Design

Goal

The Goal is to learn to use the Json.Decode and Json.Encode modules.

Learning objectives

Students should be able to

encode any JSON Value (Json.Encode.object, list and other primitives)
prettify a value (encode)
understand why decoders are useful even though the concept is unusual
decode JSON primitives (bool, int, string, null...)
decode data structures (list, dict, nullable)
decode objects (field)
deal with uncertainty (maybe, oneOf)
modify and chain decoders (map, andThen, succeed, fail)
run a decoder on a string input (decodeString)

Out of scope

encoder aliases (array, set)
more niche decoders (array, keyValuePairs, oneOrMore, index, at, value)
dealing with Error specifics
decoding recursive structures (lazy, a quick mention is fine)

Concepts

The concept this exercise unlocks is:

json

Prerequisites

strings
lists
tuples
dict
records
maybe
custom-types
pattern matching

Analyzer

Make sure that

decodeUser uses decodeId and decodeName
decodeComment uses decodeId, decodePullRequestReviewId, decodeUser, decodeSide, decodeLinks
decodeComments uses decodeComment