From 84b0531e396807c96fb957aaa2a8cd670398891f Mon Sep 17 00:00:00 2001
From: Evgeny Poberezkin <e.poberezkin@me.com>
Date: Tue, 8 Nov 2016 00:49:29 +0000
Subject: [PATCH] feat: async loading of meta-schema, #334

---
 lib/compile/async.js | 28 +++++++++++++++++++++++-----
 spec/async.spec.js   | 20 ++++++++++++++------
 2 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/lib/compile/async.js b/lib/compile/async.js
index aebffbc..d80a12b 100644
--- a/lib/compile/async.js
+++ b/lib/compile/async.js
@@ -8,20 +8,25 @@ module.exports = compileAsync;
  * `loadSchema` option should be a function that accepts schema uri and returns promise that resolves with the schema.
  * @this  Ajv
  * @param {Object}   schema schema object
+ * @param {Boolean}  meta optional true to compile meta-schema; this parameter can be skipped
  * @param {Function} callback an optional node-style callback, it is called with 2 parameters: error (or null) and validating function.
  * @return {Promise} promise that resolves with a validating function.
  */
-function compileAsync(schema, callback) {
+function compileAsync(schema, meta, callback) {
   /* eslint no-shadow: 0 */
   /* global Promise */
   /* jshint validthis: true */
-  var schemaObj;
   var self = this;
   if (typeof this._opts.loadSchema != 'function')
     throw new Error('options.loadSchema should be a function');
 
-  var p = Promise.resolve().then(function () {
-    schemaObj = self._addSchema(schema);
+  if (typeof meta == 'function') {
+    callback = meta;
+    meta = undefined;
+  }
+
+  var p = loadMetaSchemaOf(schema).then(function () {
+    var schemaObj = self._addSchema(schema, undefined, meta);
     return schemaObj.validate || _compileAsync(schemaObj);
   });
 
@@ -35,6 +40,14 @@ function compileAsync(schema, callback) {
   return p;
 
 
+  function loadMetaSchemaOf(sch) {
+    var $schema = sch.$schema;
+    return $schema && !self.getSchema($schema)
+            ? compileAsync.call(self, { $ref: $schema }, true)
+            : Promise.resolve();
+  }
+
+
   function _compileAsync(schemaObj) {
     try { return self._compile(schemaObj); }
     catch(e) {
@@ -54,7 +67,12 @@ function compileAsync(schema, callback) {
       }
 
       return schemaPromise.then(function (sch) {
-        if (!added(ref)) self.addSchema(sch, ref);
+        if (!added(ref)) {
+          return loadMetaSchemaOf(sch).then(function () {
+            if (!added(ref)) self.addSchema(sch, ref, undefined, meta);
+          });
+        }
+      }).then(function() {
         return _compileAsync(schemaObj);
       });
 
diff --git a/spec/async.spec.js b/spec/async.spec.js
index 1702dad..5363e32 100644
--- a/spec/async.spec.js
+++ b/spec/async.spec.js
@@ -177,9 +177,16 @@ describe('compileAsync method', function() {
   });
 
 
-  describe.skip('loading metaschemas (#334)', function() {
+  describe('loading metaschemas (#334)', function() {
     it('should load metaschema if not available', function() {
-      var schema = { "$ref": "http://example.com/foobar.json" };
+      return test(SCHEMAS['http://example.com/foobar.json'], 1);
+    });
+
+    it('should load metaschema of referenced schema if not available', function() {
+      return test({ "$ref": "http://example.com/foobar.json" }, 2);
+    });
+
+    function test(schema, expectedLoadCallCount) {
       ajv.addKeyword('myFooBar', {
         type: 'string',
         validate: function (sch, data) {
@@ -188,12 +195,12 @@ describe('compileAsync method', function() {
       });
 
       return ajv.compileAsync(schema).then(function (validate) {
-        should.equal(loadCallCount, 2);
+        should.equal(loadCallCount, expectedLoadCallCount);
         validate .should.be.a('function');
         validate('foo') .should.equal(true);
         validate('bar') .should.equal(false);
       });
-    });
+    }
   });
 
 
@@ -237,13 +244,14 @@ describe('compileAsync method', function() {
       }
     };
 
-    return Promise.all[
+    return Promise.all([
       ajv.compileAsync(schema).then(spec),
       ajv.compileAsync(schema).then(spec),
       ajv.compileAsync(schema).then(spec)
-    ];
+    ]);
 
     function spec(validate) {
+      should.equal(loadCallCount, 2);
       validate .should.be.a('function');
       validate({ a: { b: 2 } }) .should.equal(true);
       validate({ a: { b: 1 } }) .should.equal(false);