Use Project-URL metadata field to get a PyPI package's homepage URL (#33089)

Resolves #33085.

routers/api/packages/pypi/pypi.go

@@ -10,6 +10,7 @@ import (
 	"regexp"
 	"sort"
 	"strings"
+	"unicode"
 
 	packages_model "code.gitea.io/gitea/models/packages"
 	packages_module "code.gitea.io/gitea/modules/packages"
@@ -139,9 +140,30 @@ func UploadPackageFile(ctx *context.Context) {
 		return
 	}
 
-	projectURL := ctx.Req.FormValue("home_page")
-	if !validation.IsValidURL(projectURL) {
-		projectURL = ""
+	// Ensure ctx.Req.Form exists.
+	_ = ctx.Req.ParseForm()
+
+	var homepageURL string
+	projectURLs := ctx.Req.Form["project_urls"]
+	for _, purl := range projectURLs {
+		label, url, found := strings.Cut(purl, ",")
+		if !found {
+			continue
+		}
+		if normalizeLabel(label) != "homepage" {
+			continue
+		}
+		homepageURL = strings.TrimSpace(url)
+		break
+	}
+
+	if len(homepageURL) == 0 {
+		// TODO: Home-page is a deprecated metadata field. Remove this branch once it's no longer apart of the spec.
+		homepageURL = ctx.Req.FormValue("home_page")
+	}
+
+	if !validation.IsValidURL(homepageURL) {
+		homepageURL = ""
 	}
 
 	_, _, err = packages_service.CreatePackageOrAddFileToExisting(
@@ -160,7 +182,7 @@ func UploadPackageFile(ctx *context.Context) {
 				Description:     ctx.Req.FormValue("description"),
 				LongDescription: ctx.Req.FormValue("long_description"),
 				Summary:         ctx.Req.FormValue("summary"),
-				ProjectURL:      projectURL,
+				ProjectURL:      homepageURL,
 				License:         ctx.Req.FormValue("license"),
 				RequiresPython:  ctx.Req.FormValue("requires_python"),
 			},
@@ -189,6 +211,23 @@ func UploadPackageFile(ctx *context.Context) {
 	ctx.Status(http.StatusCreated)
 }
 
+// Normalizes a Project-URL label.
+// See https://packaging.python.org/en/latest/specifications/well-known-project-urls/#label-normalization.
+func normalizeLabel(label string) string {
+	var builder strings.Builder
+
+	// "A label is normalized by deleting all ASCII punctuation and whitespace, and then converting the result
+	// to lowercase."
+	for _, r := range label {
+		if unicode.IsPunct(r) || unicode.IsSpace(r) {
+			continue
+		}
+		builder.WriteRune(unicode.ToLower(r))
+	}
+
+	return builder.String()
+}
+
 func isValidNameAndVersion(packageName, packageVersion string) bool {
 	return nameMatcher.MatchString(packageName) && versionMatcher.MatchString(packageVersion)
 }