"git" with "build" modifier does not remember build failures

[fsoikin]

Description

When Paket pulls a git repo, runs build: script on it, and the build fails, Paket will report the error, but the next time Paket runs, it will not re-fetch or re-build the dependency in question, leaving it forever in the unbuilt state.

Some background I was trying to build Ionide, which has FsAutoComplete as one of dependencies, and it failed to build for me (see https://github.com/fsharp/FsAutoComplete/issues/184). But I didn't know at the time what the problem was, so from my point of view the experience was the following:

• I run Ionide's build.cmd.
• During dependency resolution, I get an error "FsAutoComplete blah-blah-blah failed to build".
• I run Ionide's build.cmd again.
• This time, it goes through and builds everything.
• I chalk it up to some intermittent issue, disregard it, and proceed with my tinkering.
• When executed, Ionide complains that it cannot start the language service.
• After some debugging, I find out that FsAutoComplete.Suave.exe is missing.
• After some more debugging, I figure out where it was supposed to come from, and realize that FsAutoComplete failed to build.

Repro steps

Please provide the steps required to reproduce the problem

1. Set up a git repo with a broken build script in it.
2. Add that repo to paket.dependencies with a build: modifier.
3. Run paket install, get a build error.
4. Run paket install again, get a successful result.

Expected behavior

Paket should somehow remember the failed build and attempt to rebuild on next restore/install.

Known workarounds

Manually build the failed dependencies.

[enricosada]

i can repro in FSAC or ionide too 😭