fix: allow usage of decimal string encoding for fields larger than a i128

crates/noirc_abi/Cargo.toml

@@ -14,7 +14,9 @@ toml.workspace = true
 serde_json = "1.0"
 serde.workspace = true
 thiserror.workspace = true
+num-bigint = "0.4"
+num-traits = "0.2"
 
 [dev-dependencies]
 strum = "0.24"
-strum_macros = "0.24"
+strum_macros = "0.24"

crates/noirc_abi/src/input_parser/mod.rs

@@ -1,13 +1,16 @@
-mod json;
-mod toml;
-
+use num_bigint::BigUint;
+use num_traits::Num;
 use std::collections::BTreeMap;
 
 use acvm::FieldElement;
 use serde::Serialize;
 
 use crate::errors::InputParserError;
 use crate::{Abi, AbiType};
+
+mod json;
+mod toml;
+
 /// This is what all formats eventually transform into
 /// For example, a toml file will parse into TomlTypes
 /// and those TomlTypes will be mapped to Value
@@ -183,20 +186,52 @@ fn parse_str_to_field(value: &str) -> Result<FieldElement, InputParserError> {
     if value.starts_with("0x") {
         FieldElement::from_hex(value).ok_or_else(|| InputParserError::ParseHexStr(value.to_owned()))
     } else {
-        value
-            .parse::<i128>()
+        BigUint::from_str_radix(value, 10)
             .map_err(|err_msg| InputParserError::ParseStr(err_msg.to_string()))
-            .map(FieldElement::from)
+            // Note that we're reducing here. Should we reject inputs that don't fit in the field?
+            .map(field_from_big_uint)
     }
 }
 
+fn field_from_big_uint(bigint: BigUint) -> FieldElement {
+    FieldElement::from_be_bytes_reduce(&bigint.to_bytes_be())
+}
+
 #[cfg(test)]
 mod test {
+    use acvm::FieldElement;
+    use num_bigint::BigUint;
+
     use super::parse_str_to_field;
 
+    fn big_uint_from_field(field: FieldElement) -> BigUint {
+        BigUint::from_bytes_be(&field.to_be_bytes())
+    }
+
     #[test]
     fn parse_empty_str_fails() {
         // Check that this fails appropriately rather than being treated as 0, etc.
         assert!(parse_str_to_field("").is_err());
     }
+
+    #[test]
+    fn parse_fields_from_strings() {
+        let fields = vec![
+            FieldElement::zero(),
+            FieldElement::one(),
+            FieldElement::from(u128::MAX) + FieldElement::one(),
+            // Equivalent to `FieldElement::modulus() - 1`
+            -FieldElement::one(),
+        ];
+
+        for field in fields {
+            let hex_field = format!("0x{}", field.to_hex());
+            let field_from_hex = parse_str_to_field(&hex_field).unwrap();
+            assert_eq!(field_from_hex, field);
+
+            let dec_field = big_uint_from_field(field).to_string();
+            let field_from_dec = parse_str_to_field(&dec_field).unwrap();
+            assert_eq!(field_from_dec, field);
+        }
+    }
 }