Merge pull request #2922 from NomicFoundation/francovictorio/hh-631/detect-anonymous-fixtures

Don't allow using anonymous functions as fixtures

Author: fvictorio

.changeset/quick-hairs-thank.md

@@ -0,0 +1,5 @@
+---
+"@nomicfoundation/hardhat-network-helpers": patch
+---
+
+- Disallow using anonymous functions as fixtures

packages/hardhat-network-helpers/src/errors.ts

@@ -23,6 +23,20 @@ This might be caused by using nested loadFixture calls in a test, for example by
   }
 }
 
+export class FixtureAnonymousFunctionError extends CustomError {
+  constructor() {
+    super(`Anonymous functions cannot be used as fixtures.
+
+You probably did something like this:
+
+    loadFixture(async () => { ... });
+
+Instead, define a fixture function and refer to that same function in each call to loadFixture.
+
+Learn more at https://hardhat.org/hardhat-network-helpers/docs/reference#fixtures`);
+  }
+}
+
 export class OnlyHardhatNetworkError extends CustomError {
   constructor(networkName: string, version?: string) {
     let errorMessage: string = ``;

packages/hardhat-network-helpers/src/loadFixture.ts

@@ -1,6 +1,10 @@
 import type { SnapshotRestorer } from "./helpers/takeSnapshot";
 
-import { FixtureSnapshotError, InvalidSnapshotError } from "./errors";
+import {
+  FixtureAnonymousFunctionError,
+  FixtureSnapshotError,
+  InvalidSnapshotError,
+} from "./errors";
 
 type Fixture<T> = () => Promise<T>;
 
@@ -27,6 +31,10 @@ const snapshots: Array<Snapshot<any>> = [];
  * - Incorrect usage: `loadFixture(async () => { ... })`
  */
 export async function loadFixture<T>(fixture: Fixture<T>): Promise<T> {
+  if (fixture.name === "") {
+    throw new FixtureAnonymousFunctionError();
+  }
+
   const snapshot = snapshots.find((s) => s.fixture === fixture);
 
   const { takeSnapshot } = await import("./helpers/takeSnapshot");

packages/hardhat-network-helpers/test/loadFixture.ts

@@ -1,6 +1,9 @@
 import { assert } from "chai";
 
-import { FixtureSnapshotError } from "../src/errors";
+import {
+  FixtureAnonymousFunctionError,
+  FixtureSnapshotError,
+} from "../src/errors";
 import { loadFixture } from "../src/loadFixture";
 import { useEnvironment, rpcQuantityToNumber } from "./test-utils";
 
@@ -90,4 +93,18 @@ describe("loadFixture", function () {
       FixtureSnapshotError
     );
   });
+
+  it("should throw when an anonymous regular function is used", async function () {
+    await assert.isRejected(
+      loadFixture(async function () {}),
+      FixtureAnonymousFunctionError
+    );
+  });
+
+  it("should throw when an anonymous arrow function is used", async function () {
+    await assert.isRejected(
+      loadFixture(async () => {}),
+      FixtureAnonymousFunctionError
+    );
+  });
 });