Add Pypi download URL support

Signed-off-by: Tushar Goel <[email protected]>

Author: TG1999

src/fetchcode/__init__.py

@@ -44,6 +44,7 @@ def fetch_http(url, location):
     `url` URL string saving the content in a file at `location`
     """
     r = requests.get(url)
+
     with open(location, "wb") as f:
         f.write(r.content)
 
@@ -106,3 +107,17 @@ def fetch(url):
         return fetchers.get(scheme)(url, location)
 
     raise Exception("Not a supported/known scheme.")
+
+
+def fetch_json_response(url):
+    """
+    Fetch a JSON response from the given URL and return the parsed JSON data.
+    """
+    response = requests.get(url)
+    if response.status_code != 200:
+        raise Exception(f"Failed to fetch {url}: {response.status_code} {response.reason}")
+
+    try:
+        return response.json()
+    except ValueError as e:
+        raise Exception(f"Failed to parse JSON from {url}: {str(e)}")

src/fetchcode/download_urls.py

@@ -0,0 +1,41 @@
+# fetchcode is a free software tool from nexB Inc. and others.
+# Visit https://github.com/aboutcode-org/fetchcode for support and download.
+#
+# Copyright (c) nexB Inc. and others. All rights reserved.
+# http://nexb.com and http://aboutcode.org
+#
+# This software is licensed under the Apache License version 2.0.
+#
+# You may not use this software except in compliance with the License.
+# You may obtain a copy of the License at:
+# http://apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software distributed
+# under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+# CONDITIONS OF ANY KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations under the License.
+
+from packageurl.contrib.route import NoRouteAvailable
+from packageurl.contrib.route import Router
+
+from fetchcode.pypi import Pypi
+
+package_registry = [
+    Pypi,
+]
+
+router = Router()
+
+for pkg_class in package_registry:
+    router.append(pattern=pkg_class.purl_pattern, endpoint=pkg_class.get_download_url)
+
+
+def download_url(purl):
+    """
+    Return package metadata for a URL or PURL.
+    Return None if there is no URL, or the URL or PURL is not supported.
+    """
+    if purl:
+        try:
+            return router.process(purl)
+        except NoRouteAvailable:
+            return

src/fetchcode/pypi.py

@@ -0,0 +1,62 @@
+# fetchcode is a free software tool from nexB Inc. and others.
+# Visit https://github.com/aboutcode-org/fetchcode for support and download.
+#
+# Copyright (c) nexB Inc. and others. All rights reserved.
+# http://nexb.com and http://aboutcode.org
+#
+# This software is licensed under the Apache License version 2.0.
+#
+# You may not use this software except in compliance with the License.
+# You may obtain a copy of the License at:
+# http://apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software distributed
+# under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+# CONDITIONS OF ANY KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations under the License.
+
+from urllib.parse import urljoin
+
+from packageurl import PackageURL
+
+from fetchcode import fetch_json_response
+
+
+class Pypi:
+    """
+    This class handles Cargo PURLs.
+    """
+
+    purl_pattern = "pkg:pypi/.*"
+    base_url = "https://pypi.org/pypi/"
+
+    @classmethod
+    def get_download_url(cls, purl):
+        """
+        Return the download URL for a Pypi PURL.
+        """
+        purl = PackageURL.from_string(purl)
+
+        name = purl.name
+        version = purl.version
+
+        if not name or not version:
+            raise ValueError("Pypi PURL must specify a name and version")
+
+        url = urljoin(cls.base_url, f"{name}/{version}.json")
+
+        data = fetch_json_response(url)
+
+        download_urls = data.get("urls", [{}])
+
+        if not download_urls:
+            raise ValueError(f"No download URLs found for {name} version {version}")
+        
+        download_url = next(
+            (url["url"] for url in download_urls if url.get("url")),
+            None
+        )
+
+        if not download_url:
+            raise ValueError(f"No download URL found for {name} version {version}")
+
+        return download_url

tests/test_pypi.py

@@ -0,0 +1,80 @@
+import unittest
+from unittest.mock import patch
+from fetchcode.pypi import Pypi
+
+class TestGetDownloadURL(unittest.TestCase):
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_valid_purl_returns_download_url(self, mock_fetch_json_response):
+        mock_response = {
+            "urls": [
+                {
+                    "url": "https://files.pythonhosted.org/packages/source/r/requests/requests-2.31.0.tar.gz"
+                }
+            ]
+        }
+        mock_fetch_json_response.return_value = mock_response
+
+        purl = "pkg:pypi/[email protected]"
+        result = Pypi.get_download_url(purl)
+        self.assertEqual(
+            result,
+            "https://files.pythonhosted.org/packages/source/r/requests/requests-2.31.0.tar.gz"
+        )
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_missing_version_raises_value_error(self, mock_fetch_json_response):
+        purl = "pkg:pypi/requests"
+        with self.assertRaises(ValueError) as context:
+            Pypi.get_download_url(purl)
+        self.assertIn("Pypi PURL must specify a name and version", str(context.exception))
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_missing_name_raises_value_error(self, mock_fetch_json_response):
+        purl = "pkg:pypi/@2.31.0"
+        with self.assertRaises(ValueError) as context:
+            Pypi.get_download_url(purl)
+        self.assertIn("purl is missing the required name component", str(context.exception))
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_missing_urls_field_raises_value_error(self, mock_fetch_json_response):
+        mock_fetch_json_response.return_value = {}
+        purl = "pkg:pypi/[email protected]"
+        with self.assertRaises(ValueError) as context:
+            Pypi.get_download_url(purl)
+        self.assertIn("No download URL found", str(context.exception))
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_empty_urls_list_raises_value_error(self, mock_fetch_json_response):
+        mock_fetch_json_response.return_value = {"urls": []}
+        purl = "pkg:pypi/[email protected]"
+        with self.assertRaises(ValueError) as context:
+            Pypi.get_download_url(purl)
+        self.assertIn("No download URLs found", str(context.exception))
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_first_url_object_missing_url_key(self, mock_fetch_json_response):
+        mock_fetch_json_response.return_value = {
+            "urls": [{}]
+        }
+        purl = "pkg:pypi/[email protected]"
+        with self.assertRaises(ValueError) as context:
+            Pypi.get_download_url(purl)
+        self.assertIn("No download URL found", str(context.exception))
+
+    @patch("fetchcode.pypi.fetch_json_response")
+    def test_url_fallback_when_multiple_urls_provided(self, mock_fetch_json_response):
+        mock_fetch_json_response.return_value = {
+            "urls": [
+                {},
+                {"url": "https://example.com/fallback-url.tar.gz"}
+            ]
+        }
+
+        purl = "pkg:pypi/[email protected]"
+        download_url = Pypi.get_download_url(purl)
+        self.assertEqual(download_url, "https://example.com/fallback-url.tar.gz")
+
+    def test_malformed_purl_raises_exception(self):
+        with self.assertRaises(ValueError):
+            Pypi.get_download_url("this-is-not-a-valid-purl")