Fix: Import Babel config from package.json and export in babel.config.js to fix Jest tests in custom plugins that have a package.json

[dancastellon]

Resolves #4781
Impact: minor
Type: bugfix

Issue

Babel 7 doesn't transpile files in sub-directories that have a package.json when Babel is configured through package.json or .babelrc. This causes Jest test failures in custom plugins that have a package.json. It isn't an issue with non-test files because those are imported through the main Reaction app (see /server/plugins.js and client/plugins.js). Babel does transpile these files when it is configured through the new babel.config.js. Meteor currently only loads Babel config through .babelrc or package.json, though.

Solution

Meteor only reads the babel config from .babelrc or package.json. So with just babel.config.js, the Meteor app fails but the Jest tests pass. With just package.json, the Jest tests in custom plugins fail but the app runs.

In order to support Babel transpiling of Jest tests, we load the babel config defined in package.json and export it in the new babel.config.js.

Breaking changes

None

Testing

1. Create a folder inside imports/plugins/custom
2. In the folder, run npm init and create an empty package.json
3. Create a file named log.js with console.log("test"); in it
4. Create a log.test.js file with the following content:

import "./log";
test("Simple test", () => { expect(true).toBe(true); });

4. Back in the reaction root dir, run meteor npm run test:unit
5. Confirm "Simple test" passes

[spencern]

@dancastellon What were the reasons you decided to read in the existing package.json babel section rather than just moving the babel config? Is it dynamically configured right now?

[dancastellon]

@spencern Meteor only reads the babel config from .babelrc or package.json. So with just babel.config.js, the Meteor app fails but the Jest tests pass. With just package.json, the Jest tests in custom plugins fail but the app runs.

[spencern]

Would like to note the Meteor dependency on keeping the babel configuration within Package.json in the code. Looks good otherwise.

[spencern]

I'd like to add a note here mentioning that this is required because as you mentioned

Meteor only reads the babel config from .babelrc or package.json. So with just babel.config.js, the Meteor app fails but the Jest tests pass. With just package.json, the Jest tests in custom plugins fail but the app runs.

So that we're aware of why we did this and if Meteor changes or our dependency on Meteor changes we can change this in the future.

[dancastellon]

@spencern Comment added

[spencern]

👍