Allow mirror_urls in source.json

Context: bazelbuild/bazel-central-registry#4320

RELNTOES[NEW]: source.json now supports a new attribute `mirror_urls` as backup URLs for the source archive.

Closes bazelbuild#25928.

PiperOrigin-RevId: 750663220
Change-Id: I23ed94200ad555f7b1a756d76f3621fc0bd1b50f

Author: meteorcloudy

site/en/external/registry.md

@@ -83,6 +83,8 @@ field, which defaults to `archive`.
     by downloading an archive from a given URL and extracting its contents. It
     supports the following fields:
     *   `url`: A string, the URL of the source archive
+    *   `mirror_urls`: A list of string, the mirror URLs of the source archive.
+        The URLs are tried in order after `url` as backups.
     *   `integrity`: A string, the [Subresource
         Integrity][subresource-integrity] checksum of the archive
     *   `strip_prefix`: A string, the directory prefix to strip when extracting

src/main/java/com/google/devtools/build/lib/bazel/bzlmod/IndexRegistry.java

@@ -44,6 +44,7 @@
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URL;
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Optional;
@@ -259,6 +260,7 @@ private static class SourceJson {
   /** Represents fields in {@code source.json} for each archive-type version of a module. */
   private static class ArchiveSourceJson {
     URL url;
+    List<String> mirrorUrls;
     String integrity;
     String stripPrefix;
     Map<String, String> patches;
@@ -446,9 +448,14 @@ private RepoSpec createArchiveRepoSpec(
         urls.add(constructUrl(mirror, sourceUrl.getAuthority(), sourceUrl.getFile()));
       }
     }
-    // Finally add the original source URL itself.
+    // Add the original source URL itself.
     urls.add(sourceUrl.toString());
 
+    // Add mirror_urls from source.json as backups after the primary url.
+    if (sourceJson.mirrorUrls != null) {
+      urls.addAll(sourceJson.mirrorUrls);
+    }
+
     // Build remote patches as key-value pairs of "url" => "integrity".
     ImmutableMap.Builder<String, String> remotePatches = new ImmutableMap.Builder<>();
     if (sourceJson.patches != null) {

src/test/java/com/google/devtools/build/lib/bazel/bzlmod/IndexRegistryTest.java

@@ -182,6 +182,8 @@ public void testGetArchiveRepoSpec() throws Exception {
         "/modules/foo/1.0/source.json",
         "{",
         "  \"url\": \"http://mysite.com/thing.zip\",",
+        "  \"mirror_urls\":"
+            + " [\"http://my.mirror/mysite.com/thing.zip\",\"http://another.mirror/mysite.com/thing.zip\"],",
         "  \"integrity\": \"sha256-blah\",",
         "  \"strip_prefix\": \"pref\"",
         "}");
@@ -223,7 +225,9 @@ public void testGetArchiveRepoSpec() throws Exception {
                     ImmutableList.of(
                         "https://mirror.bazel.build/mysite.com/thing.zip",
                         "file:///home/bazel/mymirror/mysite.com/thing.zip",
-                        "http://mysite.com/thing.zip"))
+                        "http://mysite.com/thing.zip",
+                        "http://my.mirror/mysite.com/thing.zip",
+                        "http://another.mirror/mysite.com/thing.zip"))
                 .setIntegrity("sha256-blah")
                 .setStripPrefix("pref")
                 .setRemotePatches(ImmutableMap.of())