feat(enc.float): define NaN and Inf

enc_float.go

@@ -1,7 +1,11 @@
 package jx
 
 // Float32 writes float32.
+//
+// NB: Infinities and NaN are represented as null.
 func (e *Encoder) Float32(v float32) { e.float(float64(v), 32) }
 
 // Float64 writes float64.
+//
+// NB: Infinities and NaN are represented as null.
 func (e *Encoder) Float64(v float64) { e.float(v, 64) }

enc_float_bits.go

@@ -9,9 +9,19 @@ import (
 	"strconv"
 )
 
-// From go std sources, strconv/ftoa.go
-
 func (e *Encoder) float(v float64, bits int) {
+	if math.IsNaN(v) || math.IsInf(v, 0) {
+		// Like in ECMA:
+		// NaN and Infinity regardless of sign are represented
+		// as the String null.
+		//
+		// JSON.stringify({"foo":NaN}) -> {"foo":null}
+		e.Null()
+		return
+	}
+
+	// From go std sources, strconv/ftoa.go:
+
 	// Convert as if by ES6 number to string conversion.
 	// This matches most other JSON generators.
 	// See golang.org/issue/6384 and golang.org/issue/14135.

float_test.go

@@ -149,3 +149,21 @@ func TestDecoder_FloatEOF(t *testing.T) {
 	_, err := d.Float32()
 	require.ErrorIs(t, err, io.ErrUnexpectedEOF)
 }
+
+func TestEncoder_FloatNanInf(t *testing.T) {
+	for _, f := range []float64{
+		math.NaN(),
+		math.Inf(-1),
+		math.Inf(1),
+	} {
+		var e Encoder
+		e.Float64(f)
+		e.More()
+		e.Float32(float32(f))
+
+		d := DecodeBytes(e.Bytes())
+		require.NoError(t, d.Null())
+		requireElem(t, d)
+		require.NoError(t, d.Null())
+	}
+}