invoker: add Signers() API

Signers are very important for notary checks and keeping/passing an additional
copy of them is very inconvenient. Exposing them from invoker makes them
available in actors too.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

pkg/rpcclient/invoker/invoker.go

@@ -137,6 +137,20 @@ func (h *historicConverter) TraverseIterator(sessionID, iteratorID uuid.UUID, ma
 	return h.client.TraverseIterator(sessionID, iteratorID, maxItemsCount)
 }
 
+// Signers returns the set of current invoker signers which is mostly useful
+// when working with upper-layer actors. Returned slice is a newly allocated
+// one (if this invoker has them), so it's safe to modify.
+func (v *Invoker) Signers() []transaction.Signer {
+	if v.signers == nil {
+		return nil
+	}
+	var res = make([]transaction.Signer, len(v.signers))
+	for i := range v.signers {
+		res[i] = *v.signers[i].Copy()
+	}
+	return res
+}
+
 // Call invokes a method of the contract with the given parameters (and
 // Invoker-specific list of signers) and returns the result as is.
 func (v *Invoker) Call(contract util.Uint160, operation string, params ...any) (*result.Invoke, error) {

pkg/rpcclient/invoker/invoker_test.go

@@ -158,3 +158,19 @@ func TestInvoker(t *testing.T) {
 		}
 	})
 }
+
+func TestInvokerSigners(t *testing.T) {
+	resExp := &result.Invoke{State: "HALT"}
+	ri := &rpcInv{resExp, true, nil, nil}
+	inv := New(ri, nil)
+
+	require.Nil(t, inv.Signers())
+
+	s := []transaction.Signer{}
+	inv = New(ri, s)
+	require.Equal(t, s, inv.Signers())
+
+	s = append(s, transaction.Signer{Account: util.Uint160{1, 2, 3}, Scopes: transaction.CalledByEntry})
+	inv = New(ri, s)
+	require.Equal(t, s, inv.Signers())
+}