From a4297f3c58c77ab7109c77831ca81bbfe30f168d Mon Sep 17 00:00:00 2001
From: Ursa Americanus Kermodei <venantius@gmail.com>
Date: Thu, 16 Jul 2015 23:16:48 -0700
Subject: [PATCH] [bugfix] Fixing a ClassNotFoundException

Resolves #30.

This fixes a problem where a var that looked like a Java class
constructor would cause Yagni to try to resolve the class it thought
existed. Unfortunately, while `resolve` returns nil when it believes
it's dealing with a Clojure symbol, when it's targeting something it
believes to be a Java class it throws a ClassNotFoundException.

This commit wraps the resolve attempt in a try/catch block - it's ugly,
but I'm not aware of a more elegant solution at the moment.
---
 src/yagni/jvm.clj       | 14 +++++++++++---
 test/yagni/jvm_test.clj |  6 ++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/yagni/jvm.clj b/src/yagni/jvm.clj
index 442720e..269494e 100644
--- a/src/yagni/jvm.clj
+++ b/src/yagni/jvm.clj
@@ -1,6 +1,7 @@
 (ns yagni.jvm
   "Utility functions for working with the JVM."
-  (:require [clojure.string :as string]))
+  (:require [clojure.reflect :refer [resolve-class]]
+            [clojure.string :as string]))
 
 (defn class-name->var-name
   "Return the var name for the given class name.
@@ -29,6 +30,13 @@
         c (last v)]
     (symbol (string/join "." [n c]))))
 
+(defn can-resolve-class?
+  [c]
+  (try
+    (resolve c)
+    (catch ClassNotFoundException e
+      false)))
+
 (defn is-class-generator?
   "Check to see if a given var is a class generator. If it is, returns the
    Java class for the generator in question.
@@ -42,10 +50,10 @@
     (or
      (and
       (.startsWith name "->")
-      (resolve (var-name->class-name (symbol n (subs name 2)))))
+      (can-resolve-class? (var-name->class-name (symbol n (subs name 2)))))
      (and
       (.startsWith name "map->")
-      (resolve (var-name->class-name (symbol n (subs name 5))))))))
+      (can-resolve-class? (var-name->class-name (symbol n (subs name 5))))))))
 
 (defn is-class-constructor?
   "Check to see if a given symbol is a class constructor (e.g. `(String.)`)"
diff --git a/test/yagni/jvm_test.clj b/test/yagni/jvm_test.clj
index 7bef181..29c85e9 100644
--- a/test/yagni/jvm_test.clj
+++ b/test/yagni/jvm_test.clj
@@ -14,6 +14,10 @@
 (defprotocol SampleInterface
   (foo [this]))
 
+(defn ->non-class-converter
+  []
+  true)
+
 (deftest class-name->var-name
   (is (= (jvm/class-name->var-name yagni.jvm_test.SampleInterface)
          'yagni.jvm-test/SampleInterface)))
@@ -26,6 +30,8 @@
 (deftest is-class-generator?-works
   (is (some? (jvm/is-class-generator? 'yagni.jvm-test/->FooType)))
   (is (some? (jvm/is-class-generator? 'yagni.jvm-test/->FooRecord)))
+  (is (false? (jvm/is-class-generator? 'yagni.jvm-test/->non-class-converter)))
+  (is (some? (jvm/is-class-generator? 'yagni.jvm-test/->non-class-converter)))
   (is (some? (jvm/is-class-generator? 'yagni.jvm-test/map->FooRecord))))
 
 (deftest find-generator-fns-works