[#839] service/object: Add high level functions to control request forwarding

Applicable for object/get execution context.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/services/object/get/assemble.go

@@ -12,11 +12,10 @@ func (exec *execCtx) assemble() {
 		return
 	}
 
-	// do not use forwarding during assembly stage
-	// assembly flag is not inherited in produced
-	// `execCtx`, however `commonPrm` does, so it
-	// makes sense to nil it there
-	exec.prm.SetRequestForwarder(nil)
+	// Do not use forwarding during assembly stage.
+	// Request forwarding closure inherited in produced
+	// `execCtx` so it should be disabled there.
+	exec.disableForwarding()
 
 	exec.log.Debug("trying to assemble the object...")
 

pkg/services/object/get/exec.go

@@ -347,3 +347,15 @@ func (exec *execCtx) writeCollectedObject() {
 		exec.writeObjectPayload(exec.collectedObject)
 	}
 }
+
+// isForwardingEnabled returns true if common execution
+// parameters has request forwarding closure set.
+func (exec execCtx) isForwardingEnabled() bool {
+	return exec.prm.forwarder != nil
+}
+
+// disableForwarding removes request forwarding closure from common
+// parameters, so it won't be inherited in new execution contexts.
+func (exec *execCtx) disableForwarding() {
+	exec.prm.SetRequestForwarder(nil)
+}

pkg/services/object/get/util.go

@@ -82,7 +82,7 @@ func (c *clientCacheWrapper) get(addr network.AddressGroup) (getClient, error) {
 }
 
 func (c *clientWrapper) getObject(exec *execCtx, addr network.AddressGroup) (*objectSDK.Object, error) {
-	if exec.prm.forwarder != nil {
+	if exec.isForwardingEnabled() {
 		return exec.prm.forwarder(addr, c.client)
 	}