Feature Proposal: Support arrays of objects to be merged in the "with" property

keywords/merge.js

@@ -3,6 +3,31 @@
 var addKeyword = require('./add_keyword');
 var jsonMergePatch = require('json-merge-patch');
 
-module.exports = function(ajv) {
-  addKeyword(ajv, '$merge', jsonMergePatch.apply, { "type": "object" });
+function merge(source, merges) {
+  if (!Array.isArray(merges))
+    return jsonMergePatch.apply(source, merges);
+
+  var merged = source;
+
+  merges.forEach(function (m) {
+    merged = jsonMergePatch.apply(source, m);
+  });
+
+  return merged;
+}
+
+module.exports = function (ajv) {
+  addKeyword(ajv, '$merge', merge, {
+    "oneOf": [
+      {
+        "type": "object"
+      },
+      {
+        "type": "array",
+        "items": {
+          "type": "object"
+        }
+      }
+    ]
+  });
 };

spec/merge.spec.js

@@ -157,4 +157,31 @@ describe('keyword $merge', function() {
       test(validate, '$merge');
     }
   });
+
+  it('should extend schema defined in $merge', function() {
+    ajvInstances.forEach(testMerge);
+
+    function testMerge(ajv) {
+      var schema = {
+        "$merge": {
+          "source": {
+            "type": "object",
+            "properties": { "p": { "type": "string" } },
+            "additionalProperties": false
+          },
+          "with": [
+            {
+              "required": [ "q" ]
+            },
+            {
+              "properties": { "q": { "type": "number" } }
+            }
+          ]
+        }
+      };
+
+      var validate = ajv.compile(schema);
+      test(validate, '$merge');
+    }
+  });
 });