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fix(validation): correct int-width bound in GetIntFromInterface #538

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Merged
Phil-Browne merged 1 commit into from
Jul 13, 2026
Merged

fix(validation): correct int-width bound in GetIntFromInterface #538

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12 changes: 9 additions & 3 deletions internal/validation/conversion.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,9 +14,15 @@ func GetIntFromInterface(value interface{}) (int, bool) {
return v, true
case float64:
// Reject fractional or out-of-range values rather than silently truncating
// JSON-derived numbers (e.g. 3.9 -> 3). Bounds use platform int width so
// 32-bit targets (js/wasm) don't accept values that overflow int.
if v != math.Trunc(v) || v < math.MinInt || v > math.MaxInt {
// JSON-derived numbers (e.g. 3.9 -> 3). Bounds use math.MaxInt so this
// stays correct across platform int widths.
//
// float64(math.MaxInt) itself rounds up to 2^63 on platforms where int is
// 64 bits (2^63-1 isn't exactly representable), so comparing v against it
// directly would wrongly reject the true max int on platforms where MaxInt
// fits exactly in a float64 (e.g. a 32-bit int). Add 1 to get the true
// exclusive upper bound on either width.
if v != math.Trunc(v) || v < math.MinInt || v >= float64(math.MaxInt)+1 {
return 0, false
}
return int(v), true
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7 changes: 7 additions & 0 deletions internal/validation/conversion_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,11 @@ import (
)

func TestGetIntFromInterface(t *testing.T) {
// Derived from math.MaxInt (rather than a hardcoded 2^63) so the boundary
// cases stay in range regardless of platform int width.
nearMaxInt := float64(math.MaxInt) - 4096
justAboveMaxInt := float64(math.MaxInt) + 4096

tests := []struct {
name string
value interface{}
Expand All @@ -20,6 +25,8 @@ func TestGetIntFromInterface(t *testing.T) {
{"float64 whole", float64(10), 10, true},
{"float64 fractional rejected", float64(3.9), 0, false},
{"float64 above int range rejected", float64(math.MaxInt) * 2, 0, false},
{"float64 just above max int rejected", justAboveMaxInt, 0, false},
{"float64 just below max int accepted", nearMaxInt, int(nearMaxInt), true},
{"numeric string", "123", 123, true},
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Phil-Browne marked this conversation as resolved.
{"negative numeric string", "-5", -5, true},
{"empty string", "", 0, false},
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