fix: multipleOf validation for large integers beyond i64::MAX

Signed-off-by: Dmitry Dygalo <[email protected]>

Author: Stranger6667

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- `multipleOf` validation for large u64 values beyond `i64::MAX` with `arbitrary-precision` feature.
+
 ## [0.37.4] - 2025-11-30
 
 ### Fixed

crates/jsonschema-py/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- `multipleOf` validation for large integers beyond `i64::MAX`.
+
 ## [0.37.4] - 2025-11-30
 
 ### Fixed

crates/jsonschema/src/ext/numeric.rs

@@ -87,6 +87,20 @@ pub(crate) fn is_multiple_of_float(value: &Number, multiple: f64) -> bool {
 }
 
 pub(crate) fn is_multiple_of_integer(value: &Number, multiple: f64) -> bool {
+    // For large u64 values beyond i64::MAX, as_f64() loses precision (since they exceed 2^53).
+    // Use u64 arithmetic directly for these cases.
+    #[cfg(feature = "arbitrary-precision")]
+    if let Some(v) = value.as_u64() {
+        // If as_i64() returns None, the value is > i64::MAX, which is > 2^53
+        // and therefore cannot be exactly represented in f64
+        if value.as_i64().is_none() {
+            // Use u64 modulo when the divisor fits in u64
+            if multiple > 0.0 && multiple <= u64::MAX as f64 && multiple.fract() == 0.0 {
+                return (v % (multiple as u64)) == 0;
+            }
+        }
+    }
+
     if let Some(value_f64) = value.as_f64() {
         // As the divisor has its fractional part as zero, then any value with a non-zero
         // fractional part can't be a multiple of this divisor, therefore it is short-circuited

crates/jsonschema/src/keywords/multiple_of.rs

@@ -431,6 +431,12 @@ mod tests {
         #[test_case(r#"{"multipleOf": 2}"#, "1e1000", true; "huge scientific integer is even")]
         #[test_case(r#"{"multipleOf": 3}"#, "1e1000", false; "10^1000 not multiple of 3")]
         #[test_case(r#"{"multipleOf": 0.5}"#, "1e1000", true; "huge scientific integer multiple of 0.5")]
+        // Regression test: u64 values beyond i64::MAX lose precision when converted to f64.
+        // 9223372036854775870 ends in '0' and IS a multiple of 10, but when converted to f64
+        // it becomes 9223372036854775808 which ends in '8' and is NOT a multiple of 10.
+        #[test_case(r#"{"multipleOf": 10}"#, "9223372036854775870", true; "u64 beyond i64 max multiple of 10")]
+        #[test_case(r#"{"multipleOf": 10}"#, "9223372036854775871", false; "u64 beyond i64 max not multiple of 10")]
+        #[test_case(r#"{"type": "integer", "minimum": 9223372036854775800, "maximum": 9223372036854775900, "multipleOf": 10}"#, "9223372036854775870", true; "combined schema with u64 beyond i64 max")]
         #[test_case(r#"{"multipleOf": 18446744073709551616}"#, "36893488147419103232", true; "large bigint multiple")]
         #[test_case(r#"{"multipleOf": 18446744073709551616}"#, "18446744073709551617", false; "large bigint non-multiple")]
         #[test_case(r#"{"multipleOf": 18446744073709551616}"#, "100", false; "small int not multiple of large")]