Bug#1138082: apt: Inconsistent documentation on the usage of comma/space delimiters in DEB-822 sources

Package: apt
Version: 3.2.0
X-Debbugs-CC: [email protected]

Greetings APT developers,

Whilst maintaining oma (https://github.com/AOSC-Dev/oma), a package 
management frontend based on libapt-pkg, we ran into multiple user 
reports that oma is unable to handled comma-separated items in the 
"Architectures:" entry.

Take for example this .sources file from Cursor:

   ### THIS FILE IS AUTOMATICALLY CONFIGURED ###
   # You may comment out this entry, but any other modifications may be 
lost.
   Types: deb
   URIs: https://downloads.cursor.com/aptrepo
   Suites: stable
   Components: main
   Architectures: amd64,arm64
   Signed-By: /usr/share/keyrings/anysphere.gpg

We see that the two architectures are listed in a comma-separated 
fashion. However, sources.list(5) specifies that:

   Note especially that multiple values are separated  by  whitespaces
   (like spaces, tabs and newlines), not by commas as in the one-line
   format.

Meaning that the example above should be invalid and rejected by APT, 
but it was in fact allowed. Following this specification, oma was 
implemented in a way which it returns a warning and does not treat 
commas as separators:

     WARNING Mirror https://downloads.cursor.com/aptrepo does not 
contain architectures enabled in local configuration ('amd64' 'i386' 
enabled, 'amd64,arm64' available from the mirror)

Whereas APT accepts this source configuration just fine...

APT maintainers, would you please clarify on the usage of commas in 
DEB822 sources? It would be very helpful as we are currently not sure as 
to whether we should heed to the manpages or the de facto implementation 
currently found in APT.

Best Regards,
Mingcong Bai