feat: add regex pattern extractor component (#6015)

* feat: add regex pattern extractor component

* [autofix.ci] apply automated fixes

* fix: consistent schema and cleaner code style

* fix: type annotation in regex.py

* [autofix.ci] apply automated fixes

* Fix: regex component unit tests to match implementation behavior

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Ítalo Johnny <italojohnnydosanjos@gmail.com>

src/backend/tests/unit/components/processing/test_regex_component.py

@@ -0,0 +1,95 @@
+import pytest
+from langflow.components.processing.regex import RegexExtractorComponent
+from langflow.schema import Data
+from langflow.schema.message import Message
+
+from tests.base import ComponentTestBaseWithoutClient
+
+
+class TestRegexExtractorComponent(ComponentTestBaseWithoutClient):
+    @pytest.fixture
+    def component_class(self):
+        """Return the component class to test."""
+        return RegexExtractorComponent
+
+    @pytest.fixture
+    def default_kwargs(self):
+        """Return the default kwargs for the component."""
+        return {
+            "input_text": "Contact us at test@example.com",
+            "pattern": r"\b\w+@\w+\.\w+\b",
+        }
+
+    @pytest.fixture
+    def file_names_mapping(self):
+        """Return an empty list since this component doesn't have version-specific files."""
+        return []
+
+    def test_successful_regex_extraction(self):
+        # Test with email pattern
+        component = RegexExtractorComponent(
+            input_text="Contact us at test@example.com or support@test.com", pattern=r"\b\w+@\w+\.\w+\b"
+        )
+
+        result = component.extract_matches()
+        assert isinstance(result, list)
+        assert all(isinstance(item, Data) for item in result)
+        assert len(result) == 2
+        assert result[0].data["match"] == "test@example.com"
+        assert result[1].data["match"] == "support@test.com"
+
+    def test_no_matches_found(self):
+        # Test with pattern that won't match
+        component = RegexExtractorComponent(input_text="No email addresses here", pattern=r"\b\w+@\w+\.\w+\b")
+
+        result = component.extract_matches()
+        assert isinstance(result, list)
+        assert len(result) == 0  # The implementation returns an empty list when no matches are found
+
+    def test_invalid_regex_pattern(self):
+        # Test with invalid regex pattern
+        component = RegexExtractorComponent(
+            input_text="Some text",
+            pattern="[",  # Invalid regex pattern
+        )
+
+        result = component.extract_matches()
+        assert isinstance(result, list)
+        assert len(result) == 1
+        assert "error" in result[0].data
+        assert "Invalid regex pattern" in result[0].data["error"]
+
+    def test_empty_input_text(self):
+        # Test with empty input
+        component = RegexExtractorComponent(input_text="", pattern=r"\b\w+@\w+\.\w+\b")
+
+        result = component.extract_matches()
+        assert isinstance(result, list)
+        assert len(result) == 0  # The implementation returns an empty list when input is empty
+
+    def test_get_matches_text_output(self):
+        # Test the text output method
+        component = RegexExtractorComponent(input_text="Contact: test@example.com", pattern=r"\b\w+@\w+\.\w+\b")
+
+        result = component.get_matches_text()
+        assert isinstance(result, Message)
+        assert result.text == "test@example.com"
+
+    def test_get_matches_text_no_matches(self):
+        # Test text output with no matches
+        component = RegexExtractorComponent(input_text="No email addresses", pattern=r"\b\w+@\w+\.\w+\b")
+
+        result = component.get_matches_text()
+        assert isinstance(result, Message)
+        assert result.text == "No matches found"
+
+    def test_get_matches_text_invalid_pattern(self):
+        # Test text output with invalid pattern
+        component = RegexExtractorComponent(
+            input_text="Some text",
+            pattern="[",  # Invalid regex pattern
+        )
+
+        result = component.get_matches_text()
+        assert isinstance(result, Message)
+        assert "Invalid regex pattern" in result.text