Fix #756: Add keys transform and intersection operator to filter expressions.

docs/user/filter_expressions.rst

@@ -270,6 +270,27 @@ filter expressions.
       object varies depending on the recipe, and use of this property is only
       recommended if you are familiar with the argument schema.
 
+Operators
+---------
+This section describes the special operators available to filter expressions on
+top of the standard operators in JEXL. They're documented as functions, and the
+parameters correspond to the operands.
+
+.. js:function:: intersect(list1, list2)
+
+   Returns an array of all values in ``list1`` that are also present in
+   ``list2``. Values are compared using strict equality.
+
+   :param list1:
+      The array to the left of the operator.
+   :param list2:
+      The array to the right of the operator
+
+   .. code-block:: javascript
+
+      // Evaluates to [2, 3]
+      [1, 2, 3, 4] intersect [5, 6, 2, 7, 3]
+
 Transforms
 ----------
 This section describes the transforms available to filter expressions, and what
@@ -359,6 +380,21 @@ function is the value being transformed.
 
    .. _ISO 8601: https://www.w3.org/TR/NOTE-datetime
 
+.. js:function:: keys(obj)
+
+   Return an array of the given object's own keys (specifically, its enumerable
+   properties). Equivalent to `Object.keys`_.
+
+   :param obj:
+      Object to get the keys for.
+
+   .. code-block:: javascript
+
+      // Evaluates to ['foo', 'bar']
+      {foo: 1, bar:2}|keys
+
+   .. _Object.keys: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
+
 Preference Filters
 ^^^^^^^^^^^^^^^^^^
 .. js:function:: preferenceValue(prefKey, defaultValue)

recipe-client-addon/lib/FilterExpressions.jsm

@@ -31,7 +31,9 @@ XPCOMUtils.defineLazyGetter(this, "jexl", () => {
     preferenceValue: PreferenceFilters.preferenceValue,
     preferenceIsUserSet: PreferenceFilters.preferenceIsUserSet,
     preferenceExists: PreferenceFilters.preferenceExists,
+    keys,
   });
+  jexl.addBinaryOp("intersect", 40, operatorIntersect);
   return jexl;
 });
 
@@ -41,3 +43,23 @@ this.FilterExpressions = {
     return jexl.eval(onelineExpr, context);
   },
 };
+
+/**
+ * Return an array of the given object's own keys (specifically, its enumerable
+ * properties).
+ * @param {Object} obj
+ * @return {Array[String]}
+ */
+function keys(obj) {
+  return Object.keys(obj);
+}
+
+/**
+ * Find all the values that are present in both lists.
+ * @param {Array} listA
+ * @param {Array} listB
+ * @return {Array}
+ */
+function operatorIntersect(listA, listB) {
+  return listA.filter(item => listB.includes(item));
+}

recipe-client-addon/test/browser/browser_FilterExpressions.js

@@ -91,3 +91,53 @@ add_task(async function() {
   val = await FilterExpressions.eval('"normandy.test.value"|preferenceExists == true');
   ok(val, "preferenceExists expression fails existence check appropriately");
 });
+
+// keys tests
+add_task(async function testKeys() {
+  let val;
+
+  // Test an object defined in JEXL
+  val = await FilterExpressions.eval("{foo: 1, bar: 2}|keys");
+  Assert.deepEqual(
+    new Set(val),
+    new Set(["foo", "bar"]),
+    "keys returns the keys from an object in JEXL",
+  );
+
+  // Test an object in the context
+  const context = {ctxObject: {baz: "string", biff: NaN}};
+  val = await FilterExpressions.eval("ctxObject|keys", context);
+
+  Assert.deepEqual(
+    new Set(val),
+    new Set(["baz", "biff"]),
+    "keys returns the keys from an object in the context",
+  );
+});
+
+// intersect tests
+add_task(async function testIntersect() {
+  let val;
+
+  val = await FilterExpressions.eval("[1, 2, 3] intersect [4, 2, 6, 7, 3]");
+  Assert.deepEqual(
+    new Set(val),
+    new Set([2, 3]),
+    "intersect finds the common elements between two lists in JEXL",
+  );
+
+  const context = {left: [5, 7], right: [4, 5, 3]};
+  val = await FilterExpressions.eval("left intersect right", context);
+  Assert.deepEqual(
+    new Set(val),
+    new Set([5]),
+    "intersect finds the common elements between two lists in the context",
+  );
+
+  val = await FilterExpressions.eval("['string', 2] intersect [4, 'string', 'other', 3]");
+  Assert.deepEqual(
+    new Set(val),
+    new Set(["string"]),
+    "intersect can compare strings",
+  );
+});