Encode non-fatal floats as integers in canonical mode

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

canonical/json/encode.go

@@ -526,7 +526,13 @@ func (bits floatEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
 	if math.IsInf(f, 0) || math.IsNaN(f) || (e.canonical && math.Floor(f) != f) {
 		e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, int(bits))})
 	}
-	b := strconv.AppendFloat(e.scratch[:0], f, 'g', -1, int(bits))
+
+	var b []byte
+	if e.canonical {
+		b = strconv.AppendInt(e.scratch[:0], int64(f), 10)
+	} else {
+		b = strconv.AppendFloat(e.scratch[:0], f, 'g', -1, int(bits))
+	}
 	if quoted {
 		e.WriteByte('"')
 	}

canonical/json/encode_test.go

@@ -589,3 +589,17 @@ func TestCanonicalFloatError(t *testing.T) {
 		t.Errorf("want float error, got nil")
 	}
 }
+
+func TestCanonicalFloatAsInt(t *testing.T) {
+	in := struct{ A float64 }{1234567}
+
+	b, err := MarshalCanonical(in)
+	if err != nil {
+		t.Fatalf("Marshal(%q): %v", in, err)
+	}
+	out := string(b)
+	expected := `{"A":1234567}`
+	if out != expected {
+		t.Errorf("Marshal(%q) = %#q, want %#q", in, out, expected)
+	}
+}