fix: zscore return 0 when double value is too small (#344)

* fix: zscore return 0 when double value is too small

* "good enough" float-to-string conversion

---------

Co-authored-by: Harmen <alicebob@lijzij.de>

cmd_sorted_set_test.go

@@ -1089,9 +1089,15 @@ func TestSortedSetScore(t *testing.T) {
 	{
 		s.ZAdd("z2", 1, "one")
 		s.ZAdd("z2", 2, "two")
+		s.ZAdd("z2", 0.000000000000000000000000000000000000000000000000000000000000000025339988685347402, "small")
 		score, err := s.ZScore("z2", "two")
 		ok(t, err)
 		equals(t, 2.0, score)
+
+		score, err = s.ZScore("z2", "small")
+		ok(t, err)
+		equals(t, 0.000000000000000000000000000000000000000000000000000000000000000025339988685347402, score)
+
 	}
 
 	t.Run("errors", func(t *testing.T) {

integration/sorted_set_test.go

@@ -90,6 +90,14 @@ func TestSortedSet(t *testing.T) {
 		c.Do("ZRANGEBYLEX", "z", "[a", "[z")
 		c.Do("ZRANGE", "z", "0", "-1", "WITHSCORES")
 	})
+
+	testRaw(t, func(c *client) {
+		// very small values
+		c.Do("ZADD", "a_zset", "1.2", "one")
+		c.Do("ZADD", "a_zset", "incr", "1.2", "one")
+		c.DoRounded(1, "ZADD", "a_zset", "incr", "1.2", "one") // real: 3.5999999999999996, mini: 3.6
+		c.Do("ZADD", "a_zset", "incr", "1.2", "one")
+	})
 }
 
 func TestSortedSetAdd(t *testing.T) {

server/server.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"math"
 	"net"
+	"strconv"
 	"strings"
 	"sync"
 	"unicode"
@@ -478,28 +479,13 @@ func (w *Writer) Flush() {
 }
 
 // formatFloat formats a float the way redis does (sort-of)
+// Redis uses a method called "grisu2", which gives slightly different output.
 func formatFloat(v float64) string {
 	if math.IsInf(v, 1) {
 		return "inf"
 	}
 	if math.IsInf(v, -1) {
 		return "-inf"
 	}
-	return stripZeros(fmt.Sprintf("%.12f", v))
-}
-
-func stripZeros(sv string) string {
-	for strings.Contains(sv, ".") {
-		if sv[len(sv)-1] != '0' {
-			break
-		}
-		// Remove trailing 0s.
-		sv = sv[:len(sv)-1]
-		// Ends with a '.'.
-		if sv[len(sv)-1] == '.' {
-			sv = sv[:len(sv)-1]
-			break
-		}
-	}
-	return sv
+	return strconv.FormatFloat(v, 'g', 16, 64)
 }

server/server_test.go

@@ -236,3 +236,41 @@ func TestTLS(t *testing.T) {
 		t.Errorf("have: %s, want: %s", have, want)
 	}
 }
+
+func TestFormatFloat(t *testing.T) {
+	eq := func(t *testing.T, want string, n float64) {
+		t.Helper()
+		have := formatFloat(n)
+		if have != want {
+			t.Errorf("have: %s, want: %s", have, want)
+		}
+	}
+
+	eq(t, "1", 1.0)
+	eq(t, "0.0001", 0.0001) // checked
+	eq(t, "1.1", 1.1)
+	eq(t, "1.01", 1.01)
+	eq(t, "1.001", 1.001)
+	eq(t, "1.0001", 1.0001)
+	// real: "2.5339988685347402e-65"
+	eq(t, "2.53399886853474e-65", 0.000000000000000000000000000000000000000000000000000000000000000025339988685347402)
+	// real: "2.5339988685347402e-65"
+	eq(t, "2.53399886853474e-65", 2.5339988685347402e-65)
+	eq(t, "3479099956230698", 3479099956230698)
+	// real: "3.479099956230698e+7"
+	eq(t, "34790999.56230698", 34790999.56230698123123123)
+
+	eq(t, "1.2", 1.2)
+	eq(t, "2.4", 2*1.2)
+	eq(t, "3.6", 3*1.2)
+	eq(t, "4.8", 4*1.2)
+	a := 1.2
+	eq(t, "1.2", a)
+	a += 1.2
+	eq(t, "2.4", a)
+	a += 1.2
+	// real: "3.5999999999999996"
+	eq(t, "3.6", a)
+	a += 1.2
+	eq(t, "4.8", a)
+}