go/build: Import seems to require absolute srcDir

[griesemer]

While investigating go/types issue #14215, I noticed that (after fixing the obvious go/types bug), build.Import didn't find the desired package if srcDir was relative. Computing its absolute path (relative to cwd) fixed the problem.

Reminder to investigate behavior. Fix and/or document.

[griesemer]

cc: @rsc

[griesemer]

If build.Import is changed/fixed such that it accepts a relative srcDir we can undo the changes to FindPkg (computing of absolute srcDir) in the following CLs:

http://golang.org/cl/19393
http://golang.org/cl/19394

[griesemer]

Another CL to update if this gets addressed: http://golang.org/cl/37405/

[griesemer]

@rsc I'm going to assign this one to you (go/build issue); to decide and/or fix or document since you're most familiar with go/build.

I can take care of my CLs that contain the work-arounds.

[griesemer]

If the solution turns out to be that build.Import creates an absolute path from a relative srcDir, build.Context may need to also export a new function field AbsPath func(path string) (string, error) (to match the other virtual file system support). By default (function is nil), filepath.Abs would be used instead. As is, libraries using a build.Context cannot handle the case correctly where srcDir is relative and build.Context provides customized file system functions because the libraries can't know how they should implement AbsPath. (see go/internal/srcimporter)