Merge pull request #136 from frankban/different-pointers-same-format

Improve failure output when comparing different pointers

checker.go

@@ -100,6 +100,7 @@ func (c *equalsChecker) Check(got interface{}, args []interface{}, note func(key
 			}
 		}
 	}
+
 	return errors.New("values are not equal")
 }
 

checker_test.go

@@ -265,7 +265,37 @@ want type:
 got:
   e"bad wolf"
 want:
-  <same as "got">
+  <same as "got" but different pointer value>
+`,
+}, {
+	about:   "Equals: different pointer errors with the same message",
+	checker: qt.Equals,
+	got: &errTest{
+		msg: "bad wolf",
+	},
+	args: []interface{}{&errTest{
+		msg: "bad wolf",
+	}},
+	expectedCheckFailure: `
+error:
+  values are not equal
+got:
+  e"bad wolf"
+want:
+  <same as "got" but different pointer value>
+`,
+}, {
+	about:   "Equals: different pointers with the same formatted output",
+	checker: qt.Equals,
+	got:     new(int),
+	args:    []interface{}{new(int)},
+	expectedCheckFailure: `
+error:
+  values are not equal
+got:
+  &int(0)
+want:
+  <same as "got" but different pointer value>
 `,
 }, {
 	about:   "Equals: nil struct",

report.go

@@ -51,6 +51,7 @@ func report(err error, p reportParams) string {
 // writeError writes a pretty formatted output of the given error using the
 // provided report parameters.
 func writeError(w io.Writer, err error, p reportParams) {
+	ptrs := make(map[string]interface{})
 	values := make(map[string]string)
 	printPair := func(key string, value interface{}) {
 		fmt.Fprintln(w, key+":")
@@ -60,10 +61,18 @@ func writeError(w io.Writer, err error, p reportParams) {
 		} else {
 			v = p.format(value)
 		}
+		isPtr := reflect.ValueOf(value).Kind() == reflect.Ptr
 		if k := values[v]; k != "" {
+			if previousValue, ok := ptrs[k]; ok && isPtr && previousValue != value {
+				fmt.Fprint(w, prefixf(prefix, "<same as %q but different pointer value>", k))
+				return
+			}
 			fmt.Fprint(w, prefixf(prefix, "<same as %q>", k))
 			return
 		}
+		if isPtr {
+			ptrs[key] = value
+		}
 		values[v] = key
 		fmt.Fprint(w, prefixf(prefix, "%s", v))
 	}