ubuntutools/archive.py: fix crash in SourcePackage()._source_urls()

Fix operation of SourcePackage._source_urls() (as used, for example, in
SourcePackage.pull() called by backportpackage) to also work when the
class is instantiated with a URL as .dsc.

This is a regression caused by 1b12d8b4e3315de3bf417b40a3c66279f309d72c
(first in v0.184) that moved from os.path.join() to Pathlib, but
os.path.join() was also used to join URLs.

Thanks: Unit 193 for the initial patch.
Signed-off-by: Mattia Rizzolo <mattia@debian.org>

debian/changelog

@@ -1,7 +1,7 @@
 ubuntu-dev-tools (0.191) UNRELEASED; urgency=medium
 
-  [ Mattia Rizzolo ]
   * WIP.
+
   [ Dan Streetman ]
   * lpapicache:
     + Make sure that login() actually logins and doesn't use cached credentials.
@@ -10,8 +10,16 @@ ubuntu-dev-tools (0.191) UNRELEASED; urgency=medium
       operation mode from authenticated to anonymous.  LP: #1984113
 
   [ Stefano Rivera ]
-  * backportpackage: Add support for lsb-release-minimal, which doesn't have a
-    Python module, thanks Gioele Barabucci. (Closes: 1020901)
+  * backportpackage:
+    + Add support for lsb-release-minimal, which doesn't have a Python module.
+      Thanks to Gioele Barabucci for the patch.  Closes: #1020901
+
+  [ Mattia Rizzolo ]
+  * ubuntutools/archive.py:
+    + Fix operation of SourcePackage._source_urls() (as used, for example, in
+      SourcePackage.pull() called by backportpackage) to also work when the
+      class is instantiated with a URL as .dsc.  Fixes regression from v0.184.
+      Thanks to Unit 193 for the initial patch.
 
  -- Mattia Rizzolo <mattia@debian.org>  Mon, 22 Aug 2022 17:55:53 +0200
 

ubuntutools/archive.py

@@ -27,7 +27,7 @@ Approach:
 3. Verify checksums.
 """
 
-from urllib.request import urlopen
+from urllib.request import urlopen, urlparse, urljoin
 import codecs
 import functools
 import json
@@ -168,7 +168,9 @@ class SourcePackage(ABC):
         self._series = series
         self._pocket = pocket
         self._status = status
-        self._dsc_source = Path(dscfile) if dscfile else None
+        # dscfile can be either a path or an URL.  misc.py's download() will
+        # later fiture it out
+        self._dsc_source = dscfile
         self._verify_signature = verify_signature
 
         # Cached values:
@@ -323,7 +325,12 @@ class SourcePackage(ABC):
     def _source_urls(self, name):
         "Generator of sources for name"
         if self._dsc_source:
-            yield str(self._dsc_source.parent / name)
+            # we only take "" as file, as regardless if for some reason this
+            # is a file:// url we still need to handle it with urljoin
+            if urlparse(str(self._dsc_source)).scheme == "":
+                yield str(Path(self._dsc_source).parent / name)
+            else:
+                yield urljoin(self._dsc_source, name)
         for server in self._archive_servers():
             yield self._mirror_url(server, self.component, name)
         if self.lp_spph.sourceFileUrl(name):