fix(wasm-shim): correctly round decimals

Author: TheLostLambda

crates/wasm-shim/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasm-shim"
-version = "0.1.1"
+version = "0.1.2"
 edition = "2021"
 
 [lib]
@@ -12,6 +12,7 @@ muropeptide = { path = "../muropeptide" }
 polychem = { path = "../polychem" }
 smithereens = { path = "../smithereens" }
 console_error_panic_hook = "0.1.7"
+rust_decimal = "1.36.0"
 
 [lints]
 workspace = true

crates/wasm-shim/src/lib.rs

@@ -1,5 +1,6 @@
 use muropeptide::{Muropeptide, POLYMERIZER};
 use polychem::{ChargedParticle, Massive};
+use rust_decimal::Decimal;
 use smithereens::Dissociable;
 use std::fmt::Write;
 use wasm_bindgen::prelude::*;
@@ -35,7 +36,7 @@ impl Peptidoglycan {
     #[must_use]
     pub fn monoisotopic_mass(&self) -> String {
         let mass = self.0.monoisotopic_mass();
-        format!("{mass:.6}")
+        decimal_round_workaround(mass, 6)
     }
 
     #[must_use]
@@ -53,8 +54,15 @@ impl Peptidoglycan {
         let mut csv = String::new();
         writeln!(&mut csv, "Structure,Ion M/Z").unwrap();
         for (structure, mz) in fragments {
-            writeln!(&mut csv, r#""{structure}",{mz:.6}"#).unwrap();
+            let mz = decimal_round_workaround(mz, 6);
+            writeln!(&mut csv, r#""{structure}",{mz}"#).unwrap();
         }
         csv
     }
 }
+
+// FIXME: Really this should be fixed in `rust_decimal`...
+fn decimal_round_workaround(value: impl Into<Decimal>, decimal_points: u32) -> String {
+    let value = value.into().round_dp(decimal_points);
+    format!("{value}")
+}