fix(cheats): correct impersonate() return semantics to match documentation (#12309)

* fix(cheats): correct impersonate() return semantics to match documentation

* clean

---------

Co-authored-by: 0xrusowsky <[email protected]>
Co-authored-by: grandizzy <[email protected]>
Co-authored-by: DaniPopes <[email protected]>

Author: 4 people

crates/anvil/src/eth/backend/cheats.rs

@@ -30,21 +30,16 @@ impl CheatsManager {
     ///
     /// Returns `true` if the account is already impersonated
     pub fn impersonate(&self, addr: Address) -> bool {
-        trace!(target: "cheats", "Start impersonating {:?}", addr);
-        let mut state = self.state.write();
+        trace!(target: "cheats", %addr, "start impersonating");
         // When somebody **explicitly** impersonates an account we need to store it so we are able
         // to return it from `eth_accounts`. That's why we do not simply call `is_impersonated()`
         // which does not check that list when auto impersonation is enabled.
-        if state.impersonated_accounts.contains(&addr) {
-            // need to check if already impersonated, so we don't overwrite the code
-            return true;
-        }
-        state.impersonated_accounts.insert(addr)
+        !self.state.write().impersonated_accounts.insert(addr)
     }
 
     /// Removes the account that from the impersonated set
     pub fn stop_impersonating(&self, addr: &Address) {
-        trace!(target: "cheats", "Stop impersonating {:?}", addr);
+        trace!(target: "cheats", %addr, "stop impersonating");
         self.state.write().impersonated_accounts.remove(addr);
     }
 
@@ -145,3 +140,16 @@ impl Precompile for CheatEcrecover {
 pub struct CheatEcrecover {
     cheats: Arc<CheatsManager>,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn impersonate_returns_false_then_true() {
+        let mgr = CheatsManager::default();
+        let addr = Address::from([1u8; 20]);
+        assert!(!mgr.impersonate(addr));
+        assert!(mgr.impersonate(addr));
+    }
+}