feat: Add FileExtensionClassifier to previews (#5514)

* Add FileExtensionClassifier preview component

* Add release note

* PR feedback

haystack/preview/components/__init__.py

@@ -1,3 +1,4 @@
 from haystack.preview.components.audio.whisper_local import LocalWhisperTranscriber
 from haystack.preview.components.audio.whisper_remote import RemoteWhisperTranscriber
 from haystack.preview.components.file_converters import TextFileToDocument
+from haystack.preview.components.classifiers import FileExtensionClassifier

haystack/preview/components/classifiers/__init__.py

@@ -0,0 +1 @@
+from haystack.preview.components.classifiers.file_classifier import FileExtensionClassifier

haystack/preview/components/classifiers/file_classifier.py

@@ -0,0 +1,82 @@
+import logging
+import mimetypes
+from collections import defaultdict
+from pathlib import Path
+from typing import List, Union, Optional
+
+from haystack.preview import component
+
+logger = logging.getLogger(__name__)
+
+
+@component
+class FileExtensionClassifier:
+    """
+    A component that classifies files based on their MIME types read from their file extensions. This component
+    does not read the file contents, but rather uses the file extension to determine the MIME type of the file.
+
+    The FileExtensionClassifier takes a list of file paths and groups them by their MIME types.
+    The list of MIME types to consider is provided during the initialization of the component.
+
+    This component is particularly useful when working with a large number of files, and you
+    want to categorize them based on their MIME types.
+    """
+
+    def __init__(self, mime_types: List[str]):
+        """
+        Initialize the FileExtensionClassifier.
+
+        :param mime_types: A list of file mime types to consider when classifying
+        files (e.g. ["text/plain", "audio/x-wav", "image/jpeg"]).
+        """
+        if not mime_types:
+            raise ValueError("The list of mime types cannot be empty.")
+
+        all_known_mime_types = all(self.is_valid_mime_type_format(mime_type) for mime_type in mime_types)
+        if not all_known_mime_types:
+            raise ValueError(f"The list of mime types contains unknown mime types: {mime_types}")
+
+        # save the init parameters for serialization
+        self.init_parameters = {"mime_types": mime_types}
+
+        component.set_output_types(self, unclassified=List[Path], **{mime_type: List[Path] for mime_type in mime_types})
+        self.mime_types = mime_types
+
+    def run(self, paths: List[Union[str, Path]]):
+        """
+        Run the FileExtensionClassifier.
+
+        This method takes the input data, iterates through the provided file paths, checks the file
+        mime type of each file, and groups the file paths by their mime types.
+
+        :param paths: The input data containing the file paths to classify.
+        :return: The output data containing the classified file paths.
+        """
+        mime_types = defaultdict(list)
+        for path in paths:
+            if isinstance(path, str):
+                path = Path(path)
+            mime_type = self.get_mime_type(path)
+            if mime_type in self.mime_types:
+                mime_types[mime_type].append(path)
+            else:
+                mime_types["unclassified"].append(path)
+
+        return mime_types
+
+    def get_mime_type(self, path: Path) -> Optional[str]:
+        """
+        Get the MIME type of the provided file path.
+
+        :param path: The file path to get the MIME type for.
+        :return: The MIME type of the provided file path, or None if the MIME type cannot be determined.
+        """
+        return mimetypes.guess_type(path.as_posix())[0]
+
+    def is_valid_mime_type_format(self, mime_type: str) -> bool:
+        """
+        Check if the provided MIME type is in valid format
+        :param mime_type: The MIME type to check.
+        :return: True if the provided MIME type is a valid MIME type format, False otherwise.
+        """
+        return mime_type in mimetypes.types_map.values()

releasenotes/notes/add-file-extension-classifier-preview-40f31c27bbd7cff9.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Adds FileExtensionClassifier to preview components.

test/preview/components/classifiers/test_file_classifier.py

@@ -0,0 +1,89 @@
+import sys
+
+import pytest
+
+from haystack.preview.components.classifiers.file_classifier import FileExtensionClassifier
+from test.preview.components.base import BaseTestComponent
+from test.conftest import preview_samples_path
+
+
+@pytest.mark.skipif(
+    sys.platform in ["win32", "cygwin"],
+    reason="Can't run on Windows Github CI, need access to registry to get mime types",
+)
+class TestFileExtensionClassifier(BaseTestComponent):
+    @pytest.mark.unit
+    def test_save_load(self, tmp_path):
+        self.assert_can_be_saved_and_loaded_in_pipeline(
+            FileExtensionClassifier(mime_types=["text/plain", "audio/x-wav", "image/jpeg"]), tmp_path
+        )
+
+    @pytest.mark.unit
+    def test_run(self, preview_samples_path):
+        """
+        Test if the component runs correctly in the simplest happy path.
+        """
+        file_paths = [
+            preview_samples_path / "txt" / "doc_1.txt",
+            preview_samples_path / "txt" / "doc_2.txt",
+            preview_samples_path / "audio" / "the context for this answer is here.wav",
+            preview_samples_path / "images" / "apple.jpg",
+        ]
+
+        classifier = FileExtensionClassifier(mime_types=["text/plain", "audio/x-wav", "image/jpeg"])
+        output = classifier.run(paths=file_paths)
+        assert output
+        assert len(output["text/plain"]) == 2
+        assert len(output["audio/x-wav"]) == 1
+        assert len(output["image/jpeg"]) == 1
+        assert not output["unclassified"]
+
+    @pytest.mark.unit
+    def test_no_files(self):
+        """
+        Test that the component runs correctly when no files are provided.
+        """
+        classifier = FileExtensionClassifier(mime_types=["text/plain", "audio/x-wav", "image/jpeg"])
+        output = classifier.run(paths=[])
+        assert not output
+
+    @pytest.mark.unit
+    def test_unlisted_extensions(self, preview_samples_path):
+        """
+        Test that the component correctly handles files with non specified mime types.
+        """
+        file_paths = [
+            preview_samples_path / "txt" / "doc_1.txt",
+            preview_samples_path / "audio" / "ignored.mp3",
+            preview_samples_path / "audio" / "this is the content of the document.wav",
+        ]
+        classifier = FileExtensionClassifier(mime_types=["text/plain"])
+        output = classifier.run(paths=file_paths)
+        assert len(output["text/plain"]) == 1
+        assert "mp3" not in output
+        assert len(output["unclassified"]) == 2
+        assert str(output["unclassified"][0]).endswith("ignored.mp3")
+        assert str(output["unclassified"][1]).endswith("this is the content of the document.wav")
+
+    @pytest.mark.unit
+    def test_no_extension(self, preview_samples_path):
+        """
+        Test that the component ignores files with no extension.
+        """
+        file_paths = [
+            preview_samples_path / "txt" / "doc_1.txt",
+            preview_samples_path / "txt" / "doc_2",
+            preview_samples_path / "txt" / "doc_2.txt",
+        ]
+        classifier = FileExtensionClassifier(mime_types=["text/plain"])
+        output = classifier.run(paths=file_paths)
+        assert len(output["text/plain"]) == 2
+        assert len(output["unclassified"]) == 1
+
+    @pytest.mark.unit
+    def test_unknown_mime_type(self):
+        """
+        Test that the component handles files with unknown mime types.
+        """
+        with pytest.raises(ValueError, match="The list of mime types"):
+            FileExtensionClassifier(mime_types=["type_invalid"])