feat(download): add session adapter for local files

src/debsbom/commands/download.py

@@ -18,6 +18,7 @@
     from zstandard import ZstdCompressor, ZstdDecompressor
     import requests
     from ..snapshot import client as sdlclient
+    from ..download.adapters import LocalFileAdapter
     from ..download.download import PackageDownloader
     from ..download.resolver import PersistentResolverCache, UpstreamResolver
     from debsbom.download.download import DownloadStatus, DownloadResult
@@ -77,6 +78,7 @@ def run(cls, args):
         else:
             resolver = cls.get_pkgstream_resolver()
         rs = requests.Session()
+        rs.mount("file:///", LocalFileAdapter())
         rs.headers.update({"User-Agent": f"debsbom/{version('debsbom')}"})
         sdl = sdlclient.SnapshotDataLake(session=rs)
         u_resolver = UpstreamResolver(sdl, cache)

src/debsbom/download/adapters.py

@@ -0,0 +1,44 @@
+# Copyright (C) 2025 Siemens
+#
+# SPDX-License-Identifier: MIT
+
+import errno
+from io import BytesIO
+import locale
+from pathlib import Path
+from requests import Response, Request, Session, codes
+from requests.adapters import BaseAdapter
+from urllib.parse import unquote, urlparse
+
+
+class LocalFileAdapter(BaseAdapter):
+    """Adapter for local file access."""
+
+    def send(self, request, **kwargs) -> Response:
+        if request.method != "GET":
+            raise ValueError(f"Request method {request.method} is not supported")
+
+        response = Response()
+        response.request = request
+        response.url = request.url
+
+        path = Path(unquote(urlparse(request.url).path))
+        try:
+            response.raw = open(path, "rb")
+            # make sure we properly close the file when we are done
+            response.raw.release_conn = response.raw.close
+            response.status_code = codes.ok
+        except IOError as e:
+            if e.errno == errno.EACCES:
+                response.status_code = codes.forbidden
+            elif e.errno == errno.ENOENT:
+                response.status_code = codes.not_found
+            else:
+                response.status_code = codes.bad_request
+            response.raw = BytesIO(str(e).encode(locale.getpreferredencoding()))
+            response.reason = str(e)
+
+        return response
+
+    def close(self):
+        pass

tests/data/local-download

@@ -0,0 +1 @@
+This is a test file for the local file adapter test.

tests/test_download.py

@@ -8,6 +8,7 @@
 import jsonschema
 
 import pytest
+from debsbom.download.adapters import LocalFileAdapter
 from debsbom.download import (
     PackageDownloader,
     PersistentResolverCache,
@@ -31,6 +32,7 @@
 import spdx_tools.spdx.writer.json.json_writer as spdx_json_writer
 import cyclonedx.output as cdx_output
 import cyclonedx.schema as cdx_schema
+from requests import Session
 
 from unittest import mock
 
@@ -291,3 +293,18 @@ def test_download_result_invalid(dlschema):
     }
     with pytest.raises(jsonschema.ValidationError):
         jsonschema.validate(data, schema=dlschema)
+
+
+def test_local_file():
+    session = Session()
+    session.mount("file:///", LocalFileAdapter())
+    with session.get("file://" + str(Path("tests/data/local-download").absolute())) as r:
+        assert r.status_code == 200
+        assert r.content == b"This is a test file for the local file adapter test.\n"
+
+
+def test_local_file_404():
+    session = Session()
+    session.mount("file:///", LocalFileAdapter())
+    with session.get("file:///does-not-exist") as r:
+        assert r.status_code == 404