given(parsers.re(r"I have (?P<amount>\d+) Euro"), converters={"amount": int}, target_fixture="wallet")
+        def _(amount):
+            return {"EUR": amount}
+
+
+        # Purposefully using a re that will not match the step "When I pay 1 Euro and 50 cents"
+        @when(parsers.re(r"I pay (?P<amount>\d+) Euro"), converters={"amount": int})
+        def _(amount, wallet):
+            wallet["EUR"] -= amount
+
+
+        @then(parsers.re(r"I should have (?P<amount>\d+) Euro left"), converters={"amount": int})
+        def _(amount, wallet):
+            assert wallet["EUR"] == amount
+
+        """
+        )
+    )
+    result = testdir.runpytest()
+    result.assert_outcomes(failed=1)
+    result.stdout.fnmatch_lines(
+        '*StepDefinitionNotFoundError: Step definition is not found: When "I pay 1 Euro by mistake"*'
+    )
+
+
 def test_argument_in_when(testdir):
     testdir.makefile(
         ".feature",