Ask over mesh-sdk's composition: a question makes no pair credential and reads the mesh once (issue 1387)

The callers that only ask (status, the doctor's probes, facts, bindings, data, acts, nodes show, images, release, recorded push, consumers) resolve through resolveNode and compose through composeQuestion, over one Input read per operation (withInputCache). A question composes with Reading or Foreseeing and never calls PairCredential's maker: the credential a send would make is named, and perform makes it on a send.

cmd/mesh-controller/bindings.go

@@ -73,6 +73,8 @@ func reportKept(ctx context.Context, plan catalogue.Resolution) {
 // sent, on every machine — the resolver kept it there (said, urgent, until a person pins), or a pin
 // moves it (said, so the data goes first), and never anything else.
 func probeBindings(ctx context.Context, d *doctor) ([]conditions.Observation, error) {
+	// One reading of the mesh for every machine this looks at.
+	ctx = withInputCache(ctx)
 	inv := d.open.inventory
 	nodes, err := inv.Nodes(ctx)
 	if err != nil {
@@ -80,7 +82,7 @@ func probeBindings(ctx context.Context, d *doctor) ([]conditions.Observation, er
 	}
 	var out []conditions.Observation
 	for _, n := range nodes {
-		plan, _, err := planFor(ctx, d.open, n.Name)
+		plan, _, err := resolveNode(ctx, d.open, n.Name)
 		if err != nil {
 			if unresolvable(err) {
 				// D1 says it, with the binding that refused it when that is why.