From 8fe8390933736348351662bb878b5ca17ed47c94 Mon Sep 17 00:00:00 2001
From: Evgeny Poberezkin <e.poberezkin@me.com>
Date: Tue, 30 Aug 2016 20:43:44 +0100
Subject: [PATCH] feat: exception with useful message if $ref cannot be
 resolved

---
 keywords/add_keyword.js |  9 ++++---
 spec/errors.spec.js     | 57 +++++++++++++++++++++++++++++++++++++++++
 spec/v5.spec.js         | 33 ------------------------
 3 files changed, 63 insertions(+), 36 deletions(-)
 create mode 100644 spec/errors.spec.js
 delete mode 100644 spec/v5.spec.js

diff --git a/keywords/add_keyword.js b/keywords/add_keyword.js
index eb125d4..1094763 100644
--- a/keywords/add_keyword.js
+++ b/keywords/add_keyword.js
@@ -21,9 +21,12 @@ module.exports = function (ajv, keyword, jsonPatch, patchSchema) {
       return source;
 
       function getSchema($ref) {
-        if (it.baseId && it.baseId != '#')
-          $ref = url.resolve(it.baseId, $ref);
-        return ajv.getSchema($ref).schema;
+        var id = it.baseId && it.baseId != '#'
+                  ? url.resolve(it.baseId, $ref)
+                  : $ref;
+        var validate = ajv.getSchema(id);
+        if (validate) return validate.schema;
+        throw new Error('can\'t resolve reference ' + $ref + ' from id ' + it.baseId);
       }
     },
     metaSchema: {
diff --git a/spec/errors.spec.js b/spec/errors.spec.js
new file mode 100644
index 0000000..f0050c6
--- /dev/null
+++ b/spec/errors.spec.js
@@ -0,0 +1,57 @@
+'use strict';
+
+var Ajv = require('ajv');
+var addKeywords = require('..');
+var addMerge = require('../keywords/merge');
+var addPatch = require('../keywords/patch');
+var assert = require('assert');
+
+describe('errors', function() {
+  var ajv;
+
+  describe('no v5 option', function() {
+    beforeEach(function() {
+      ajv = new Ajv;
+    });
+
+    it('adding $merge and $patch should throw without v5 option', function() {
+      assert.throws(function() {
+        addKeywords(ajv);
+      });
+    });
+
+    it('adding $merge only should throw without v5 option', function() {
+      assert.throws(function() {
+        addMerge(ajv);
+      });
+    });
+
+    it('adding $patch only should throw without v5 option', function() {
+      assert.throws(function() {
+        addPatch(ajv);
+      });
+    });
+  });
+
+  describe('missing $ref', function() {
+    beforeEach(function() {
+      ajv = new Ajv({ v5: true });
+      addKeywords(ajv);
+    });
+
+    it('should throw exception if cannot resolve $ref', function() {
+      var schema = {
+        "$merge": {
+          "source": { "$ref": "obj.json#" },
+          "with": {
+            "properties": { "q": { "type": "number" } }
+          }
+        }
+      };
+
+      assert.throws(function() {
+        ajv.compile(schema);
+      });
+    });
+  });
+});
diff --git a/spec/v5.spec.js b/spec/v5.spec.js
deleted file mode 100644
index ef0bf12..0000000
--- a/spec/v5.spec.js
+++ /dev/null
@@ -1,33 +0,0 @@
-'use strict';
-
-var Ajv = require('ajv');
-var addKeywords = require('..');
-var addMerge = require('../keywords/merge');
-var addPatch = require('../keywords/patch');
-var assert = require('assert');
-
-describe('v5 option is required', function() {
-  var ajv;
-
-  beforeEach(function() {
-    ajv = new Ajv;
-  });
-
-  it('adding $merge and $patch should throw without v5 option', function() {
-    assert.throws(function() {
-      addKeywords(ajv);
-    });
-  });
-
-  it('adding $merge only should throw without v5 option', function() {
-    assert.throws(function() {
-      addMerge(ajv);
-    });
-  });
-
-  it('adding $patch only should throw without v5 option', function() {
-    assert.throws(function() {
-      addPatch(ajv);
-    });
-  });
-});