global ex-handler enabled

README.md

@@ -45,7 +45,20 @@ If a value is not present in data, its value pulled will be `:robertluo.pullable
 
 If a value is a function, you can pass `:with` arguments, it will apply these arguments to the function and return it.
 
+### `:batch` option
+
+If you want to call `:with` multiple times, `:batch` option will return a sequence of calling returning value also in a sequence.
+
+## Error Handling
+
+When an exception raised when pulling a key, the corresponding value will be an error map like:
+
+`{:error/key :key-of-error, :error/message "the exception message", :error/data {...}}`
+
+You can provide an global exception handler function which will receive this error map as the argument, and the return value will be the value instead. A common practice might be logging.
+
+
 ## License
 Copyright © 2020 Robertluo
 
-Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.
+Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.

src/robertluo/pullable.clj

@@ -30,6 +30,10 @@
    `:seq` option also can specific offset and limit. e.g. `:seq [10 20]` means pulling
    from the collection starting from index 10 (0 based), and take 20.
    "
-  [data ptn]
-  (when-let [q (some-> (ptn/pattern->query ptn) core/query)]
-    (core/-select q data)))
+  ([data ptn]
+   (pull data ptn nil))
+  ([data ptn ex-handler]
+   (when-let [q (some-> (ptn/pattern->query ptn)
+                        (assoc :ex-handler ex-handler)
+                        core/query)]
+     (core/-select q data))))

src/robertluo/pullable/core.clj

@@ -131,11 +131,12 @@
   [::batch (BatchProcessor. calls)])
 
 (defn query
-  [qspec]
+  [{:keys [options children ex-handler] :as qspec}]
   (map->CoreQuery (assoc qspec
-                         :children (->> (:children qspec)
-                                        (map query))
-                         :processors (->> (:options qspec)
+                         :children (cond->> children
+                                     ex-handler (map #(assoc % :ex-handler ex-handler))
+                                     true       (map query))
+                         :processors (->> options
                                           (cons [::core (CoreProcessor.)])
                                           (map option-create)
                                           (into (array-map))

test/robertluo/pullable_test.clj

@@ -44,4 +44,7 @@
              (sut/pull data '(:fn2 :with [7])))))
     (testing ":batch option will batch :with calls"
       (is (= {:fn2 [{:val 8} {:val 9}]}
-             (sut/pull data '(:fn2 :batch [[7] [8]])))))))
+             (sut/pull data '(:fn2 :batch [[7] [8]])))))
+    (testing "global error handler option allow you to handle exceptions"
+      (is (= {:fn2 :fn2}
+             (sut/pull data '(:fn2 :with ["ok"]) :error/key))))))