Include has_many through: relationship fails

With the following set of models:

class User < ActiveRecord::Base
    ...
    has_many :participations
    has_many :attempts, through: :participations
    has_many :completed_attempts, -> { completed }, through: :participations, source: :attempts
    ...
end

class Participation < ActiveRecord::Base
    ...
    belongs_to :user
    has_many :attempts
    ...
end

class Attempt < ActiveRecord::Base
    ...
    belongs_to :participation
    ...
end

the request GET /users/1?include=completed-attempts fails. completed-attempts.txt.

Likewise, GET /users/1?include=completed-attempts,attempts fails. completed-attempts_attempts.txt

However, as expected, GET /users/1?include=attempts works. attempts.txt

Changing the order, GET /users/1?include=attempts,completed-attempts, doesn't fail with a 500, however it returns the full list of Attempts for both the attempts and completed-attempts relationships. attempts_completed-attempts.txt

Querying the relations directly from the AR object works correctly for both attempts and completed_attempts.

首先，使用 User、Participation 和 Attempt 模型定义重现列出的 GET /users/1 请求，并将 include 响应与直接的 ActiveRecord 查询进行比较。调查经过筛选的 has_many-through 关系的处理方式以及嵌套 include 的顺序；当 completed-attempts 仅返回已完成的 Attempt，且所有列出的请求都避免 500 时，即视为完成。