Proof of concept test migration -- client > utils > getConfig

[clairep94]

Proof of concept for starting to migrate the client folder

Context:

• Experimentation with starting to migrate the client folder to typescript and to set up automatic typescript checking

• Starts to address work required in Month 1 and some of the challenges described in my proposal:

  • Installing dependencies required for Typescript & any peer-dependency bumps
  • Preventing silent regression by adding unit tests
  • Avoiding assumptions about input/output types when migrating
  • Adding tooling to automate checking for typescript errors

• Chose to migrate utils/getConfig as the instance of a node file for Month 1 as this file had an associated unit test and the useage throughout the repo was relatively straightforward

• I have a second PR that starts to migrate client/common/ButtonOrLink here which is separated from this PR for clarity

Changes

• Installed typescript and typescript related deps/types for babel, node, react
• Set up TSConfig in the root, which points to a TSConfig in the client (server will be added later)
• Update webpack, babel and eslint configs to be able to parse .ts and .tsx files
  • Tried to add @typescript-eslint/parser and @typescript-eslint but got blocked due to eslint version peer-dependency
• Add a package.json script typecheck:client to check for typescript errors on client files
• Updated the husky pre-commit to use this
• Added a test:watch script for easier unit test-writing
• Migrated and re-factored client/utils/getConfig & updated unit tests
  • Checked all instances of useage in the repo and addressed each of the use-cases (input & output expected types)
  • Updated the isTestEnvironment() function to prevent circularity
  • Updated getConfig() to take an options object param that includes indicating whether it should output nullish strings ('') and/or output a desired type, such as a number
    • See tests for details. I have put examples of use-cases in the test comments
• Update each file that calls getConfig()

Screenshots:

1. Looking for instances of getConfig() useage

2. Example of instance where the nullish value expected should be `''` instead of `undefined` --> in this file, it would result in `'undefined'` if this update to `getConfig()` was not made
3. Example of instance where nullish value expectd should be `undefined` -- getConfig can handle this as default