Resolve vanity URLs to proper import paths

This resolves imports like "rsc.io/pdf" to "github.com/rsc/pdf"

README.md

@@ -134,9 +134,3 @@ at any of these, please do and contribute!
 a GitHub project changes licenses. `golicense` uses the GitHub API which only
 returns the license currently detected; we can't lookup licenses for specific
 commit hashes.
-
-**Import Redirects:** Import paths that redirect to GitHub projects
-(such as `gonum.org/v1/gonum`) aren't properly translated currently. To fix
-this we should use the `go get` HTTP protocol to detect these and do the
-proper translation. For now, you can work around this using explicit overrides
-via a configuration file.

go.mod

@@ -34,6 +34,7 @@ require (
 	golang.org/x/crypto v0.0.0-20180904163835-0709b304e793
 	golang.org/x/exp v0.0.0-20181112044915-a3060d491354 // indirect
 	golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be
+	golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b
 	gonum.org/v1/gonum v0.0.0-20181115051416-e2f95e5c31f6 // indirect
 	gopkg.in/neurosnap/sentences.v1 v1.0.6 // indirect
 	gopkg.in/russross/blackfriday.v2 v2.0.0 // indirect

go.sum

@@ -124,6 +124,7 @@ golang.org/x/sys v0.0.0-20180903190138-2b024373dcd9 h1:lkiLiLBHGoH3XnqSLUIaBsilG
 golang.org/x/sys v0.0.0-20180903190138-2b024373dcd9/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b h1:7tibmaEqrQYA+q6ri7NQjuxqSwechjtDHKq6/e85S38=
 golang.org/x/tools v0.0.0-20180525024113-a5b4c53f6e8b/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gonum.org/v1/gonum v0.0.0-20181115051416-e2f95e5c31f6 h1:Sv4KG3MNOeKJKMiAP1fqkOfZQJoYhqGf+jgelT7jH2o=
 gonum.org/v1/gonum v0.0.0-20181115051416-e2f95e5c31f6/go.mod h1:Y+Yx5eoAFn32cQvJDxZx5Dpnq+c3wtXuadVZAcxbbBo=

license/golang/translator.go

@@ -24,4 +24,4 @@ func (t Translator) Translate(ctx context.Context, m module.Module) (module.Modu
 // re is the regexp matching the package for a GoPkg import. This is taken
 // almost directly from the GoPkg source code itself so it should match
 // perfectly.
-var re = regexp.MustCompile(`^golang\.org/x/([^/]+)$`)
+var re = regexp.MustCompile(`^go\.googlesource\.com/([^/]+)$`)

license/golang/translator_test.go

@@ -19,8 +19,8 @@ func TestTranslator(t *testing.T) {
 		},
 
 		{
-			"golang.org/x/crypto",
-			"github.com/golang/crypto",
+			"go.googlesource.com/text",
+			"github.com/golang/text",
 		},
 	}
 

license/resolver/translate.go

@@ -0,0 +1,35 @@
+package resolver
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+
+	"github.com/mitchellh/golicense/license"
+	"github.com/mitchellh/golicense/module"
+	"golang.org/x/tools/go/vcs"
+)
+
+// Translator resolves import paths to their proper VCS location. For
+// example: "rsc.io/pdf" turns into "github.com/rsc/pdf".
+type Translator struct{}
+
+func (t Translator) Translate(ctx context.Context, m module.Module) (module.Module, bool) {
+	root, err := vcs.RepoRootForImportPath(m.Path, false)
+	if err != nil {
+		return module.Module{}, false
+	}
+
+	path := hostStripRe.ReplaceAllString(root.Repo, "")
+	if m.Path == path {
+		return module.Module{}, false
+	}
+
+	license.UpdateStatus(ctx, license.StatusNormal, fmt.Sprintf(
+		"translated %q to %q", m.Path, path))
+	m.Path = path
+	return m, true
+}
+
+// hostStripRe is a simple regexp to strip the schema from a URL.
+var hostStripRe = regexp.MustCompile(`^\w+:\/\/`)

license/resolver/translate_test.go

@@ -0,0 +1,48 @@
+package resolver
+
+import (
+	"context"
+	"testing"
+
+	"github.com/mitchellh/golicense/module"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTranslator(t *testing.T) {
+	cases := []struct {
+		Input  string
+		Output string
+	}{
+		{
+			"github.com/foo/bar",
+			"",
+		},
+
+		{
+			"golang.org/x/text",
+			"go.googlesource.com/text",
+		},
+
+		{
+			"gonum.org/v1/gonum",
+			"github.com/gonum/gonum",
+		},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.Input, func(t *testing.T) {
+			var tr Translator
+			actual, ok := tr.Translate(context.Background(), module.Module{
+				Path: tt.Input,
+			})
+
+			if tt.Output == "" {
+				require.False(t, ok)
+				return
+			}
+
+			require.True(t, ok)
+			require.Equal(t, tt.Output, actual.Path)
+		})
+	}
+}

main.go

@@ -20,6 +20,7 @@ import (
 	"github.com/mitchellh/golicense/license/golang"
 	"github.com/mitchellh/golicense/license/gopkg"
 	"github.com/mitchellh/golicense/license/mapper"
+	"github.com/mitchellh/golicense/license/resolver"
 	"github.com/mitchellh/golicense/module"
 )
 
@@ -131,6 +132,7 @@ func realMain() int {
 	// Build our translators and license finders
 	ts := []license.Translator{
 		&mapper.Translator{Map: cfg.Translate},
+		&resolver.Translator{},
 		&golang.Translator{},
 		&gopkg.Translator{},
 	}