Preserve string form if the original value can be fully represented

demo/main.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"gomodules.xyz/resource-quantity"
+)
+
+func main() {
+	q := resource.MustParse("1.1Gi")
+	if data, err := json.Marshal(q); err != nil {
+		panic(err)
+	} else {
+		fmt.Println(string(data))
+	}
+}

quantity.go

@@ -365,6 +365,13 @@ func ParseQuantity(str string) (Quantity, error) {
 		amount.Neg(amount)
 	}
 
+	copyAmount := new(inf.Dec)
+	if sign == -1 {
+		copyAmount.Neg(amount)
+	} else {
+		copyAmount.Set(amount)
+	}
+
 	// This rounds non-zero values up to the minimum representable value, under the theory that
 	// if you want some resources, you should get some resources, even if you asked for way too small
 	// of an amount.  Arguably, this should be inf.RoundHalfUp (normal rounding), but that would have
@@ -387,7 +394,11 @@ func ParseQuantity(str string) (Quantity, error) {
 		amount.Neg(amount)
 	}
 
-	return Quantity{d: infDecAmount{amount}, Format: format}, nil
+	q := Quantity{d: infDecAmount{amount}, Format: format}
+	if copyAmount.Cmp(amount) == 0 {
+		q.s = str
+	}
+	return q, nil
 }
 
 // DeepCopy returns a deep-copy of the Quantity value.  Note that the method

quantity_test.go

@@ -725,7 +725,7 @@ func TestQuantityString(t *testing.T) {
 		{decQuantity(0, 0, BinarySI), "0", ""},
 		{decQuantity(1, 9, DecimalExponent), "1e9", ".001e12"},
 		{decQuantity(1, -3, DecimalExponent), "1e-3", "0.001e0"},
-		{decQuantity(1, -9, DecimalExponent), "1e-9", "1000e-12"},
+		{decQuantity(1, -9, DecimalExponent), "1e-9", ""},
 		{decQuantity(80, -3, DecimalExponent), "80e-3", ""},
 		{decQuantity(300, 6, DecimalExponent), "300e6", ""},
 		{decQuantity(1, 12, DecimalExponent), "1e12", ""},
@@ -794,11 +794,12 @@ func TestQuantityParseEmit(t *testing.T) {
 		{"1Ki", "1Ki"},
 		{"1Mi", "1Mi"},
 		{"1Gi", "1Gi"},
+		{"1.1Gi", "1.1Gi"},
 		{"1024Mi", "1Gi"},
 		{"1000M", "1G"},
-		{".001Ki", "1024m"},
-		{".000001Ki", "1024u"},
-		{".000000001Ki", "1024n"},
+		{".001Ki", ".001Ki"},
+		{".000001Ki", ".000001Ki"},
+		{".000000001Ki", ".000000001Ki"},
 		{".000000000001Ki", "2n"},
 	}