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Allow to return nil from a defn of a component #64

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Merged
darkleaf merged 1 commit into from
Nov 7, 2025
Merged

Allow to return nil from a defn of a component #64

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12 changes: 2 additions & 10 deletions src/darkleaf/di/core.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -651,19 +651,12 @@
(defn- stop-fn [variable]
(-> variable meta (::stop (fn no-op [_]))))

(defn- validate-obj! [obj variable]
(when (nil? obj)
(throw (ex-info "A component fn must not return nil"
{:type ::nil-return
:variable variable}))))

(defn- var->0-component [variable]
(let [stop (stop-fn variable)]
(reify p/Factory
(dependencies [_])
(build [_ _ add-stop]
(let [obj (variable)]
(validate-obj! obj variable)
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@KGOH KGOH Nov 7, 2025

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а в чём вообще была проблема из-за которой появился запрет на возврат буквального nil из компонента?

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@darkleaf darkleaf Nov 7, 2025 •
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Собранный компонент - это значение.
Когда функа использует компонент, он может быть required или optional, это объявляется через :or в дестракчеринге.
Если компонент nil - то в процессе запуска об этом будет ошибка.

Тот факт, что в миграциях у нас может быть nil из-за when - это прикол нашего проекта.
Попробую через middleware в проекте поправить, посмотрим как приживется

тут наверное проблема в том, что в clojure смешивается nil и undefined

(let [obj (?? (variable) ::nil)]
(add-stop #(stop obj))
obj))
(description [_]
Expand All @@ -676,8 +669,7 @@
(dependencies [_]
deps)
(build [_ deps add-stop]
(let [obj (variable deps)]
(validate-obj! obj variable)
(let [obj (?? (variable deps) ::nil)]
(add-stop #(stop obj))
obj))
(description [_]
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8 changes: 4 additions & 4 deletions test/darkleaf/di/component_test.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -15,12 +15,12 @@
nil)

(t/deftest nil-component-0-arity-test
(let [ex (catch-some (di/start `nil-component-0-arity))]
(t/is (= ::di/nil-return (-> ex ex-cause ex-data :type)))))
(let [root (di/start `nil-component-0-arity)]
(t/is (= ::di/nil @root))))

(t/deftest nil-component-1-arity-test
(let [ex (catch-some (di/start `nil-component-1-arity))]
(t/is (= ::di/nil-return (-> ex ex-cause ex-data :type)))))
(let [root (di/start `nil-component-1-arity)]
(t/is (= ::di/nil @root))))


(defn component-2-arity
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