Monorepo with babel aliases support

[yuriy-yarosh]

I'm using ava with babel-preset-typescript and a set of path aliases for monorepo, e.g. @org/testing-common/src/Common.ts to testing-common/Common.ts aliasing.

ava.config.cjs

module.exports = {
  files: [
    './test/**/*Test.ts',
  ],
  require: [
    '@org/config-testing/Register.js',
  ],
  snapshotDir: 'test/snapshots',
  concurrency: 64,
  failFast: true,
  failWithoutAssertions: false,
  verbose: true,
  nodeArguments: [
    '--trace-deprecation',
  ],
  nodeArguments: [
    '--experimental-modules'
  ],
  extensions: ['ts', 'tsx', 'mts']
};

Both @ava/typescript and plain babel register results with the same error.

Register.js

const babelRC = require('./.babelrc.js');

require('@babel/register')({
  extensions: ['.es6', '.es', '.jsx', '.js', '.mjs', '.ts', 'tsx', '.mts'],
  cache: false,
  ...babelRC,
});

.babelrc with a custom expo preset and an alias resolver.

const { production } = require('@org/config-babel-preset-expo/Resolver.js')

module.exports = {
  "env": {
    "coverage": {
      "plugins": ["istanbul"]
    }
  },
  "presets": [
    "@babel/preset-typescript",
    "@org/config-babel-preset-expo",
    ["@babel/preset-env", {
      "forceAllTransforms": false,
      "modules": "auto",
      "targets": production
    }],
    ["@babel/preset-react", {
      "runtime": "automatic",
    }],
  ],
  "plugins": [
    "babel-plugin-transform-typescript-metadata",
    "macros",
    ["@babel/plugin-proposal-decorators", { "legacy": true }],
    ["@babel/plugin-proposal-class-properties", { "loose": true  }]
  ]
}

With aliased imports for tests

import { hasDir, isFile } from 'config-testing-common/Common';

I'm always getting

 export * from 'config-testing-common/Mocked';
  ^^^^^^

  SyntaxError: Unexpected token 'export'

But relative imports for my ava test files work just fine

import { hasDir, isFile } from '../src/Common';

Everything else everywhere is aliased.

My ava config doesn't work without a custom @babel/register - using @ava/typescript config only gives

SyntaxError: Cannot use import statement outside a module

[yuriy-yarosh]

At least I've noticed that aliased imports are working correctly only for the current package.
I can't import anything across yarn workspace without prior compilation with babel and the respective path rewriting, which is puzzling.

Maybe ava.js has something similar to get-package-type somewhere, similarly to tape, so the respective rewrites module aliases could be forced with a custom config there (e.g. to specify explicitly that an alias is a module).

[novemberborn]

You can do that by file type: https://github.com/avajs/ava/blob/main/docs/06-configuration.md#configuring-module-formats

All these loaders make things very complicated. AVA does the right thing with require() or import() when loading your test file, and from there on the test file controls how things are loaded. My advice is to compile to disk and rewrite the import, which is what @ava/typescript does.

[yuriy-yarosh]

@novemberborn right now, the only way to make ava work with TypeScript this way (on Node 20), is to use TSX loader via NODE_OPTIONS='--import tsx' yarn ava.

The ts-node/esm loader import via NODE_OPTIONS as NODE_OPTIONS='--import ts-node/esm yarn ava, hangs up completely, for unknown reason.

It would be great if someone could figure something out with ts-node.
tsx has wayyy too many limitations e.g. no decorators support for TypeORM / MikroORM in esbuild evanw/esbuild#104
I'd rather use swc instead of esbuild there.

[novemberborn]

This is why @ava/typescript exists — it avoids the entire mess by having the compiler be external to AVA.