debian: Add missing file URIs in lister output

For a given package, the debian lister generates a dictionary mapping
distribution and version to a list of files to be processed by the
debian loader.

For each file to process, the debian loader expects to find an URI
in order to download it and then use its content to ingest package
source code into the archive.

However, it turns out these URIs were not computed by the lister
in its current implementation making any debian loading task fail
due to these missing info.

So add the computation of these URIS and ensure they will be provided
in the debian loader input parameters.

Related to T2400

swh/lister/debian/lister.py

@@ -11,6 +11,7 @@ import gzip
 from itertools import product
 import logging
 import lzma
+import os
 from typing import Any, Callable, Dict, Iterator, List, Optional, Set, Tuple
 from urllib.parse import urljoin
 
@@ -198,9 +199,12 @@ class DebianLister(Lister[DebianListerState, DebianPageType]):
                 if field_ in src_pkg:
                     for entry in src_pkg[field_]:
                         name = entry["name"]
-                        files[name]["name"] = entry["name"]
+                        files[name]["name"] = name
                         files[name]["size"] = int(entry["size"], 10)
                         files[name][sum_name] = entry[sum_name]
+                        files[name]["uri"] = os.path.join(
+                            self.url, src_pkg["Directory"], name
+                        )
 
             # extract package name and version
             package_name = src_pkg["Package"]

swh/lister/debian/tests/test_lister.py

@@ -4,6 +4,7 @@
 # See top-level LICENSE file for more information
 
 from collections import defaultdict
+import os
 from pathlib import Path
 from typing import Dict, List, Set, Tuple
 
@@ -117,11 +118,19 @@ def _check_listed_origins(
                     ]
 
                     assert filtered_origins
+                    packages = filtered_origins[0].extra_loader_arguments["packages"]
                     # check the version info are available
-                    assert (
-                        package_version_key
-                        in filtered_origins[0].extra_loader_arguments["packages"]
-                    )
+                    assert package_version_key in packages
+
+                    # check package files URIs are available
+                    for file in pkg_src["files"]:
+                        filename = file["name"]
+                        file_uri = os.path.join(
+                            _mirror_url, pkg_src["Directory"], filename
+                        )
+                        package_files = packages[package_version_key]["files"]
+                        assert filename in package_files
+                        assert package_files[filename]["uri"] == file_uri
 
                     # check listed package version is in lister state
                     assert package_name in lister.state.package_versions