Restore the JavaScript test suite - #499

Summary

npm test — which make test and CI both run — cannot start. Three separate problems, all introduced when the JS dependencies were bumped:

1. ava rejects its own config

$ npx ava
× Unexpected Babel configuration for AVA. See https://github.com/avajs/ava/blob/v2.3.0/docs/recipes/babel.md for allowed values.

ava 2 only accepts extensions and testOptions under the babel key. babel-register already reads .babelrc on its own, so the key is redundant and is simply dropped.

2. The test script passes a directory

$ npx ava src/javascript/tests
× src/javascript/tests is not a test file.

ava 2 resolves CLI arguments as literal paths. Its default file patterns already include **/*.spec.js, and every file under src/javascript/tests/ is one, so the argument is not needed.

3. The default import of erlang-types is undefined under babel 6

node_modules/erlang-types/lib/index.js sets __esModule and exports only named bindings, so _interopRequireDefault returns the module unchanged and .default is undefined:

import ErlangTypes from 'erlang-types';   // undefined
const selfPID = new ErlangTypes.PID();    // TypeError

which made every spec fail:

Uncaught exception in src/javascript/tests/for.spec.js
  TypeError: Cannot read properties of undefined (reading 'PID')

The rollup build tolerates the default import because rollup-plugin-commonjs maps a CJS module without a default export onto the namespace object, but a namespace import is the correct form for both toolchains.

Changes

• package.json: drop the invalid ava.babel key, change test to nyc ava
• core.js, core/erlang_compat/{erlang,lists,maps}.js: use import * as ErlangTypes from 'erlang-types'

Testing

With these changes:

$ npx ava
  71 tests passed

npm run build still succeeds, and the regenerated priv/testrunner/vendor.build.js is byte-identical to the committed one.

Note on npm test itself: it could not be run end-to-end here. nyc ava aborts with Cannot find module '...\node' because nyc 14 predates the Node version used for this check (the project pins Node 12.8.1 in .travis.yml). nyc is untouched by this PR, which is why the run above uses npx ava directly.