feat(state): update dsl.State to support v3 params

- State struct will now accept params, and pass
in to StateHandler functions

See https://github.com/pact-foundation/pact-specification/tree/version-3#allow-multiple-provider-states-with-parameters

dsl/message.go

@@ -7,7 +7,7 @@ import (
 
 // StateHandler is a provider function that sets up a given state before
 // the provider interaction is validated
-type StateHandler func(string) error
+type StateHandler func(State) error
 
 // StateHandlers is a list of StateHandler's
 type StateHandlers map[string]StateHandler
@@ -52,12 +52,13 @@ type Message struct {
 // State specifies how the system should be configured when
 // verified. e.g. "user A exists"
 type State struct {
-	Name string `json:"name"`
+	Name   string                 `json:"name"`
+	Params map[string]interface{} `json:"params,omitempty"`
 }
 
 // Given specifies a provider state. Optional.
 func (p *Message) Given(state string) *Message {
-	p.States = []State{State{state}}
+	p.States = []State{State{Name: state}}
 
 	return p
 }

dsl/pact.go

@@ -356,7 +356,7 @@ var messageHandler = func(messageHandlers MessageHandlers, stateHandlers StateHa
 				log.Printf("[WARN] state handler not found for state: %v", state.Name)
 			} else {
 				// Execute state handler
-				if err = sf(state.Name); err != nil {
+				if err = sf(state); err != nil {
 					log.Printf("[WARN] state handler for '%v' return error: %v", state.Name, err)
 					w.WriteHeader(http.StatusInternalServerError)
 					return

examples/messages/provider/message_pact_provider_test.go

@@ -36,7 +36,7 @@ func TestMessageProvider_Success(t *testing.T) {
 	}
 
 	stateMappings := dsl.StateHandlers{
-		"user with id 127 exists": func(s string) error {
+		"user with id 127 exists": func(s dsl.State) error {
 			user = &types.User{
 				ID:   44,
 				Name: "Baz",
@@ -48,7 +48,7 @@ func TestMessageProvider_Success(t *testing.T) {
 
 			return nil
 		},
-		"no users": func(s string) error {
+		"no users": func(s dsl.State) error {
 			user = nil
 
 			return nil