Use github.com/kylelemons/godebug for assert diffs

go.mod

@@ -6,6 +6,7 @@ require (
 	cloud.google.com/go v0.43.0
 	github.com/alecthomas/chroma v0.6.6
 	github.com/fatih/color v1.7.0
+	github.com/kylelemons/godebug v1.1.0
 	github.com/mattn/go-colorable v0.1.2 // indirect
 	github.com/mattn/go-isatty v0.0.9 // indirect
 	go.opencensus.io v0.22.1

go.sum

@@ -64,6 +64,8 @@ github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
 github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/mattn/go-colorable v0.0.9 h1:UVL0vNpWh04HeJXV0KLcaT7r06gOH2l4OW6ddYRUIY4=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-colorable v0.1.2 h1:/bC9yWikZXAL9uJdulbSfyVNIR3n3trXl+v8+1sx8mU=

internal/assert/assert.go

@@ -4,13 +4,16 @@ package assert
 import (
 	"reflect"
 	"testing"
+
+	"github.com/kylelemons/godebug/pretty"
 )
 
 // Equal asserts exp == act.
 func Equal(t testing.TB, name string, exp, act interface{}) {
 	t.Helper()
 	if !reflect.DeepEqual(exp, act) {
-		t.Fatalf("unexpected %v: exp: %q but got %q", name, exp, act)
+		t.Fatalf(`unexpected %v: diff:
+%v`, name, pretty.Compare(exp, act))
 	}
 }
 

internal/entryhuman/entry.go

@@ -119,11 +119,20 @@ func Fmt(w io.Writer, ent slog.SinkEntry) string {
 	}
 
 	if multilineVal != "" {
-		multilineVal = strings.TrimSpace(multilineVal)
-		multilineKey = c(w, color.FgBlue).Sprintf(`"%v"`, multilineKey)
 		if msg != "..." {
 			ents += " ..."
 		}
+
+		// Proper indentation.
+		lines := strings.Split(multilineVal, "\n")
+		for i, line := range lines[1:] {
+			if line != "" {
+				lines[i+1] = strings.Repeat(" ", len(multilineKey)+4) + line
+			}
+		}
+		multilineVal = strings.Join(lines, "\n")
+
+		multilineKey = c(w, color.FgBlue).Sprintf(`"%v"`, multilineKey)
 		ents += fmt.Sprintf("\n%v: %v", multilineKey, multilineVal)
 	}
 

internal/entryhuman/entry_test.go

@@ -44,7 +44,7 @@ func TestEntry(t *testing.T) {
 			Level:   slog.LevelInfo,
 		}, `0001-01-01 00:00:00.000 [INFO]	<.:0>	...
 "msg": line1
-line2`)
+       line2`)
 	})
 
 	t.Run("multilineField", func(t *testing.T) {
@@ -56,7 +56,7 @@ line2`)
 			Fields:  slog.M(slog.F("field", "line1\nline2")),
 		}, `0001-01-01 00:00:00.000 [INFO]	<.:0>	msg ...
 "field": line1
-line2`)
+         line2`)
 	})
 
 	t.Run("named", func(t *testing.T) {

sloggers/sloghuman/sloghuman_test.go

@@ -24,5 +24,5 @@ func TestMake(t *testing.T) {
 	et, rest, err := entryhuman.StripTimestamp(b.String())
 	assert.Success(t, "strip timestamp", err)
 	assert.False(t, "timestamp", et.IsZero())
-	assert.Equal(t, "entry", " [INFO]\t<sloghuman_test.go:21>\t...\t{\"wowow\": \"me\\nyou\"}\n  \"msg\": line1\n\n  line2\n", rest)
+	assert.Equal(t, "entry", " [INFO]\t<sloghuman_test.go:21>\t...\t{\"wowow\": \"me\\nyou\"}\n  \"msg\": line1\n\n         line2\n", rest)
 }

sloggers/slogtest/assert/assert.go

@@ -11,6 +11,8 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/kylelemons/godebug/pretty"
+
 	"cdr.dev/slog"
 	"cdr.dev/slog/sloggers/slogtest"
 )
@@ -30,8 +32,7 @@ func Equal(t testing.TB, name string, exp, act interface{}) {
 	if !reflect.DeepEqual(exp, act) {
 		slogtest.Fatal(t, "unexpected value",
 			slog.F("name", name),
-			slog.F("exp", exp),
-			slog.F("act", act),
+			slog.F("diff", pretty.Compare(exp, act)),
 		)
 	}
 }