Add format.GomegaString() to allow custom formatting of objects for t…

…ests only

format/format.go

@@ -53,6 +53,13 @@ var Indent = "    "
 
 var longFormThreshold = 20
 
+// GomegaStringer allows for custom formating of objects for gomega.
+type GomegaStringer interface {
+	// GomegaString will be used to custom format an object.
+	// It does not follow UseStringerRepresentation value and will always be called regardless.
+	GomegaString() string
+}
+
 /*
 Generates a formatted matcher success/failure message of the form:
 
@@ -219,9 +226,14 @@ func formatValue(value reflect.Value, indentation uint) string {
 		return "nil"
 	}
 
-	if UseStringerRepresentation {
-		if value.CanInterface() {
-			obj := value.Interface()
+	// GomegaStringer will take precedence to other representations and disregards UseStringerRepresentation
+	if value.CanInterface() {
+		obj := value.Interface()
+		if x, ok := obj.(GomegaStringer); ok {
+			return x.GomegaString()
+		}
+
+		if UseStringerRepresentation {
 			switch x := obj.(type) {
 			case fmt.GoStringer:
 				return x.GoString()

format/format_test.go

@@ -74,6 +74,13 @@ func (g Stringer) String() string {
 	return "string"
 }
 
+type gomegaStringer struct {
+}
+
+func (g gomegaStringer) GomegaString() string {
+	return "gomegastring"
+}
+
 var _ = Describe("Format", func() {
 	match := func(typeRepresentation string, valueRepresentation string, args ...interface{}) types.GomegaMatcher {
 		if len(args) > 0 {
@@ -654,6 +661,14 @@ var _ = Describe("Format", func() {
 				Expect(Object(Stringer{}, 1)).Should(ContainSubstring("<format_test.Stringer>: string"))
 			})
 		})
+
+		When("passed a GomegaStringer", func() {
+			It("should use what GomegaString() returns", func() {
+				Expect(Object(gomegaStringer{}, 1)).Should(ContainSubstring("<format_test.gomegaStringer>: gomegastring"))
+				UseStringerRepresentation = false
+				Expect(Object(gomegaStringer{}, 1)).Should(ContainSubstring("<format_test.gomegaStringer>: gomegastring"))
+			})
+		})
 	})
 
 	Describe("Printing a context.Context field", func() {