Read only gitea's 404 status as not-found, so a 502 naming a sha with 404 in it is redelivered, not written backwards (issue 1126, review)

modules/mesh-delivery-indexer/internal/index/modules_test.go

@@ -207,6 +207,21 @@ func TestAnUnchangedModuleWritesNothing(t *testing.T) { // 1239 (unchanged value
 				}
 				return ix.Apply(context.Background(), mergedMsg(repo, three))
 			}},
+		// Review round 2: a 502 whose words carry "404" inside a sha is no not-found; the late message is left for redelivery.
+		{name: "a late message whose order the forge fails with a 502 writes nothing and is left for redelivery", writes: 1, commit: map[string]string{"a": next, "b": merge, "c": merge}, taken: next, err: true,
+			said: "502 Bad Gateway",
+			then: func(ix *Indexer) error {
+				ix.Contains = func(context.Context, string, string, string) (bool, error) { return false, nil }
+				later := mergedMsg(repo, map[string]string{"modules/a": "treeA2", "modules/b": "treeB", "modules/c": "treeC"})
+				later.Merge = next
+				if err := ix.Apply(context.Background(), later); err != nil {
+					return err
+				}
+				ix.Contains = func(context.Context, string, string, string) (bool, error) {
+					return false, errors.New("Gitea API /repos/x/y/compare/aaa404aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb: 502 Bad Gateway")
+				}
+				return ix.Apply(context.Background(), mergedMsg(repo, three))
+			}},
 		{name: "a forge that cannot say the order writes nothing and leaves the message for redelivery", writes: 0, commit: map[string]string{"a": merge}, taken: merge, err: true,
 			said: "cannot be read",
 			then: func(ix *Indexer) error {

modules/mesh-delivery-indexer/internal/index/order.go

@@ -40,8 +40,11 @@ func newMergeWrite(f delivery.Forge) *mergeWrite {
 	return &mergeWrite{repository: f.Repository, merge: f.Merge}
 }
 
-// notFound says the forge answered that a commit it was asked about does not exist (gitea's 404, as readVia reads it).
-func notFound(err error) bool { return err != nil && strings.Contains(err.Error(), "404") }
+// notFound says the forge answered that a commit it was asked about does not exist: gitea's status ": 404 ", matched as
+// readVia matches it (cmd/mesh-delivery-indexer named.go). A bare "404" is not enough: the error's words carry both shas,
+// and a 502 naming a sha with 404 in it would read as not older and write a late message backwards. The thorough form,
+// a typed not-found answered by gitea_contains, is noted on issue 1126.
+func notFound(err error) bool { return err != nil && strings.Contains(err.Error(), ": 404 ") }
 
 // older says commit is older than later: the forge says commit is in later and the two differ. A commit the forge does not
 // have is not known to be older (false, said); a forge that cannot say otherwise is an error. Without a forge to ask