TSM-04: convert core entry and shared infra to TypeScript

[Justin Hammond (Justintime50)]

Summary

• rename core entry and shared modules to TypeScript: easypost, constants, util, internal_util
• update Vite library entry to src/easypost.ts and resolve extensions for .ts + .js
• keep runtime behavior unchanged while migration proceeds with temporary ts-nocheck on converted files
• allow permissive incremental migration in source typecheck by setting noImplicitAny=false in tsconfig.build.json

Validation

• npm run typescript
• npm run build
• npx eslint src/easypost.ts src/constants.ts src/utils/util.ts src/utils/internal_util.ts
• npx vitest run test/services/module_exports_compat.test.js

[Alex Matthews (ralexmatthews)]

Nice, mostly looks good. I would just strongly suggest keeping noImplicitAny disabled here.

Would also suggest stronger types on the client options, but that one is nonblocking.

[Alex Matthews (ralexmatthews)]

Question:
Hmmm... are these just stubs for later, or are these actually anything? For example, httpClient could now be initialized with 2 and it would be valid according to TS.

Ideally we would type these with what we expect. For example, httpClient: typeof fetch or similar.

[Alex Matthews (ralexmatthews)]

Suggestion:
I would strongly argue to keep this enabled. This can very easily allow type errors to get swept under the rug. If you create a new function, this no longer requires that function's parameters to be typed.

const getFooBar = (arg) => arg.foo.bar;
// ...
getFooBar("abc")

now compiles fine, even though this will be a runtime error.