Allow preset overrides

packages/params/README.md

@@ -71,6 +71,7 @@ Important Notes:
 - Interacting with and understanding the active preset is only necessary in very limited testing environments, eg: for ephemeral testnets
 - The `minimal` preset is NOT compatible with the `mainnet` preset.
 - using `setActivePreset` may be dangerous, and only should be run once before loading any other libraries. All downstream Lodestar libraries expect the active preset to never change.
+- Preset values can be overriden by executing `setCustomPreset(presetName: PresetName, overrides: Partial<BeaconPreset>)` which in turn calls `setActivePreset`.
 
 ## License
 

packages/params/src/index.ts

@@ -3,7 +3,7 @@ import {preset as mainnet} from "./presets/mainnet/index.js";
 import {preset as minimal} from "./presets/minimal/index.js";
 import {preset as gnosis} from "./presets/gnosis/index.js";
 import {presetStatus} from "./presetStatus.js";
-import {userSelectedPreset} from "./setPreset.js";
+import {userSelectedPreset, userOverrides} from "./setPreset.js";
 
 export * from "./interface/index.js";
 export {ForkName, ForkSeq} from "./forkName.js";
@@ -83,7 +83,7 @@ export const {
   MAX_TRANSACTIONS_PER_PAYLOAD,
   BYTES_PER_LOGS_BLOOM,
   MAX_EXTRA_DATA_BYTES,
-} = presets[ACTIVE_PRESET];
+} = {...presets[ACTIVE_PRESET], ...userOverrides};
 
 ////////////
 // Constants

packages/params/src/setPreset.ts

@@ -1,5 +1,6 @@
 import {PresetName} from "./presetName.js";
 import {presetStatus} from "./presetStatus.js";
+import {BeaconPreset} from "./interface/index.js";
 
 export {PresetName};
 
@@ -38,3 +39,14 @@ console.log({SLOTS_PER_EPOCH})
 
   userSelectedPreset = presetName;
 }
+
+export let userOverrides: Partial<BeaconPreset> | null = null;
+
+/**
+ * @param presetName - the preset to use as a base
+ * @param overrides - customized fields
+ */
+export function setCustomPreset(presetName: PresetName, overrides: Partial<BeaconPreset>): void {
+  setActivePreset(presetName);
+  userOverrides = overrides;
+}

packages/params/test/e2e/overridePreset.test.ts

@@ -0,0 +1,36 @@
+import path from "node:path";
+import util from "node:util";
+import child from "node:child_process";
+import {fileURLToPath} from "node:url";
+import {expect, use} from "chai";
+import chaiAsPromised from "chai-as-promised";
+
+const scriptNames = {
+  ok: "overridePresetOk.ts",
+  error: "overridePresetError.ts",
+};
+
+use(chaiAsPromised);
+
+const exec = util.promisify(child.exec);
+
+// Global variable __dirname no longer available in ES6 modules.
+// Solutions: https://stackoverflow.com/questions/46745014/alternative-for-dirname-in-node-js-when-using-es6-modules
+// eslint-disable-next-line @typescript-eslint/naming-convention
+const __dirname = path.dirname(fileURLToPath(import.meta.url));
+const tsNodeBinary = path.join(__dirname, "../../../../node_modules/.bin/ts-node-esm");
+
+describe("Override preset", function () {
+  // Allow time for ts-node to compile Typescript source
+  this.timeout(30_000);
+
+  it("Should correctly override preset", async () => {
+    await exec(`${tsNodeBinary} ${path.join(__dirname, scriptNames.ok)}`);
+  });
+
+  it("Should throw trying to override preset in the wrong order", async () => {
+    await expect(exec(`${tsNodeBinary} ${path.join(__dirname, scriptNames.error)}`)).to.be.rejectedWith(
+      "Lodestar preset is already frozen"
+    );
+  });
+});

packages/params/test/e2e/overridePresetError.ts

@@ -0,0 +1,10 @@
+// This script is should be run in an e2e !!
+// It demostrates how NOT to change the Lodestar preset
+
+// 1. Import from not only @lodestar/params/setPreset will trigger an error
+import {SLOTS_PER_EPOCH} from "../../lib/index.js";
+import {setActivePreset, PresetName} from "../../lib/setPreset.js";
+// This line should throw
+setActivePreset(PresetName.minimal);
+
+SLOTS_PER_EPOCH;

packages/params/test/e2e/overridePresetOk.ts

@@ -0,0 +1,17 @@
+/* eslint import/order: "off" */
+// This script is should be run in an e2e !!
+// It demostrates how to properly change the Lodestar preset safely
+
+// 1. Import from @lodestar/params/setPreset only
+import {setCustomPreset, PresetName} from "../../src/setPreset.js";
+// eslint-disable-next-line @typescript-eslint/naming-convention
+setCustomPreset(PresetName.minimal, {SLOTS_PER_EPOCH: 2});
+
+// 2. Import from any other @lodestar/params paths
+import {expect} from "chai";
+
+const {SLOTS_PER_EPOCH, BASE_REWARD_FACTOR} = await import("../../src/index.js");
+
+expect(SLOTS_PER_EPOCH).to.equal(2, "SLOTS_PER_EPOCH should have overriden preset value");
+expect(BASE_REWARD_FACTOR).to.equal(64, "BASE_REWARD_FACTOR should have preset value");
+expect(process.env.LODESTAR_PRESET).to.equal(undefined, "LODESTAR_PRESET ENV must not be set");