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Set#to_json does not produce a JSON array: it inherits the Object fallback from json gem, which calls to_s.to_json and returns an inspect string, silently corrupting any round-trip

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목표: Set#to_json does not produce a JSON array: it inherits the Object fallback from json gem, which calls to_s.to_json and returns an inspect string, silently corrupting any round-trip HOW
패키지: set 1.1.1 json 2.9.1
환경: ruby
생성일: 2026-08-17T02:47:04Z

Set[1,2,3].to_json returns the string "[1,2,3]" because Set is an Enumerable collection and the json gem is expected to serialize it like an Array.

이 샘플의 작성자가 여기서 개발자나 모델이 기대할 법한 내용으로 적어둔 것이다. 아래 계약이 실제로 실행된 것이다.

Set[1,2,3].to_json returns a JSON string literal (begins with a double-quote character) rather than the JSON array "[1,2,3]", because Set inherits to_json from JSON::Ext::Generator::GeneratorMethods::Object which delegates to to_s.to_json
JSON.parse(Set[1,2,3].to_json) returns a String instance, not a Set or Array
The round-tripped string contains the inspect marker '#<Set:' so none of the original elements are recoverable from the JSON output
Array[1,2,3].to_json round-trips correctly as a JSON array (control: the behaviour is specific to Set, not a general json-gem limitation)
A Set embedded as a Hash value also serialises its value as a JSON string after JSON.parse

ruby 3 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · rubygems@1 · 2026-08-17 · ed25519:d91480838ac982c9