Add func DictObject (#1460)

Allows fields to be used to construct `ObjectMarshaler`s that can then
be used with other functions like `func Objects`. Link to issue:
#1458

---------

Co-authored-by: Abhinav Gupta <mail@abhinavg.net>

example_test.go

@@ -388,6 +388,51 @@ func ExampleObjects() {
 	// {"level":"debug","msg":"opening connections","addrs":[{"ip":"123.45.67.89","port":4040},{"ip":"127.0.0.1","port":4041},{"ip":"192.168.0.1","port":4042}]}
 }
 
+func ExampleDictObject() {
+	logger := zap.NewExample()
+	defer logger.Sync()
+
+	// Use DictObject to create zapcore.ObjectMarshaler implementations from Field arrays,
+	// then use the Object and Objects field constructors to turn them back into a Field.
+
+	logger.Debug("worker received job",
+		zap.Object("w1",
+			zap.DictObject(
+				zap.Int("id", 402000),
+				zap.String("description", "compress image data"),
+				zap.Int("priority", 3),
+			),
+		))
+
+	d1 := 68 * time.Millisecond
+	d2 := 79 * time.Millisecond
+	d3 := 57 * time.Millisecond
+
+	logger.Info("worker status checks",
+		zap.Objects("job batch enqueued",
+			[]zapcore.ObjectMarshaler{
+				zap.DictObject(
+					zap.String("worker", "w1"),
+					zap.Int("load", 419),
+					zap.Duration("latency", d1),
+				),
+				zap.DictObject(
+					zap.String("worker", "w2"),
+					zap.Int("load", 520),
+					zap.Duration("latency", d2),
+				),
+				zap.DictObject(
+					zap.String("worker", "w3"),
+					zap.Int("load", 310),
+					zap.Duration("latency", d3),
+				),
+			},
+		))
+	// Output:
+	// {"level":"debug","msg":"worker received job","w1":{"id":402000,"description":"compress image data","priority":3}}
+	// {"level":"info","msg":"worker status checks","job batch enqueued":[{"worker":"w1","load":419,"latency":"68ms"},{"worker":"w2","load":520,"latency":"79ms"},{"worker":"w3","load":310,"latency":"57ms"}]}
+}
+
 func ExampleObjectValues() {
 	logger := zap.NewExample()
 	defer logger.Sync()

field.go

@@ -431,6 +431,13 @@ func (d dictObject) MarshalLogObject(enc zapcore.ObjectEncoder) error {
 	return nil
 }
 
+// DictObject constructs a [zapcore.ObjectMarshaler] with the given list of fields.
+// The resulting object marshaler can be used as input to [Object], [Objects], or
+// any other functions that expect an object marshaler.
+func DictObject(val ...Field) zapcore.ObjectMarshaler {
+	return dictObject(val)
+}
+
 // We discovered an issue where zap.Any can cause a performance degradation
 // when used in new goroutines.
 //

field_test.go

@@ -314,3 +314,45 @@ func TestDict(t *testing.T) {
 		})
 	}
 }
+
+func TestDictObject(t *testing.T) {
+	tests := []struct {
+		desc     string
+		field    Field
+		expected any
+	}{
+		{
+			"empty",
+			Object("", DictObject()),
+			map[string]any{},
+		},
+		{
+			"object",
+			Object("", DictObject(String("k", "v"))),
+			map[string]any{"k": "v"},
+		},
+		{
+			"objects",
+			Objects("", []zapcore.ObjectMarshaler{
+				DictObject(String("k", "v")),
+				DictObject(String("k2", "v2")),
+			}),
+			[]any{
+				map[string]any{"k": "v"},
+				map[string]any{"k2": "v2"},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			enc := zapcore.NewMapObjectEncoder()
+			tt.field.Key = "k"
+			tt.field.AddTo(enc)
+			assert.Equal(t, tt.expected, enc.Fields["k"], "unexpected map contents")
+			assert.Len(t, enc.Fields, 1, "found extra keys in map: %v", enc.Fields)
+
+			assertCanBeReused(t, tt.field)
+		})
+	}
+}

zapcore/field_test.go

@@ -320,6 +320,16 @@ func TestEquals(t *testing.T) {
 			b:    zap.Dict("k", zap.String("a", "d")),
 			want: false,
 		},
+		{
+			a:    zap.Object("k", zap.DictObject(zap.String("a", "b"))),
+			b:    zap.Object("k", zap.DictObject(zap.String("a", "b"))),
+			want: true,
+		},
+		{
+			a:    zap.Object("k", zap.DictObject(zap.String("a", "b"))),
+			b:    zap.Object("k", zap.DictObject(zap.String("a", "d"))),
+			want: false,
+		},
 	}
 
 	for _, tt := range tests {