tree e0f755601c4ee21bd59f48caad0dd22e925a6180
parent 5831d16d18029819d39f99bdc2060b8eff410b6b
author haya14busa <haya14busa@gmail.com> 1488355364 +0900
committer Josh Bleecher Snyder <josharian@gmail.com> 1502757540 +0000

go/ast/astutil: new third-party imports shouldn't go in the std group

Before this change, astutil would only do a prefix match of a new import
with all the existing ones, to try to place it in the correct group. If
none was found, the new import would be placed at the beginning of the
first import group.

This works well for new std imports, but it doesn't work well for new
third-party packages that don't share any prefix with any of the
existing imports.

Example:

	import (
		"time"

		"github.com/golang/snappy"
	)

When adding "golang.org/x/sys/unix" with astutil.AddImport, the import
is inserted as follows:

	import (
		"golang.org/x/sys/unix"
		"time"

		"github.com/golang/snappy"
	)

And goimports reorganizes the imports to separate std and third-party
packages:

	import (
		"time"

		"golang.org/x/sys/unix"

		"github.com/golang/snappy"
	)

We usually don't want to introduce a new import group; in most cases,
the desired behavior is separating std from third-party packages.

With this CL, new imports that don't share prefix with any existing ones
will be placed with the first group of third-party imports, if any
exist. If no third-party import group exists, a new one will be added.
In the case of our example above, this will be the new outcome:

	import (
		"time"

		"github.com/golang/snappy"
		"golang.org/x/sys/unix"
	)

Fixes golang/go#19190.

Change-Id: Id4630015c029bd815234a6c8726cb97f4af16f1c
Reviewed-on: https://go-review.googlesource.com/37552
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>