When working with third-party services, one is more likely than not to end up parsing a JSON document. For well-behaved APIs, documentation and examples are available, so the job usually becomes some minor variation of:
- Reach for the "canonical" JSON parsing library in your language
- Grab some example JSON and do some ad-hoc parsing of the bits you're interested in,
- Maybe write a class/type/module/namespace to immortalize adapting said JSON data to your domain, hopefully with accompanying tests.
- Think everything is okay, until some live data comes in with missing keys (or extra keys!) inconsistent types (nulls where they promised they wouldn't show up, invalid date formats, etc.)
- Go back to step 2 with the newfound edge cases, adapt.
Sometimes it's a quick process: couple of caveats you missed in the documentation, sometimes it's painstaking; the ability to close the loop in a fast, but robust, manner becomes invaluable: you don't want to spend days, and a lot of boilerplate, only to discover that some deep details didn't really work out. I believe a good type system and a good parser help a lot, but the last mile is all about the "getting to the bits of data relevant to your domain." Optics are my tool of choice for that.