gddo-server: account for vendor dirs in pkg.go.dev redirect

Pkg.go.dev does not support documentation for vendor directories.
When showing the corresponding pkg.go.dev link in the header or
when automatically redirecting, change the destination to be the
pkg.go.dev homepage instead of a vendor link that will 404.

Fixes golang/go#38671

Change-Id: Ic7d221d3cc7fef352f5c7097a667fb8dd2ad0340
Reviewed-on: https://go-review.googlesource.com/c/gddo/+/233839
Run-TryBot: Andrew Bonventre <[email protected]>
Reviewed-by: Julie Qiu <[email protected]>

Author: andybons

gddo-server/assets/templates/importers.html

@@ -7,5 +7,5 @@ <h3>Packages that import {{$.pdoc.Name}}</h3>
 {{end}}
 
 {{define "PkgGoDevLink"}}
-  <a href="https://pkg.go.dev{{if .pdoc.ImportPath}}/{{.pdoc.ImportPath}}{{end}}?tab=importedby">pkg.go.dev{{if .pdoc.ImportPath}}/{{.pdoc.ImportPath}}?tab=importedby{{end}}</a>
+  <a href="https://pkg.go.dev{{if .pdoc.ImportPath}}{{if notVendorPath .pdoc.ImportPath}}/{{.pdoc.ImportPath}}?tab=importedby{{end}}{{end}}">pkg.go.dev{{if .pdoc.ImportPath}}{{if notVendorPath .pdoc.ImportPath}}/{{.pdoc.ImportPath}}?tab=importedby{{end}}{{end}}</a>
 {{end}}

gddo-server/assets/templates/imports.html

@@ -7,5 +7,5 @@ <h3>Packages imported by {{.pdoc.Name}}</h3>
 {{end}}
 
 {{define "PkgGoDevLink"}}
-  <a href="https://pkg.go.dev{{if .pdoc.ImportPath}}/{{.pdoc.ImportPath}}{{end}}?tab=imports">pkg.go.dev{{if .pdoc.ImportPath}}/{{.pdoc.ImportPath}}?tab=imports{{end}}</a>
+  <a href="https://pkg.go.dev{{if .pdoc.ImportPath}}{{if notVendorPath .pdoc.ImportPath}}/{{.pdoc.ImportPath}}?tab=imports{{end}}{{end}}">pkg.go.dev{{if .pdoc.ImportPath}}{{if notVendorPath .pdoc.ImportPath}}/{{.pdoc.ImportPath}}?tab=imports{{end}}{{end}}</a>
 {{end}}

gddo-server/main.go

@@ -1171,6 +1171,12 @@ func pkgGoDevURL(godocURL *url.URL) *url.URL {
 	u := &url.URL{Scheme: "https", Host: pkgGoDevHost}
 	q := url.Values{"utm_source": []string{"godoc"}}
 
+	if strings.Contains(godocURL.Path, "/vendor/") || strings.HasSuffix(godocURL.Path, "/vendor") {
+		u.Path = "/"
+		u.RawQuery = q.Encode()
+		return u
+	}
+
 	switch godocURL.Path {
 	case "/-/go":
 		u.Path = "/std"

gddo-server/main_test.go

@@ -151,6 +151,14 @@ func TestGodoc(t *testing.T) {
 			from: "https://godoc.org/cloud.google.com/go/storage?importers",
 			to:   "https://pkg.go.dev/cloud.google.com/go/storage?tab=importedby&utm_source=godoc",
 		},
+		{
+			from: "https://godoc.org/golang.org/x/vgo/vendor/cmd/go/internal/modfile",
+			to:   "https://pkg.go.dev/?utm_source=godoc",
+		},
+		{
+			from: "https://godoc.org/golang.org/x/vgo/vendor",
+			to:   "https://pkg.go.dev/?utm_source=godoc",
+		},
 	}
 
 	for _, tc := range testCases {

gddo-server/template.go

@@ -521,7 +521,7 @@ func joinTemplateDir(base string, files []string) []string {
 
 const pkgGoDevLinkTmpl = `
 {{define "PkgGoDevLink"}}
-  <a href="https://pkg.go.dev{{if .pdoc.ImportPath}}/{{.pdoc.ImportPath}}{{end}}">pkg.go.dev{{if .pdoc.ImportPath}}/{{.pdoc.ImportPath}}{{end}}</a>
+  <a href="https://pkg.go.dev{{if .pdoc.ImportPath}}{{if notVendorPath .pdoc.ImportPath}}/{{.pdoc.ImportPath}}{{end}}{{end}}">pkg.go.dev{{if .pdoc.ImportPath}}{{if notVendorPath .pdoc.ImportPath}}/{{.pdoc.ImportPath}}{{end}}{{end}}</a>
 {{end}}
 `
 
@@ -559,6 +559,7 @@ func parseTemplates(dir string, cb *httputil.CacheBusters, v *viper.Viper) (temp
 		"relativePath":      relativePathFn,
 		"sidebarEnabled":    func() bool { return v.GetBool(ConfigSidebar) },
 		"staticPath":        func(p string) string { return cb.AppendQueryParam(p, "v") },
+		"notVendorPath":     func(p string) bool { return !strings.Contains(p, "/vendor") },
 	}
 	for _, set := range htmlSets {
 		templateName := set[0]