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Add component-no-value exception #38

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Add component-no-value exception #38

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28 changes: 22 additions & 6 deletions src/darkleaf/di/core.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -92,11 +92,12 @@
:declared-deps deps
:remaining-deps (seq deps)}))

(defn- build-obj [built-map head]
(defn- build-obj [built-map head stack]
(let [factory (:factory head)
declared-deps (:declared-deps head)
built-deps (select-keys built-map (keys declared-deps))]
(p/build factory built-deps)))
(p/build factory
(with-meta built-deps {::build-stack stack}))))

(defn- build [{:keys [registry *stop-list]} key]
(loop [stack (list (stack-frame key :required (registry key)))
Expand Down Expand Up @@ -126,7 +127,7 @@
built-map))

:else
(let [obj (build-obj built-map head)
(let [obj (build-obj built-map head stack)
stop #(p/demolish factory obj)]
(vswap! *stop-list conj stop)
(case [obj dep-type]
Expand Down Expand Up @@ -592,12 +593,25 @@
(defn- stop-fn [variable]
(-> variable meta (::stop (fn no-op [_]))))

(defn- no-value-component! [stack]
(let [key (-> stack peek :key)]
(throw (ex-info (str "Component returned no value " key)
{:type ::component-no-value
:stack (map :key stack)}))))

(defn- ensure-component-result! [result stack]
(if (nil? result)
(no-value-component! stack)
result))

(defn- var->0-component [variable]
(let [stop (stop-fn variable)]
(reify p/Factory
(dependencies [_])
(build [_ _]
(variable))
(build [_ empty-deps]
(ensure-component-result!
(variable)
(::build-stack (meta empty-deps))))
(demolish [_ obj]
(stop obj)))))

Expand All @@ -608,7 +622,9 @@
(dependencies [_]
deps)
(build [_ deps]
(variable deps))
(ensure-component-result!
(variable deps)
(::build-stack (meta deps))))
(demolish [_ obj]
(stop obj)))))

Expand Down
15 changes: 15 additions & 0 deletions test/darkleaf/di/dependencies_test.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,21 @@
(try-ex-data (di/start `parent)))))


(defn ^{::di/kind :component} component-no-value
[])


(defn parent-2
[{::syms [component-no-value]}]
:done)


(t/deftest component-no-value-exception-test
(t/is (= {:type ::di/component-no-value
:stack [`component-no-value `parent-2 ::di/implicit-root]}
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You don’t need the stack here. You can identIfy an invalid component just by its key

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@KGOH KGOH Dec 6, 2024 •
edited
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While just a key is enough to identify the component, it may not be enough in a case when a component returns nil, but I didn't expect this component to be executed at all. In such case it may be obvious why the component returns nil, but it would be not clear at all why this component was used at all in a such configuration

Though, we can omit the stack and wait when we stumble upon a such case where a stack would be helpful to see

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There seem to be two issues. The first is a notification about invalid component.
The second is about adding extra info such a stack of components.

You can solve the second with the following pattern:

(try
  (...)
  (catch RuntimeException ex
    (throw (ex-info "..." {:stack stack} ex))))

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@KGOH KGOH Dec 6, 2024 •
edited
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Good idea!
@slaughtlaught ^^^

(try-ex-data (di/start `parent-2)))))


(defn recursion-a
[{::syms [recursion-b]}]
:done)
Expand Down
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