Don't install dependencies of packages that can't be installed

[akimd (Akim Demaille)]

Hi!

$ sudo port install pdftk
Password:
--->  Computing dependencies for pdftk
The following dependencies will be installed: 
 gcc47
 glpk
 ppl
Continue? [Y/n]: 
--->  Fetching archive for glpk
--->  Attempting to fetch glpk-4.63_0.darwin_16.x86_64.tbz2 from http://lil.fr.packages.macports.org/glpk
--->  Attempting to fetch glpk-4.63_0.darwin_16.x86_64.tbz2.rmd160 from http://lil.fr.packages.macports.org/glpk
--->  Installing glpk @4.63_0
--->  Activating glpk @4.63_0
--->  Cleaning glpk
--->  Fetching archive for ppl
--->  Attempting to fetch ppl-1.2_0.darwin_16.x86_64.tbz2 from http://lil.fr.packages.macports.org/ppl
--->  Attempting to fetch ppl-1.2_0.darwin_16.x86_64.tbz2.rmd160 from http://lil.fr.packages.macports.org/ppl
--->  Installing ppl @1.2_0
--->  Activating ppl @1.2_0
--->  Cleaning ppl
--->  Fetching archive for gcc47
--->  Attempting to fetch gcc47-4.7.4_8.darwin_16.x86_64.tbz2 from http://lil.fr.packages.macports.org/gcc47
--->  Attempting to fetch gcc47-4.7.4_8.darwin_16.x86_64.tbz2.rmd160 from http://lil.fr.packages.macports.org/gcc47
--->  Installing gcc47 @4.7.4_8
--->  Activating gcc47 @4.7.4_8
--->  Cleaning gcc47
--->  Fetching archive for pdftk
--->  Attempting to fetch pdftk-2.02_0+gcc47.darwin_16.x86_64.tbz2 from http://lil.fr.packages.macports.org/pdftk
--->  Attempting to fetch pdftk-2.02_0+gcc47.darwin_16.x86_64.tbz2 from http://mse.uk.packages.macports.org/sites/packages.macports.org/pdftk
--->  Attempting to fetch pdftk-2.02_0+gcc47.darwin_16.x86_64.tbz2 from https://packages.macports.org/pdftk
--->  Fetching distfiles for pdftk
Error: pdftk currently does not build on OS X 10.11 or greater.
Error: See https://trac.macports.org/ticket/48528
Error: Failed to fetch pdftk: incompatible OS X version
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_textproc_pdftk/pdftk/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
Error: Processing of port pdftk failed

Now I have to uninstall these dependencies.

[ryandesign (Ryan Carsten Schmidt)]

Yes that would be nice. I'd love for there to be a new subcommand I could run, e.g. port installable pdftk, which could tell you in advance if a port is expected to be installable on the current system or not. And MacPorts could use that same hypothetical capability internally as you suggest, to prevent installing dependencies for non-installable ports.

But I don't know how we would accomplish that in base right now. The pdftk port has a pre-fetch block where the determination is made whether to attempt the install or bail. By the time that base is evaluating the pre-fetch block, dependencies have already been computed and installed. The introduction of a new phase, run before dependencies are computed, which ports could override with such checks, could be a possible solution.

We've talked about this problem before. I think someome mentioned that solving this problem will be easier once we have a new dependency resolution engine.

[mojca (Mojca Miklavec)]

I assume that fixing #15712 would take care of this.

[jmroot (Joshua Root)]

[d863a7e471d1afb4e405f5c5fbae470e26486a84/macports-base] and [3406c5d95e90c6624511a7fd9fee4d88a9d8896c/macports-base] should cover this.