test: ignore TypeScript errors in 'node_modules'

Author: bradenmacdonald

jest.config.js

@@ -1,6 +1,6 @@
 const { createConfig } = require('@openedx/frontend-build');
 
-module.exports = createConfig('jest', {
+const mergedConfig = createConfig('jest', {
   setupFilesAfterEnv: [
     'jest-expect-message',
     '<rootDir>/src/setupTest.js',
@@ -16,6 +16,24 @@ module.exports = createConfig('jest', {
     // This alias is used for plugins in the plugins/ folder only.
     '^CourseAuthoring/(.*)$': '<rootDir>/src/$1',
   },
-  modulePathIgnorePatterns: [
-  ],
+  modulePathIgnorePatterns: [],
 });
+
+// Override ts-jest config: When transforming .ts files to .js for test purposes,
+// don't report TypeScript errors for files in `node_modules/` (or any non-test files).
+// Without this, we were seeing TypeScript errors from
+//   node_modules/@edx/frontend-component-header/dist/studio-header/StudioHeader.tsx
+// cause the tests to fail, because they are included in `transformIgnorePatterns`.
+// -> If you can delete the following lines and the tests still pass, then feel free
+//    to remove this whole override. It's only necessary now while StudioHeader has some
+//    typing issues.
+mergedConfig.transform['^.+\\.[tj]sx?$'] = [
+  'ts-jest',
+  {
+    diagnostics: {
+      exclude: ['!**/*.test.*'],
+    },
+  },
+];
+
+module.exports = mergedConfig;