[#474] morph/client: Add FaultException to error msg

If non-"HALT" `State` occurs after
calling `InvokeFunction` NeoGo client
method, add `FaultException` information
to returning error. Add returning state
check to `NotaryInvoke` method of the
morph/client.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/morph/client/client.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"context"
+	"fmt"
 	"time"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/native/noderoles"
@@ -48,6 +49,18 @@ var ErrNilClient = errors.New("client is nil")
 // HaltState returned if TestInvoke function processed without panic.
 const HaltState = "HALT"
 
+type NotHaltStateError struct {
+	state, exception string
+}
+
+func (e *NotHaltStateError) Error() string {
+	return fmt.Sprintf(
+		"chain/client: contract execution finished with state %s; exception: %s",
+		e.state,
+		e.exception,
+	)
+}
+
 var errEmptyInvocationScript = errors.New("got empty invocation script from neo node")
 
 var errScriptDecode = errors.New("could not decode invocation script from neo node")
@@ -132,7 +145,7 @@ func (c *Client) TestInvoke(contract util.Uint160, method string, args ...interf
 	}
 
 	if val.State != HaltState {
-		return nil, errors.Errorf("chain/client: contract execution finished with state %s", val.State)
+		return nil, &NotHaltStateError{state: val.State, exception: val.FaultException}
 	}
 
 	return val.Stack, nil

pkg/morph/client/notary.go

@@ -222,6 +222,11 @@ func (c *Client) notaryInvoke(committee bool, contract util.Uint160, method stri
 		return err
 	}
 
+	// check invocation state
+	if test.State != HaltState {
+		return &NotHaltStateError{state: test.State, exception: test.FaultException}
+	}
+
 	// if test invocation failed, then return error
 	if len(test.Script) == 0 {
 		return errEmptyInvocationScript