Add election api typescript

[kodikos]

What?

This is restoring the typescript port of the election api test that Rossano did. With some tweaks to freshen it.

Why?

We're appearing a bit dated when we give users pure JS tests. In some cases, we specifically want to assess their typescript abilities, and this hasn't been possible with these standard tests.

[iuketaylor]

copied from slack convo

The TS code looks good, as an MVP could probably get away with just updating the TS/node/dependency versions and verifying the tests still work

Everything i'd probably change to modernise it:

• Node 18 EOL - move to LTS
• TS 5.1.3 - move to 7.0.2 (probably restricting candidates if we stay on 5)
• Express/other deps need updating
• Replace jest with vitest (nightmare to work with TS)
• replace ts-node/ts-node-dev with tsx
• convert from commonJS to ESM
• Update readme instructions to install latest stuff
• Update any links referencing old js files

[iuketaylor]

Mostly looks really good 🙌

I think we'll need to change the validation logic and also add some config options to the tsconfig though

[iuketaylor]

I don't think this validation is correct, just a couple of things:

1. We should be asserting on id, name, seqNo, and partyResults rather than candidate, and votes
2. To do it the "TypeScript way" you'd want to use a type predicate eg (...): value is Result (see examples below), this will make sure the type is narrowed and correct at runtime
3. A weird JS/TS quirk: typeof resultCandidate !== "object" - this isn't enough unfortunately because JS is strange it also thinks null and Arrays can be typeof "object" so to be "correct" we'd need to handle those more explicitly eg:

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

What I think the validation would look like if we wanted to match the Java version:

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

function validatePartyResult(value: unknown): value is PartyResult {
  if (!isRecord(value)) return false;

  return (
    typeof value.party === "string" &&
    typeof value.votes === "number" &&
    typeof value.share === "number"
  );
}

function validateResult(value: unknown): value is Result {
  if (!isRecord(value)) return false;

  return (
    typeof value.id === "number" &&
    typeof value.name === "string" &&
    typeof value.seqNo === "number" &&
    Array.isArray(value.partyResults) &&
    value.partyResults.every(validatePartyResult)
  );
}

[iuketaylor]

We'll need to add "rootDir" here cos TypeScript 7 requires it when we implement the comment below

Suggested change

	"outDir": "./dist",
	"outDir": "./dist",
	"rootDir": "./src"

[iuketaylor]

We'll need to restrict what TypeScript builds, currently everything is being build which means Vitest is discovering both the source and the built files and running the tests twice resulting in the tests duplicated.

Before:

 ✓ dist/test/scoreboard.spec.js (4 tests) 894ms
     ✓ first 554  331ms
     ✓ test all results  460ms
 ✓ test/scoreboard.spec.ts (4 tests) 898ms
     ✓ first 554  330ms
     ✓ test all results  463ms

 Test Files  2 passed (2)
      Tests  8 passed (8)
   Start at  11:16:09
   Duration  1.18s (transform 75ms, setup 0ms, import 361ms, tests 1.79s, environment 0ms)

After:

✓ test/scoreboard.spec.ts (4 tests) 943ms
   ✓ Scoreboard Tests (4)
     ✓ first 5 24ms
     ✓ first 100 77ms
     ✓ first 554  364ms
     ✓ test all results  475ms

 Test Files  1 passed (1)
      Tests  4 passed (4)
   Start at  11:17:09
   Duration  1.16s (transform 28ms, setup 0ms, import 117ms, tests 943ms, environment 0ms)

Suggested change

	}
	},
	"include": ["src/**/*.ts"],
	"exclude": ["dist", "node_modules"]

[iuketaylor]

Minor one but probably makes sense to align the Node types with the Node version 24 we're using