Clarify how devDependencies should be used for NPM packages (OEP-67: Standard Tools and Technologies)

[bradenmacdonald]

Per a discussion with @regisb about how we can speed up MFE build times in Tutor, I want to clarify how dependencies and devDependencies should be used. The goal is that tutor can install MFE dependencies using npm ci --production which would do a fast install that excludes devDependencies. This will be a significant speedup in the case where we can exclude things like Jest (which is a very large and bloated package¹) that aren't needed just to build and deploy the MFE.

Note: this is very much not the case now:

• frontend-build includes Jest, eslint, TypeScript, react-dev-utils, and more in dependencies, and puts @babel/preset-typescript which I think is required for build in devDependencies
• course-authoring MFE puts frontend-build and axios as devDependencies
• The learning MFE puts frontend-build as a devDependency
• The learner-dashboard MFE puts jest, @testing-library/user-event, and redux-devtools-extension as dependencies while putting @openedx/frontend-build as a devDependency

Footnotes

1. npx howfat jest says 487 deps, 49.6mb ↩

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[davidjoy]

We talked briefly in Slack about how frontend-build's dependencies are a special case within that package, but I think this is more than accurate for our libraries and MFEs. Looks good!

[feanil]

Makes sense and this is how we operate by default with the backend dependencies.

[brian-smith-tcril]

👍

[xitij2000]

I don't know how typescript is configured here, but I've had it throw errors at build time if types aren't available. Would that be a problem here?

[bradenmacdonald]

Good point, and I'll have to check how we're doing the build. But normally to keep builds fast, the type checking is done using tsc during the same time when we run the test suite / linter / code formatter / etc., and the build process uses a much faster process to merely strip out the TypeScript annotations without actually parsing them. After all, you don't need to run the linter nor the test suite during the build so neither do you need to type check.

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