Add more helpful link to error explanation - missing composer config

README.md

@@ -58,3 +58,4 @@ Documentation
 
 * [Unknown namespace - (Unregistered)](docs/exceptions/unregisteredRoot.md)
 * [Unknown namespace - (Registered)](docs/exceptions/unknownSubNamespace.md)
+* [Missing composer.json](docs/exceptions/missingComposerConfig.md)

docs/exceptions/missingComposerConfig.md

@@ -0,0 +1,36 @@
+Missing composer.json
+---------------------
+
+Example PHP:
+```
+<?php
+
+require_once __DIR__ . '/../vendor/autoload.php';
+
+use HaydenPierce\ClassFinder\ClassFinder;
+
+$classes = ClassFinder::getClassesInNamespace('Acme\Foo\Bar');
+```
+
+Results in this exception:
+
+> Could not locate composer.json. You can get around this by setting ClassFinder::$appRoot manually.
+
+ClassFinder requires a composer.json to load autoloading settings. In this situation, ClassFinder wasn't able to 
+find it when recursively searching for it. You will need to tell ClassFinder where the root of your application is - this
+is the directory that contains the composer.json configuration and where classes will be searched out of.
+
+```
+<?php
+
+require_once __DIR__ . '/../vendor/autoload.php';
+
+use HaydenPierce\ClassFinder\ClassFinder;
+
+ClassFinder::$appRoot = realpath(__DIR__ . '../../app/'); // This is suggesting that the app root is really someone else.
+$classes = ClassFinder::getClassesInNamespace('Acme\Foo\Bar');
+```
+
+This is an exotic situation and shouldn't apply to most projects.
+
+

src/ClassFinder.php

@@ -30,7 +30,7 @@ class ClassFinder
 
         if (!file_exists($appRoot . '/composer.json')) {
             throw new ClassFinderException(sprintf("Could not locate composer.json. You can get around this by setting ClassFinder::\$appRoot manually. See '%s' for details.",
-                'https://gitlab.com/hpierce1102/ClassFinder' // TODO: write documentation and update this link.
+                'https://gitlab.com/hpierce1102/ClassFinder/blob/master/docs/exceptions/missingComposerConfig.md'
                 ));
         } else {
             self::$appRoot = $appRoot;