submap? - 递归检查一个映射是否包含另一个映射

Question

(submap? m1 m2) 递归检查 m1 是否包含在 m2 中

用法

(deftest submap
  (is (submap? {} {}))
  (is (not (submap? {:k 1} {})))
  (is (submap? {:k 1} {:k 1 :j 2}))
  (is (submap? {:k {:kk 1}} {:k {:kk 1 :j 2}}))
  (is (not (submap? {:k {:kk 1}} {:j 2}))))

这种需求常出现在测试中，你想要检查经测试的函数返回的映射是否有某种形状，并且假定一个开放的世界，即你想忽略任何额外的键，这样修改函数测试就不会破坏测试。

;; BAD: doesn't assume open world
(is (= {:k :v} (function-under-test)))

;; BAD: not expressive
(is (= :v (:k (function-under-test))))

;; BAD: not expressive, need to write :k twice
(is (= {:k :v} (select-keys (function-under-test) [:k])))

;; GOOD: expressive
(is (submap? {:k :v} (function-under-test)))

许多代码库中已经存在实现（GitHub 代码搜索中有 400+ 次）。示例

https://github.com/clojure/tools.deps/blob/ecc80420c1b734b384f7a42df91684cdbc37ddc6/src/test/clojure/clojure/tools/deps/util.clj#LL12-L25C18

https://github.com/ptaoussanis/encore/blob/96547700c03a5e81d784bcc9253980d7355f2f2b/src/taoensso/encore.cljc#L2071

Answer 1

作为 https://clojure.atlassian.net/browse/CLJ-2755 登录