fix: print value type for interface{} containers (#409)

When a value is contained in an interface{} we should show the type of
the value as well as the interface{} type

Consider the test:

  Expect([]interface{}{1}).To(Equal([]interface{}{uint(1)}))

Previous message:

  Expected
    <[]interface {} | len:1, cap:1>: [1]
  to equal
    <[]interface {} | len:1, cap:1>: [1]

New message:

  Expected
    <[]interface {} | len:1, cap:1>: [<int>1]
  to equal
    <[]interface {} | len:1, cap:1>: [<uint>1]

By showing the type, it's much easier to work out what is going on

format/format.go

@@ -271,7 +271,7 @@ func formatValue(value reflect.Value, indentation uint) string {
 		}
 		return formatStruct(value, indentation)
 	case reflect.Interface:
-		return formatValue(value.Elem(), indentation)
+		return formatInterface(value, indentation)
 	default:
 		if value.CanInterface() {
 			return fmt.Sprintf("%#v", value.Interface())
@@ -366,6 +366,10 @@ func formatStruct(v reflect.Value, indentation uint) string {
 	return fmt.Sprintf("{%s}", strings.Join(result, ", "))
 }
 
+func formatInterface(v reflect.Value, indentation uint) string {
+	return fmt.Sprintf("<%s>%s", formatType(v.Elem()), formatValue(v.Elem(), indentation))
+}
+
 func isNilValue(a reflect.Value) bool {
 	switch a.Kind() {
 	case reflect.Invalid:

format/format_test.go

@@ -95,7 +95,7 @@ var _ = Describe("Format", func() {
 		for i := range arr {
 			arr[i] = entriesSwitch
 		}
-		return "{" + strings.Join(arr, ", ") + "}"
+		return "{\\s*" + strings.Join(arr, ",\\s* ") + ",?\\s*}"
 	}
 
 	Describe("Message", func() {
@@ -526,6 +526,24 @@ var _ = Describe("Format", func() {
 			})
 		})
 
+		Describe("formatting nested interface{} types", func() {
+			It("should print out the types of the container and value", func() {
+				Expect(Object([]interface{}{"foo"}, 1)).
+					To(match("[]interface {} | len:1, cap:1", `[<string>"foo"]`))
+
+				Expect(Object(map[string]interface{}{"foo": true}, 1)).
+					To(match("map[string]interface {} | len:1", `{"foo": <bool>true}`))
+
+				Expect(Object(struct{ A interface{} }{A: 1}, 1)).
+					To(match("struct { A interface {} }", "{A: <int>1}"))
+
+				v := struct{ A interface{} }{A: struct{ B string }{B: "foo"}}
+				Expect(Object(v, 1)).To(match(`struct { A interface {} }`, `{
+        A: <struct { B string }>{B: "foo"},
+    }`))
+			})
+		})
+
 		Describe("formatting times", func() {
 			It("should format time as RFC3339", func() {
 				t := time.Date(2016, 10, 31, 9, 57, 23, 12345, time.UTC)
@@ -574,7 +592,7 @@ var _ = Describe("Format", func() {
         byteArrValue: \[17, 20, 32\],
         mapValue: %s,
         structValue: {Exported: "exported"},
-        interfaceValue: {"a key": 17},
+        interfaceValue: <map\[string\]int \| len:1>{"a key": 17},
     }`, s.chanValue, s.funcValue, hashMatchingRegexp(`"a key": 20`, `"b key": 30`))
 
 			Expect(Object(s, 1)).Should(matchRegexp(`format_test\.SecretiveStruct`, expected))
@@ -590,7 +608,7 @@ var _ = Describe("Format", func() {
 			outerHash["integer"] = 2
 			outerHash["map"] = innerHash
 
-			expected := hashMatchingRegexp(`"integer": 2`, `"map": {"inner": 3}`)
+			expected := hashMatchingRegexp(`"integer": <int>2`, `"map": <map\[string\]int \| len:1>{"inner": 3}`)
 			Expect(Object(outerHash, 1)).Should(matchRegexp(`map\[string\]interface {} \| len:2`, expected))
 		})
 	})

matchers/consist_of_test.go

@@ -160,7 +160,7 @@ the extra elements were
 				})
 
 				expected := `to consist of
-\s*<\[\]interface {} \| len:2, cap:2>: \[1, "C"\]
+\s*<\[\]interface {} \| len:2, cap:2>: \[<int>1, <string>"C"\]
 the missing elements were
 \s*<\[\]string \| len:1, cap:1>: \["C"\]
 the extra elements were
@@ -173,7 +173,7 @@ the extra elements were
 					Expect([]interface{}{1, "B"}).NotTo(ConsistOf(1, "B"))
 				})
 
-				expected := `not to consist of\n\s*<\[\]interface {} \| len:2, cap:2>: \[1, "B"\]`
+				expected := `not to consist of\n\s*<\[\]interface {} \| len:2, cap:2>: \[<int>1, <string>"B"\]`
 				Expect(failures).To(ConsistOf(MatchRegexp(expected)))
 			})
 		})

matchers/contain_elements_matcher_test.go

@@ -133,7 +133,7 @@ the missing elements were
 				})
 
 				expected := `to contain elements
-\s*<\[\]interface {} \| len:2, cap:2>: \[1, "C"\]
+\s*<\[\]interface {} \| len:2, cap:2>: \[<int>1, <string>"C"\]
 the missing elements were
 \s*<\[\]string \| len:1, cap:1>: \["C"\]`
 				Expect(failures).To(ConsistOf(MatchRegexp(expected)))
@@ -144,7 +144,7 @@ the missing elements were
 					Expect([]interface{}{1, "B"}).NotTo(ContainElements(1, "B"))
 				})
 
-				expected := `not to contain elements\n\s*<\[\]interface {} \| len:2, cap:2>: \[1, "B"\]`
+				expected := `not to contain elements\n\s*<\[\]interface {} \| len:2, cap:2>: \[<int>1, <string>"B"\]`
 				Expect(failures).To(ConsistOf(MatchRegexp(expected)))
 			})
 		})