correctly compare numeric prerelease values larger than int64

version.go

@@ -258,25 +258,50 @@ func allZero(segs []int64) bool {
 	return true
 }
 
-func comparePart(preSelf string, preOther string) int {
-	if preSelf == preOther {
-		return 0
+// isNumericIdentifier reports whether s consists entirely of ASCII digits.
+// Per the semver spec, numeric identifiers must not have leading zeroes,
+// so a longer string always represents a larger value and lexicographic
+// order equals numeric order for strings of the same length.
+func isNumericIdentifier(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		if c < '0' || c > '9' {
+			return false
+		}
 	}
+	return true
+}
 
-	var selfInt int64
-	selfNumeric := true
-	selfInt, err := strconv.ParseInt(preSelf, 10, 64)
-	if err != nil {
-		selfNumeric = false
+// compareNumericIdentifiers compares two all-digit strings by value without
+// parsing them into a fixed-width integer type, correctly handling values
+// larger than math.MaxInt64.
+func compareNumericIdentifiers(a, b string) int {
+	if len(a) != len(b) {
+		if len(a) > len(b) {
+			return 1
+		}
+		return -1
 	}
+	// Same length: lexicographic order equals numeric order.
+	if a > b {
+		return 1
+	}
+	if a < b {
+		return -1
+	}
+	return 0
+}
 
-	var otherInt int64
-	otherNumeric := true
-	otherInt, err = strconv.ParseInt(preOther, 10, 64)
-	if err != nil {
-		otherNumeric = false
+func comparePart(preSelf string, preOther string) int {
+	if preSelf == preOther {
+		return 0
 	}
 
+	selfNumeric := isNumericIdentifier(preSelf)
+	otherNumeric := isNumericIdentifier(preOther)
+
 	// if a part is empty, we use the other to decide
 	if preSelf == "" {
 		if otherNumeric {
@@ -296,9 +321,9 @@ func comparePart(preSelf string, preOther string) int {
 		return -1
 	} else if !selfNumeric && otherNumeric {
 		return 1
-	} else if !selfNumeric && !otherNumeric && preSelf > preOther {
-		return 1
-	} else if selfInt > otherInt {
+	} else if selfNumeric && otherNumeric {
+		return compareNumericIdentifiers(preSelf, preOther)
+	} else if preSelf > preOther {
 		return 1
 	}
 

version_test.go

@@ -390,6 +390,12 @@ func TestComparePreReleases(t *testing.T) {
 		{"v1.2-beta.1", "v1.2-beta.2", -1},
 		{"v3.2-alpha.1", "v3.2-alpha", 1},
 		{"v3.2-rc.1-1-g123", "v3.2-rc.2", 1},
+		// Numeric identifiers exceeding math.MaxInt64 (9223372036854775807)
+		{"1.0-9223372036854775808", "1.0-9223372036854775807", 1},
+		{"1.0-9223372036854775807", "1.0-9223372036854775808", -1},
+		{"1.0-9223372036854775808", "1.0-9223372036854775808", 0},
+		{"1.0-99999999999999999999", "1.0-9999999999999999999", 1},
+		{"1.0-9999999999999999999", "1.0-99999999999999999999", -1},
 	}
 
 	for _, tc := range cases {