fix: changed format_units to return a String and preserve the decimal

places
gakonst · Nov 24, 2021 · d57bb73 · d57bb73
1 parent 57da256
commit d57bb73
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Showing 2 changed files with 29 additions and 4 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -11,6 +11,7 @@
 - Add EIP-712 `sign_typed_data` signer method; add ethers-core type `Eip712`
   trait and derive macro in ethers-derive-eip712
   [#481](https://github.com/gakonst/ethers-rs/pull/481)
+- Fix `format_units` to return a `String` of representing a decimal point float such that the decimal places don't get truncated. [597](https://github.com/gakonst/ethers-rs/pull/597)
 
 ### 0.5.3
 

diff --git a/ethers-core/src/utils/mod.rs b/ethers-core/src/utils/mod.rs
@@ -58,10 +58,25 @@ pub fn format_ether<T: Into<U256>>(amount: T) -> U256 {
 }
 
 /// Divides the provided amount with 10^{units} provided.
-pub fn format_units<T: Into<U256>, K: Into<Units>>(amount: T, units: K) -> U256 {
+///
+/// ```
+/// use ethers_core::{types::U256, utils::format_units};
+///
+/// let eth = format_units(1395633240123456000_u128, "ether");
+/// assert_eq!(eth.parse::<f64>().unwrap(), 1.395633240123456);
+///
+/// let eth = format_units(U256::from_dec_str("1395633240123456000").unwrap(), "ether");
+/// assert_eq!(eth.parse::<f64>().unwrap(), 1.395633240123456);
+///
+/// let eth = format_units(U256::from_dec_str("1395633240123456789").unwrap(), "ether");
+/// assert_eq!(eth, "1.395633240123456789");
+/// ```
+pub fn format_units<T: Into<U256>, K: Into<Units>>(amount: T, units: K) -> String {
     let units = units.into();
     let amount = amount.into();
-    amount / 10u64.pow(units.as_num())
+    let amount_decimals = amount % U256::from(10_u128.pow(units.as_num()));
+    let amount_integer = amount / U256::from(10_u128.pow(units.as_num()));
+    amount_integer.to_string() + "." + &amount_decimals.to_string()
 }
 
 /// Converts the input to a U256 and converts from Ether to Wei.
@@ -367,10 +382,19 @@ mod tests {
     #[test]
     fn test_format_units() {
         let gwei_in_ether = format_units(WEI_IN_ETHER, 9);
-        assert_eq!(gwei_in_ether.as_u64(), 1e9 as u64);
+        assert_eq!(gwei_in_ether.parse::<f64>().unwrap() as u64, 1e9 as u64);
 
         let eth = format_units(WEI_IN_ETHER, "ether");
-        assert_eq!(eth.as_u64(), 1);
+        assert_eq!(eth.parse::<f64>().unwrap() as u64, 1);
+
+        let eth = format_units(1395633240123456000_u128, "ether");
+        assert_eq!(eth.parse::<f64>().unwrap(), 1.395633240123456);
+
+        let eth = format_units(U256::from_dec_str("1395633240123456000").unwrap(), "ether");
+        assert_eq!(eth.parse::<f64>().unwrap(), 1.395633240123456);
+
+        let eth = format_units(U256::from_dec_str("1395633240123456789").unwrap(), "ether");
+        assert_eq!(eth, "1.395633240123456789");
     }
 
     #[test]