Strip leading UTF-8 BOM before parsing package.json

Author: webpro

packages/knip/fixtures/workspaces-utf8-bom/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "@fixtures/workspaces-utf8-bom",
+  "private": true,
+  "workspaces": ["packages/*"]
+}

packages/knip/fixtures/workspaces-utf8-bom/packages/no-bom/index.ts

@@ -0,0 +1 @@
+export const a = 1;

packages/knip/fixtures/workspaces-utf8-bom/packages/no-bom/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "@fixtures/workspaces-utf8-bom__no-bom",
+  "main": "./index.ts"
+}

packages/knip/fixtures/workspaces-utf8-bom/packages/with-bom/index.ts

@@ -0,0 +1 @@
+export const b = 2;

packages/knip/fixtures/workspaces-utf8-bom/packages/with-bom/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "@fixtures/workspaces-utf8-bom__with-bom",
+  "main": "./index.ts"
+}

packages/knip/src/util/fs.ts

@@ -55,7 +55,7 @@ export const hasFileWithExtension = (cwd: string, dirName: string, extensions: s
 };
 
 export const loadJSON = async (filePath: string) => {
-  const contents = await loadFile(filePath);
+  const contents = (await loadFile(filePath)).replace(/^/, '');
   try {
     return JSON.parse(contents);
   } catch {

packages/knip/src/util/map-workspaces.ts

@@ -28,7 +28,7 @@ export default async function mapWorkspaces(cwd: string, workspaces: string[]):
     const dir = join(cwd, name);
     const manifestPath = join(cwd, match);
     try {
-      const manifestStr = await readFile(manifestPath, 'utf8');
+      const manifestStr = (await readFile(manifestPath, 'utf8')).replace(/^/, '');
       const manifest: PackageJson = JSON.parse(manifestStr);
       const pkgName = getPackageName(manifest, dir);
       const pkg: WorkspacePackage = { dir, name, pkgName, manifestPath, manifestStr, manifest };

packages/knip/test/workspaces-utf8-bom.test.ts

@@ -0,0 +1,14 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { main } from '../src/index.ts';
+import { createOptions } from './helpers/create-options.ts';
+import { resolve } from './helpers/resolve.ts';
+
+const cwd = resolve('fixtures/workspaces-utf8-bom');
+
+test('Discover workspace whose package.json starts with a UTF-8 BOM', async () => {
+  const options = await createOptions({ cwd });
+  await assert.doesNotReject(main(options));
+  const { counters } = await main(options);
+  assert.equal(counters.processed, 2);
+});