From 3a768b9c99a83bbb7c3d5d5ad36061d8ed8cdbb5 Mon Sep 17 00:00:00 2001
From: x3ccd4828 <492528+x3ccd4828@users.noreply.github.com>
Date: Wed, 24 Nov 2021 04:07:18 -0500
Subject: [PATCH] Fix parse units (#597)

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

* chore: fix changelog

Co-authored-by: Georgios Konstantopoulos <me@gakonst.com>
---
 CHANGELOG.md                 |  4 ++++
 ethers-core/src/utils/mod.rs | 32 ++++++++++++++++++++++++++++----
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93f01e62..df2a976b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## ethers-core
 
+- 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)
+
 ### Unreleased
 
 ### 0.6.0
diff --git a/ethers-core/src/utils/mod.rs b/ethers-core/src/utils/mod.rs
index 0099e2e4..7b16f1a5 100644
--- 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]