Component validation

src/darkleaf/di/core.clj

@@ -92,12 +92,22 @@
      :declared-deps  deps
      :remaining-deps (seq deps)}))
 
-(defn- build-obj [built-map head]
-  (let [factory       (:factory head)
+(defn- build-obj* [built-map stack]
+  (let [head          (peek stack)
+        factory       (:factory head)
         declared-deps (:declared-deps head)
         built-deps    (select-keys built-map (keys declared-deps))]
     (p/build factory built-deps)))
 
+(defn- build-obj [built-map stack]
+  (try
+    (build-obj* built-map stack)
+    (catch RuntimeException ex
+      (throw (ex-info "An error during component build"
+                      {:type  ::build-obj-fail
+                       :stack (map :key stack)}
+                      ex)))))
+
 (defn- build [{:keys [registry *stop-list]} key]
   (loop [stack     (list (stack-frame key :required (registry key)))
          built-map {}]
@@ -126,7 +136,7 @@
                    built-map))
 
           :else
-          (let [obj  (build-obj built-map head)
+          (let [obj  (build-obj built-map stack)
                 stop #(p/demolish factory obj)]
             (vswap! *stop-list conj stop)
             (case [obj dep-type]
@@ -592,12 +602,19 @@
 (defn- stop-fn [variable]
   (-> variable meta (::stop (fn no-op [_]))))
 
+(defn- check-nil-value-component! [component var]
+  (if (nil? component)
+    (throw (ex-info (str "Component returned nil value" var)
+                    {:type ::nil-value-component}))
+    component))
+
 (defn- var->0-component [variable]
   (let [stop (stop-fn variable)]
     (reify p/Factory
       (dependencies [_])
       (build [_ _]
-        (variable))
+        (-> (variable)
+            (check-nil-value-component! variable)))
       (demolish [_ obj]
         (stop obj)))))
 
@@ -608,7 +625,8 @@
       (dependencies [_]
         deps)
       (build [_ deps]
-        (variable deps))
+        (-> (variable deps)
+            (check-nil-value-component! variable)))
       (demolish [_ obj]
         (stop obj)))))
 

test/darkleaf/di/component_test.clj

@@ -0,0 +1,34 @@
+(ns darkleaf.di.component-test
+  (:require
+   [clojure.test :as t]
+   [darkleaf.di.core :as di])
+  (:import
+   (clojure.lang ExceptionInfo)))
+
+(defmacro catch-cause-data [& body]
+  `(try ~@body
+        (catch clojure.lang.ExceptionInfo e#
+          (->> e#
+               Throwable->map
+               :via
+               (mapv :data)))))
+
+(defn nil-value-component
+  {::di/kind :component}
+  []
+  nil)
+
+(defn nil-value-component-1-arity
+  {::di/kind :component}
+  [_]
+  nil)
+
+(t/deftest nil-value-component-test
+  (t/is (= [{:type  ::di/build-obj-fail
+             :stack [`nil-value-component ::di/implicit-root]}
+            {:type ::di/nil-value-component}]
+           (catch-cause-data (di/start `nil-value-component))))
+  (t/is (= [{:type  ::di/build-obj-fail
+             :stack [`nil-value-component-1-arity ::di/implicit-root]}
+            {:type ::di/nil-value-component}]
+           (catch-cause-data (di/start `nil-value-component-1-arity)))))

test/darkleaf/di/tutorial/x_ns_publics_test.clj

@@ -4,7 +4,7 @@
    [darkleaf.di.core :as di]))
 
 ;; excluded
-(def nil-component nil)
+(def nil-value-component nil)
 
 ;; excluded
 (def unbound-component)

test/darkleaf/di/tutorial/y_graceful_stop_test.clj

@@ -13,6 +13,11 @@
 ;; It throws with original exception.
 ;; All other possible exceptions are added as suppressed.
 
+(defn ex-map-wo-via [ex]
+  (-> ex
+      Throwable->map
+      (dissoc :via)))
+
 (defn root
   {::di/kind :component}
   [{dep              `dep
@@ -34,5 +39,5 @@
                            (di/start `root registry)
                            (catch Throwable ex
                              ex))]
-    (t/is (= on-start-root-ex ex))
+    (t/is (= (ex-map-wo-via on-start-root-ex) (ex-map-wo-via ex)))
     (t/is (= [on-stop-dep-ex] (vec (.getSuppressed ex))))))