Tell mesh-config what a head declares at every head, so a head that reverts a key drops its held value (issue 1826)

cmd/mesh-controller/pull_declares.go

@@ -68,12 +68,11 @@ func pullKey(owner, repo string, number int) string {
 func (p pullAt) key() string { return pullKey(p.Owner, p.Repo, p.Number) }
 
 // pullDeclarations are the config declarations a pull request's head adds or changes over what it merges into, by
-// module, in the shape of the declared-config mirror. The bool says the pull request changes a module.json that exists
-// at its head: mesh-config is told then, even of no declaration, so what it kept for an earlier head is replaced. A
-// pull request whose paths are truncated is read through the manifests of the modules it moves (the caller's paths).
+// module, in the shape of the declared-config mirror. The bool says the head could be read: false for a pull request whose
+// paths are cut (the caller cuts them to the manifests of the modules it moves) or whose base is unknown, which is then
+// told nothing, never an empty set.
 func pullDeclarations(ctx context.Context, p pullAt) ([]inventory.DeclaredConfigMirrored, bool, error) {
 	var out []inventory.DeclaredConfigMirrored
-	touched := false
 	if p.Truncated || p.Old == "" {
 		return nil, false, nil
 	}
@@ -88,7 +87,6 @@ func pullDeclarations(ctx context.Context, p pullAt) ([]inventory.DeclaredConfig
 		if !exists || now.Module == "" {
 			continue
 		}
-		touched = true
 		was, _, err := manifestCached(ctx, p.Owner, p.Repo, file, p.Old)
 		if err != nil {
 			return nil, false, err
@@ -111,19 +109,21 @@ func pullDeclarations(ctx context.Context, p pullAt) ([]inventory.DeclaredConfig
 			out = append(out, inventory.DeclaredConfigMirrored{Module: now.Module, Settings: changed})
 		}
 	}
-	return out, touched, nil
+	return out, true, nil
 }
 
-// tellPullDeclares tells mesh-config, for each pull request that changes a module.json, what its head declares. A
+// tellPullDeclares tells mesh-config, for each pull request at every announced head, what the head declares, an empty set
+// when it declares nothing new: mesh-config re-judges the values held at every head, so a head that reverts the change
+// drops them (ADR 0502 clause 6). A
 // failure is said to w and the check goes on: the held values are then none (ADR 0502 clause 2).
 func tellPullDeclares(ctx context.Context, w io.Writer, pulls []pullAt) {
 	for _, p := range pulls {
-		mods, touched, err := pullDeclarations(ctx, p)
+		mods, readable, err := pullDeclarations(ctx, p)
 		if err != nil {
 			fmt.Fprintf(w, "%s: what its head declares cannot be read, so mesh-config is told nothing: %v\n", p.key(), err)
 			continue
 		}
-		if !touched {
+		if !readable {
 			continue
 		}
 		declares := map[string]map[string]inventory.DeclaredMirrored{}
@@ -191,7 +191,21 @@ func heldFor(ctx context.Context, w io.Writer, pulls []pullAt) []link.HeldConfig
 // declarations are told.
 func withHeldConfig(ctx context.Context, w io.Writer, request *link.BuildRequest, pulls []pullAt, carry bool) {
 	tellPullDeclares(ctx, w, pulls)
-	if carry && request.Check != nil {
+	if carry {
+		carryHeld(ctx, w, request, pulls)
+	}
+}
+
+// carryHeld puts the approved held values of these pull requests on the check request.
+func carryHeld(ctx context.Context, w io.Writer, request *link.BuildRequest, pulls []pullAt) {
+	if request.Check != nil {
 		request.Check.HeldConfig = heldFor(ctx, w, pulls)
 	}
 }
+
+// holdsModules is whether a module of the mesh is built from this repository.
+func holdsModules(entries []inventory.Entry, owner, repo string) bool {
+	return slices.ContainsFunc(entries, func(e inventory.Entry) bool {
+		return sameRepository(e.Source.Repository, link.SourceMoved{Owner: owner, Repo: repo})
+	})
+}