Allow to set build tags

[zimmski]

I now that this breaks the API but the usage is wrong without it if you support build tags in a tool, like in errcheck. I will send out a PR for this in a moment.

[dominikh]

In my opinion, changing the signature isn't really an option, especially because the new API doesn't look sane, having to carry tags through various functions, singling out a single of the buildContext fields.

The real issue is that the user cannot modify the build context. One option would be to allow access to the global build context, but that wouldn't be thread-safe. Another option might be to provide a new type (type Context struct or something like that), which has an ImportPaths(args []string) method and a BuildContext field.

It should be noted that this code is lifted directly from the Go tool. buildContext was an oversight. The Go tool itself does set tags by manipulating the global buildContext, which won't work for us.

[zimmski]

That would mean that most functions will be turned into methods of the new Context type. Also the old ImportPaths would then instantiate a Context. Is that OK?

[dominikh]

That sounds fine to me, but let's wait for @kisielk

[kisielk]

Okay, I had some time to look in to how the go tool works with regards to the build context. I agree we should just provide our own Context type that embeds build.Context and has an ImportPaths method. Then the package can instantiate the default in to a global DefaultContext.

[zimmski]

Sounds good. So it is also fine with you to convert the currently touched functions into methods?
On Aug 14, 2015 6:20 PM, Kamil Kisiel notifications@github.com wrote:Okay, I had some time to look in to how the go tool works with regards to the build context. I agree we should just provide our own Context type that embeds build.Context and has an ImportPaths method. Then the package can instantiate the default in to a global DefaultContext.

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[kisielk]

Yeah, the unexported functions can be made in to the methods on the new type. The exported ImportPaths function can just call DefaultContext.ImportPaths

[zimmski]

Done, please take another look.

[kisielk]

Looks good. Next step is to use gotool.Context in errcheck I guess.