Feature mod aliases

docs/content/configuration/download.md

@@ -41,6 +41,10 @@ download "github.com/pkg/*" {
     mode = "redirect"
     downloadURL = "https://gocenter.io"
 }
+
+alias "github.com/gomods/athens-proxy" {
+    sourceURL = "github.com/gomods/athens"
+}
 ```
 
 The first two lines describe the behavior and the destination of all packages: redirect to `https://proxy.golang.org` and asynchronously persist the module to storage. 

download.example.hcl

@@ -14,3 +14,7 @@ download "github.com/pkg/*" {
     mode = "redirect"
     downloadURL = "https://gocenter.io"
 }
+
+alias "github.com/gomods/athens-proxy" {
+    sourceURL = "github.com/gomods/athens"
+}

pkg/download/latest.go

@@ -24,6 +24,8 @@ func LatestHandler(dp Protocol, lggr log.Entry, df *mode.DownloadFile) http.Hand
 			return
 		}
 
+		mod = df.Alias(mod)
+
 		info, err := dp.Latest(r.Context(), mod)
 		if err != nil {
 			severityLevel := errors.Expect(err, errors.KindNotFound)

pkg/download/list.go

@@ -25,6 +25,8 @@ func ListHandler(dp Protocol, lggr log.Entry, df *mode.DownloadFile) http.Handle
 			return
 		}
 
+		mod = df.Alias(mod)
+
 		versions, err := dp.List(r.Context(), mod)
 		if err != nil {
 			severityLevel := errors.Expect(err, errors.KindNotFound)

pkg/download/mode/mode.go

@@ -34,6 +34,7 @@ type DownloadFile struct {
 	Mode        Mode            `hcl:"mode"`
 	DownloadURL string          `hcl:"downloadURL"`
 	Paths       []*DownloadPath `hcl:"download,block"`
+	Aliases     []*ModAlias     `hcl:"alias,block"`
 }
 
 // DownloadPath represents a custom Mode for
@@ -44,6 +45,13 @@ type DownloadPath struct {
 	DownloadURL string `hcl:"downloadURL,optional"`
 }
 
+// ModAlias represents a custom source URL for
+// a module name.
+type ModAlias struct {
+	Name      string `hcl:"name,label"`
+	SourceURL string `hcl:"sourceURL"`
+}
+
 // NewFile takes a mode and returns a DownloadFile.
 // Mode can be one of the constants declared above
 // or a custom HCL file. To pass a custom HCL file,
@@ -125,6 +133,20 @@ func (d *DownloadFile) Match(mod string) Mode {
 	return d.Mode
 }
 
+// Alias returns the SourceURL that matches the given
+// module. A name is prioritized by order in
+// which it appears in the HCL file, while the
+// original URL will be returned if no aliases
+// exist.
+func (d *DownloadFile) Alias(mod string) string {
+	for _, p := range d.Aliases {
+		if p.Name == mod {
+			return p.SourceURL
+		}
+	}
+	return mod
+}
+
 // URL returns the redirect URL that applies
 // to the given module. If no pattern matches,
 // the top level downloadURL is returned.

pkg/download/mode/mode_test.go

@@ -6,11 +6,12 @@ import (
 )
 
 var testCases = []struct {
-	name         string
-	file         *DownloadFile
-	input        string
-	expectedMode Mode
-	expectedURL  string
+	name              string
+	file              *DownloadFile
+	input             string
+	expectedMode      Mode
+	expectedURL       string
+	expectedSourceURL string
 }{
 	{
 		name:         "sync",
@@ -101,6 +102,18 @@ var testCases = []struct {
 		expectedMode: Redirect,
 		expectedURL:  "proxy.golang.org",
 	},
+	{
+		name: "alias",
+		file: &DownloadFile{
+			Mode: Sync,
+			Aliases: []*ModAlias{
+				{Name: "github.com/gomods/athens-proxy", SourceURL: "github.com/gomods/athens"},
+			},
+		},
+		input:             "github.com/gomods/athens-proxy",
+		expectedSourceURL: "github.com/gomods/athens",
+		expectedMode:      Sync,
+	},
 }
 
 func TestMode(t *testing.T) {
@@ -114,6 +127,12 @@ func TestMode(t *testing.T) {
 			if givenURL != tc.expectedURL {
 				t.Fatalf("expected matched DownloadURL to be %q but got %q", tc.expectedURL, givenURL)
 			}
+			if tc.expectedSourceURL != "" {
+				givenSourceURL := tc.file.Alias(tc.input)
+				if givenSourceURL != tc.expectedSourceURL {
+					t.Fatalf("expected matched source url to be %q but got %q", tc.expectedSourceURL, givenSourceURL)
+				}
+			}
 		})
 	}
 }

pkg/download/version_info.go

@@ -21,6 +21,9 @@ func InfoHandler(dp Protocol, lggr log.Entry, df *mode.DownloadFile) http.Handle
 			w.WriteHeader(errors.Kind(err))
 			return
 		}
+
+		mod = df.Alias(mod)
+
 		info, err := dp.Info(r.Context(), mod, ver)
 		if err != nil {
 			severityLevel := errors.Expect(err, errors.KindNotFound, errors.KindRedirect)

pkg/download/version_module.go

@@ -22,6 +22,9 @@ func ModuleHandler(dp Protocol, lggr log.Entry, df *mode.DownloadFile) http.Hand
 			w.WriteHeader(errors.Kind(err))
 			return
 		}
+
+		mod = df.Alias(mod)
+
 		modBts, err := dp.GoMod(r.Context(), mod, ver)
 		if err != nil {
 			severityLevel := errors.Expect(err, errors.KindNotFound, errors.KindRedirect)

pkg/download/version_zip.go

@@ -22,6 +22,9 @@ func ZipHandler(dp Protocol, lggr log.Entry, df *mode.DownloadFile) http.Handler
 			w.WriteHeader(errors.Kind(err))
 			return
 		}
+
+		mod = df.Alias(mod)
+
 		zip, err := dp.Zip(r.Context(), mod, ver)
 		if err != nil {
 			severityLevel := errors.Expect(err, errors.KindNotFound, errors.KindRedirect)