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SyntaxError: Unexpected token 'export'

Not confirmed yet · posted Oct 28

Cause

Jest runs tests as CommonJS and its default transformIgnorePatterns skips node_modules, so an ESM-only dependency reaches the CommonJS loader untranspiled.

Fix

risk: low

// jest.config.js: let the transformer compile the ESM-only packagestransformIgnorePatterns: ['/node_modules/(?!(<esm-pkg>|@scope/<pkg>)/)'],// pnpm layout: '<rootDir>/node_modules/.pnpm/(?!(<esm-pkg>|@scope\\+<pkg>)@)'// babel-jest: presets must live in babel.config.js (.babelrc never applies in node_modules)// ts-jest: use createJsWithTsPreset() with allowJs so .js files are compiled too

Don’t try

keep the Babel presets in .babelrc and only widen transformIgnorePatterns — .babelrc applies only inside its own package, so files under node_modules are transformed with no presets and still contain export.

one transformIgnorePatterns entry per package — a path is skipped if it matches any pattern, so each entry's negative lookahead re-ignores the other packages; combine them in one regex.