feat: allow mime_type to be guessed for ByteStream (#9573)

* feat(bytestream): add guess_mime_type parameter

* refactor(FileTypeRouter): refactor guess mimetype

* feat(bytestream): add guess_mime_type to util

* style(ruff): add trailing whitespace

* fix: fix type annotation

* test(file_type_router): add test for additional_mimetypes param

* fix(file_type_router): non-existent file behavior

* feat(file_type_router): add release notes

* fix(file_type_router): remove unused logger

* style: fix ruff formatting magic values

* test(bytestream): handle windows/unix mimetype differences

---------

Co-authored-by: Julian Risch <julian.risch@deepset.ai>

Author: kanenorman

haystack/components/converters/utils.py

@@ -8,20 +8,22 @@
 from haystack.dataclasses import ByteStream
 
 
-def get_bytestream_from_source(source: Union[str, Path, ByteStream]) -> ByteStream:
+def get_bytestream_from_source(source: Union[str, Path, ByteStream], guess_mime_type: bool = False) -> ByteStream:
     """
     Creates a ByteStream object from a source.
 
     :param source:
         A source to convert to a ByteStream. Can be a string (path to a file), a Path object, or a ByteStream.
+    :param guess_mime_type:
+        Whether to guess the mime type from the file.
     :return:
         A ByteStream object.
     """
 
     if isinstance(source, ByteStream):
         return source
     if isinstance(source, (str, Path)):
-        bs = ByteStream.from_file_path(Path(source))
+        bs = ByteStream.from_file_path(Path(source), guess_mime_type=guess_mime_type)
         bs.meta["file_path"] = str(source)
         return bs
     raise ValueError(f"Unsupported source type {type(source)}")

haystack/components/routers/file_type_router.py

@@ -12,15 +12,6 @@
 from haystack.components.converters.utils import get_bytestream_from_source, normalize_metadata
 from haystack.dataclasses import ByteStream
 
-CUSTOM_MIMETYPES = {
-    # we add markdown because it is not added by the mimetypes module
-    # see https://github.com/python/cpython/pull/17995
-    ".md": "text/markdown",
-    ".markdown": "text/markdown",
-    # we add msg because it is not added by the mimetypes module
-    ".msg": "application/vnd.ms-outlook",
-}
-
 
 @component
 class FileTypeRouter:
@@ -149,7 +140,7 @@ def run(
                 source = Path(source)
 
             if isinstance(source, Path):
-                mime_type = self._get_mime_type(source)
+                mime_type = ByteStream._guess_mime_type(source)
             elif isinstance(source, ByteStream):
                 mime_type = source.mime_type
             else:
@@ -171,16 +162,3 @@ def run(
                 mime_types["unclassified"].append(source)
 
         return dict(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.
-
-        :returns: The MIME type of the provided file path, or `None` if the MIME type cannot be determined.
-        """
-        extension = path.suffix.lower()
-        mime_type = mimetypes.guess_type(path.as_posix())[0]
-        # lookup custom mappings if the mime type is not found
-        return CUSTOM_MIMETYPES.get(extension, mime_type)

haystack/dataclasses/byte_stream.py

@@ -2,6 +2,7 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+import mimetypes
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, Dict, Optional
@@ -32,15 +33,22 @@ def to_file(self, destination_path: Path) -> None:
 
     @classmethod
     def from_file_path(
-        cls, filepath: Path, mime_type: Optional[str] = None, meta: Optional[Dict[str, Any]] = None
+        cls,
+        filepath: Path,
+        mime_type: Optional[str] = None,
+        meta: Optional[Dict[str, Any]] = None,
+        guess_mime_type: bool = False,
     ) -> "ByteStream":
         """
         Create a ByteStream from the contents read from a file.
 
