librsvg @2.42.2 +universal: dependency cargo does not build universal

[ryandesign (Ryan Carsten Schmidt)]

$ port -v installed librsvg
The following ports are currently installed:
  librsvg @2.40.20_0+universal+viewer (active) platform='darwin 16' archs='i386 x86_64' date='2017-12-18T23:00:05-0600'
$ sudo port -u upgrade librsvg
--->  Computing dependencies for librsvg
Error: Cannot install librsvg for the archs 'i386 x86_64' because
Error: its dependency cargo does not build for the required archs by default
Error: and does not have a universal variant.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
$ 

Would it be sufficient to mark cargo and rust installs_libs no? Or do they actually install libraries that get embedded into things that are built with cargo or rust?

[dbevans (David B. Evans)]

In 6116c4d9ee73918f0e110db364bad0253753cbb2/macports-ports:

librsvg: disable +universal

Cargo does not build +universal. Disable until this is resolved.

Closes #55783

[ryandesign (Ryan Carsten Schmidt)]

But is it really necessary to disable librsvg's universal variant? The description of cargo says it "downloads your Rust project’s dependencies and compiles your project". That doesn't sound like it provides any libraries, so librsvg shouldn't care what its architecture is. Is adding installs_libs no to cargo appropriate?

[dbevans (David B. Evans)]

In 8df524236d94170f43d70f1c7b039706525a0326/macports-ports:

librsvg: conditionally revert to non-cargo version

Revert if cargo doesn't build, (+universal or 10.7 or earlier).
Unblocks dependents of librsvg where cargo is unavailable.

See #55783

[dbevans (David B. Evans)]

Hopefully, this will be less painful until the issues with cargo are worked out. I note that cargo's developers say it will run on 10.7 and up but the bootstrap fails on 10.7. Possibly not fetching a 10.7 compatible bootstrap version?

[ryandesign (Ryan Carsten Schmidt)]

Really fixed in [bcd0bba54c18b9c504e185d9f3e168b1bb54e5b7/macports-ports] using muniversal portgroup.