Allow user to specify the full name of the interface

[rakyll]

goimports cannot determine which namespace you would like to import
from. Given the following command,

$ impl 'c* Conn' driver.Conn

it implements the sql/driver.Conn interface even though I would like
to implement golang.org/x/exp/io/spi/driver.Conn.

This CL allows users to specify the namespace to remove ambiguity.

$ impl 'c *Conn' golang.org/x/exp/io/spi/driver.Conn
func (c *Conn) Configure(k int, v int) error {
  panic("not implemented")
}

func (c *Conn) Transfer(tx []byte, rx []byte) error {
  panic("not implemented")
}

func (c *Conn) Close() error {
  panic("not implemented")
}

[josharian]

Thanks! I have a few nits about the implementation while I'll leave as inline comments momentarily. Also, I believe that this will fix #7.

[josharian]

Since all we care about is the final /, if present, I think we can do this more cheaply and simply with strings.LastIndex and some string slicing.

[josharian]

Those are all my comments. Again, thanks!

[josharian]

Also: I'm super excited about x/exp/io. Any chance there'll be native OS X support for i2c, spi, etc. via the built-in OS X FTDI USB driver? That would have made this morning about 10x nicer. 😺 (Python+libmpsse+libftdi=ugh pain on so many levels.)

[dmitshur]

I have a comment too.

$ impl 'c *Conn' golang.org/x/exp/io/spi/driver.Conn

I've also had a need to be able to provide an exact import path and identifier to a CLI tool. I took inspiration from gorename which solved this problem before me. However, gorename needed to support more additional ways to specify identifiers, so I simplified its syntax to just a single case. See:

https://github.com/golang/tools/blob/9ae4729fba20b3533d829a9c6ba8195b068f2abc/refactor/rename/rename.go#L59

It looks like this:

"import/path".VariableName

It can be parsed as a Go expression:

https://github.com/shurcooL/vfsgen/blob/d61b62f6a1aa40a19aa6ae98c5ca0975b090ab27/cmd/vfsgendev/parse.go#L22-L55

My suggestion is to consider using that syntax so it's more similar to gorename and other tools.

[josharian]

gorename needs the quotes because it needs to be able to refer to things like methods with pointer receivers. This doesn't; interfaces always have simple names. And typing the quotes on the command line is annoying, because of the required escaping. So I'm happy with the UX for this PR.

[josharian]

I'd be OK with also accepting the quoted syntax, so that people and tools don't need to adapt specially to impl. But I'll also happily merge this PR without that; it can happen separately (and by you, if you are so inclined).

That reminds me, @jbd, a README update with this PR would be lovely.

[josharian]

Sorry, whoever I just paged, I meant @rakyll.

[rakyll]

All done, if you would like to add quote support, please do it after this CL is merged.

[josharian]

Thanks, @rakyll! I still have a few small nits, but rather than delaying for another back and forth, I'm going to merge this and then tweak a few things. Thanks, again.

[rakyll]

Thanks :)