Provide passive per-source resource contexts

internal/engine/resolution.go

@@ -72,6 +72,12 @@ func (r *Resolution) Source(id string) (SourceInfo, bool) {
 	return r.activeState().input.source(id)
 }
 
+// SourceContext returns a passive context during the active resolution
+// callback. Retaining the callback context after return is unsupported.
+func (r *Resolution) SourceContext(id string) (ResourceContext, bool) {
+	return r.activeState().input.sourceContext(id)
+}
+
 // Record declares the intent for a resolver mutation. A container path covers
 // mutations to its descendants.
 func (r *Resolution) Record(path Path, kind ChangeKind, reason string, dependencies ...Path) {