         :param filepath: A valid path to a file.
         :param mime_type: The mime type of the file.
         :param meta: Additional metadata to be stored with the ByteStream.
+        :param guess_mime_type: Whether to guess the mime type from the file.
         """
+        if not mime_type and guess_mime_type:
+            mime_type = cls._guess_mime_type(filepath)
         with open(filepath, "rb") as fd:
             return cls(data=fd.read(), mime_type=mime_type, meta=meta or {})
 
@@ -100,3 +108,26 @@ def from_dict(cls, data: Dict[str, Any]) -> "ByteStream":
         :returns: A ByteStream instance.
         """
         return ByteStream(data=bytes(data["data"]), meta=data.get("meta", {}), mime_type=data.get("mime_type"))
+
+    @staticmethod
+    def _guess_mime_type(path: Path) -> Optional[str]:
+        """
+        Guess the MIME type of the provided file path.
+
+        :param path: The file path to get the MIME type for.
+
+        :returns: The MIME type of the provided file path, or `None` if the MIME type cannot be determined.
+        """
+        custom_mimetypes = {
+            # we add markdown because it is not added by the mimetypes module
+            # see https://github.com/python/cpython/pull/17995
+            ".md": "text/markdown",
+            ".markdown": "text/markdown",
+            # we add msg because it is not added by the mimetypes module
+            ".msg": "application/vnd.ms-outlook",
+        }
+
+        extension = path.suffix.lower()
+        mime_type = mimetypes.guess_type(path.as_posix())[0]
+        # lookup custom mappings if the mime type is not found
+        return custom_mimetypes.get(extension, mime_type)

releasenotes/notes/add-bytestream-guess-mime-type-e973262fa75f2982.yaml

@@ -0,0 +1,4 @@
+---
+enhancements:
+  - |
+    Add `guess_mime_type` parameter to `Bytestream.from_file_path()`

test/components/converters/test_utils.py

@@ -4,7 +4,8 @@
 
 import pytest
 
-from haystack.components.converters.utils import normalize_metadata
+from haystack.components.converters.utils import get_bytestream_from_source, normalize_metadata
+from haystack.dataclasses import ByteStream
 
 
 def test_normalize_metadata_None():
@@ -32,3 +33,40 @@ def test_normalize_metadata_list_of_wrong_size():
 def test_normalize_metadata_other_type():
     with pytest.raises(ValueError, match="meta must be either None, a dictionary or a list of dictionaries."):
         normalize_metadata(({"a": 1},), sources_count=1)
+
+
+def test_get_bytestream_from_path_object(tmp_path):
+    bytes_ = b"hello world"
+    source = tmp_path / "test.txt"
+    source.write_bytes(bytes_)
+
+    bs = get_bytestream_from_source(source, guess_mime_type=True)
+
+    assert isinstance(bs, ByteStream)
+    assert bs.data == bytes_
+    assert bs.mime_type == "text/plain"
+    assert bs.meta["file_path"].endswith("test.txt")
+
+
+def test_get_bytestream_from_string_path(tmp_path):
+    bytes_ = b"hello world"
+    source = tmp_path / "test.txt"
+    source.write_bytes(bytes_)
+
+    bs = get_bytestream_from_source(str(source), guess_mime_type=True)
+
+    assert isinstance(bs, ByteStream)
+    assert bs.data == bytes_
+    assert bs.mime_type == "text/plain"
+    assert bs.meta["file_path"].endswith("test.txt")
+
+
+def test_get_bytestream_from_source_invalid_type():
+    with pytest.raises(ValueError, match="Unsupported source type"):
+        get_bytestream_from_source(123)
+
+
+def test_get_bytestream_from_source_bytestream_passthrough():
+    bs = ByteStream(data=b"spam", mime_type="text/custom", meta={"spam": "eggs"})
+    result = get_bytestream_from_source(bs)
+    assert result is bs

test/components/routers/test_file_router.py

@@ -3,11 +3,15 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import io
+import mimetypes
 import sys
+from pathlib import PosixPath
 from unittest.mock import mock_open, patch
 
 import pytest
+from packaging import version
 
+import haystack
 from haystack import Pipeline
 from haystack.components.converters import PyPDFToDocument, TextFileToDocument
 from haystack.components.routers.file_type_router import FileTypeRouter
@@ -395,3 +399,50 @@ def test_pipeline_with_converters(self, test_files_path):
 
