Test unexported field access in format logic (#41)

The format logic should work even if the reflect.Value is in RO mode.

2 files changed, 6 insertions, 8 deletions

diff --git a/cmp/internal/value/format.go b/cmp/internal/value/format.go
index abaeca8..9b27152 100644
--- a/cmp/internal/value/format.go
+++ b/cmp/internal/value/format.go
@@ -13,10 +13,6 @@ import (
 	"unicode/utf8"
 )
 
-// formatFakePointers controls whether to substitute pointer addresses with nil.
-// This is used for deterministic testing.
-var formatFakePointers = false
-
 var stringerIface = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
 
 // Format formats the value v as a string.
@@ -27,7 +23,7 @@ var stringerIface = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
 //	* Prints a nil-slice as being nil, not empty
 //	* Prints map entries in deterministic order
 func Format(v reflect.Value, useStringer bool) string {
-	return formatAny(v, formatConfig{useStringer, true, true, !formatFakePointers}, nil)
+	return formatAny(v, formatConfig{useStringer, true, true, true}, nil)
 }
 
 type formatConfig struct {
diff --git a/cmp/internal/value/format_test.go b/cmp/internal/value/format_test.go
index 6498854..b56380f 100644
--- a/cmp/internal/value/format_test.go
+++ b/cmp/internal/value/format_test.go
@@ -80,10 +80,12 @@ func TestFormat(t *testing.T) {
 		want: "[2]interface {}{&[2]interface {}{(*[2]interface {})(0x00), interface {}(nil)}, interface {}(nil)}",
 	}}
 
-	formatFakePointers = true
-	defer func() { formatFakePointers = false }()
 	for i, tt := range tests {
-		got := Format(reflect.ValueOf(tt.in), true)
+		// Intentionally retrieve the value through an unexported field to
+		// ensure the format logic does not depend on read-write access
+		// to the reflect.Value.
+		v := reflect.ValueOf(struct{ x interface{} }{tt.in}).Field(0)
+		got := formatAny(v, formatConfig{useStringer: true, printType: true, followPointers: true}, nil)
 		if got != tt.want {
 			t.Errorf("test %d, Format():\ngot  %q\nwant %q", i, got, tt.want)
 		}