internal/imports: only check first segment for .

An import path like "foo/bar.v1" is still a local path, not an external
package, and should be grouped as such.

Change-Id: I06be3c01076f616a3cdc8e23bc9c056643035ad1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/234111
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/imports/fix.go

@@ -50,7 +50,8 @@ var importToGroup = []func(env *ProcessEnv, importPath string) (num int, ok bool
 		return
 	},
 	func(_ *ProcessEnv, importPath string) (num int, ok bool) {
-		if strings.Contains(importPath, ".") {
+		firstComponent := strings.Split(importPath, "/")[0]
+		if strings.Contains(firstComponent, ".") {
 			return 1, true
 		}
 		return

internal/imports/fix_test.go

@@ -846,7 +846,6 @@ import (
 var _ = fmt.Sprintf
 `,
 	},
-
 	{
 		name: "import_grouping_not_path_dependent_no_groups",
 		in: `package main
@@ -2696,3 +2695,36 @@ func _() {
 		wg.Wait()
 	})
 }
+
+func TestNonlocalDot(t *testing.T) {
+	const input = `package main
+import (
+	"fmt"
+)
+var _, _ = fmt.Sprintf, dot.Dot
+`
+	const want = `package main
+
+import (
+	"fmt"
+	"noninternet/dot.v1/dot"
+)
+
+var _, _ = fmt.Sprintf, dot.Dot
+`
+	testConfig{
+		modules: []packagestest.Module{
+			{
+				Name:  "golang.org/fake",
+				Files: fm{"x.go": input},
+			},
+			{
+				Name: "noninternet/dot.v1",
+				Files: fm{
+					"dot/dot.go": "package dot\nfunc Dot(){}\n",
+				},
+			},
+		},
+		gopathOnly: true, // our modules testing setup doesn't allow modules without dots.
+	}.processTest(t, "golang.org/fake", "x.go", nil, nil, want)
+}