         assert output["text_file_converter"]["documents"][0].meta["meta_field_1"] == "meta_value_1"
         assert output["pypdf_converter"]["documents"][0].meta["meta_field_2"] == "meta_value_2"
+
+    def test_additional_mimetypes_integration(self, tmp_path):
+        """
+        Test if the component runs correctly in a pipeline with additional mimetypes correctly.
+        """
+        custom_mime_type = "application/x-spam"
+        custom_extension = ".spam"
+        test_file = tmp_path / f"test.{custom_extension}"
+        test_file.touch()
+
+        # confirm that mimetypes module doesn't know about this extension by default
+        assert custom_mime_type not in mimetypes.types_map.values()
+
+        # make haystack aware of the custom mime type
+        router = FileTypeRouter(
+            mime_types=[custom_mime_type], additional_mimetypes={custom_mime_type: custom_extension}
+        )
+        mappings = router.run(sources=[test_file])
+
+        # assert the file was classified under the custom mime type
+        assert custom_mime_type in mappings
+        assert test_file in mappings[custom_mime_type]
+
+    @pytest.mark.skipif(
+        version.parse(haystack.__version__) >= version.parse("2.17.0"),
+        reason="https://github.com/deepset-ai/haystack/pull/9573#issuecomment-3045237341",
+    )
+    def test_non_existent_file(self):
+        """
+        Test conditional FileNotFoundError behavior in FileTypeRouter.
+
+        In Haystack versions prior to 2.17.0, `FileTypeRouter` does not raise an error
+        when a non-existent file is passed without `meta`. However, it raises a
+        FileNotFoundError when the same file is passed with `meta` supplied.
+
+        This inconsistent behavior is slated to change in 2.17.0.
+        See: https://github.com/deepset-ai/haystack/pull/9573#issuecomment-3045237341
+        """
+        router = FileTypeRouter(mime_types=[r"text/plain"])
+
+        # No meta - does not raise error
+        result = router.run(sources=["non_existent.txt"])
+        assert result == {"text/plain": [PosixPath("non_existent.txt")]}
+
+        # With meta - raises FileNotFoundError
+        with pytest.raises(FileNotFoundError):
+            router.run(sources=["non_existent.txt"], meta={"spam": "eggs"})

test/dataclasses/test_byte_stream.py

@@ -26,6 +26,52 @@ def test_from_file_path(tmp_path, request):
     assert b.meta == {"foo": "bar"}
 
 
+@pytest.mark.parametrize(
+    "file_path, expected_mime_types",
+    [
+        ("spam.jpeg", {"image/jpeg"}),
+        ("spam.jpg", {"image/jpeg"}),
+        ("spam.png", {"image/png"}),
+        ("spam.gif", {"image/gif"}),
+        ("spam.svg", {"image/svg+xml"}),
+        ("spam.js", {"text/javascript", "application/javascript"}),
+        ("spam.txt", {"text/plain"}),
+        ("spam.html", {"text/html"}),
+        ("spam.htm", {"text/html"}),
+        ("spam.css", {"text/css"}),
+        ("spam.csv", {"text/csv"}),
+        ("spam.md", {"text/markdown"}),  # custom mapping
+        ("spam.markdown", {"text/markdown"}),  # custom mapping
+        ("spam.msg", {"application/vnd.ms-outlook"}),  # custom mapping
+        ("spam.pdf", {"application/pdf"}),
+        ("spam.xml", {"application/xml", "text/xml"}),
+        ("spam.json", {"application/json"}),
+        ("spam.doc", {"application/msword"}),
+        ("spam.docx", {"application/vnd.openxmlformats-officedocument.wordprocessingml.document"}),
+        ("spam.xls", {"application/vnd.ms-excel"}),
+        ("spam.xlsx", {"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"}),
+        ("spam.ppt", {"application/vnd.ms-powerpoint"}),
+        ("spam.pptx", {"application/vnd.openxmlformats-officedocument.presentationml.presentation"}),
+    ],
+)
+def test_from_file_path_guess_mime_type(file_path, expected_mime_types, tmp_path):
+    test_file = tmp_path / file_path
+    test_file.touch()
+
+    b = ByteStream.from_file_path(test_file, guess_mime_type=True)
+    assert b.mime_type in expected_mime_types
+
+
+def test_explicit_mime_type_is_not_overwritten_by_guessing(tmp_path):
+    # create empty file with correct extension
+    test_file = tmp_path / "sample.md"
+    test_file.touch()
+
+    explicit_mime_type = "text/x-rst"
+    b = ByteStream.from_file_path(test_file, mime_type=explicit_mime_type, guess_mime_type=True)
+    assert b.mime_type == explicit_mime_type
+
+
 def test_from_string():
     test_string = "Hello, world!"
     b = ByteStream.from_string(test_string)