[for block] Handle empty nodes

Closes #35

StencilSpecs/Nodes/ForNodeSpec.swift

@@ -0,0 +1,23 @@
+import Spectre
+import Stencil
+
+
+describe("ForNode") {
+  let context = Context(dictionary: [
+    "items": [1, 2, 3],
+    "emptyItems": [Int](),
+  ])
+
+  $0.it("renders the given nodes for each item") {
+    let nodes: [NodeType] = [VariableNode(variable: "item")]
+    let node = ForNode(variable: "items", loopVariable: "item", nodes: nodes, emptyNodes: [])
+    try expect(try node.render(context)) == "123"
+  }
+
+  $0.it("renders the given empty nodes when no items found item") {
+    let nodes: [NodeType] = [VariableNode(variable: "item")]
+    let emptyNodes: [NodeType] = [TextNode(text: "empty")]
+    let node = ForNode(variable: "emptyItems", loopVariable: "item", nodes: nodes, emptyNodes: emptyNodes)
+    try expect(try node.render(context)) == "empty"
+  }
+}

StencilSpecs/Nodes/NodeSpec.swift

@@ -55,12 +55,4 @@ describe("Node") {
       try expect(try renderNodes(nodes, context)).toThrow(TemplateSyntaxError("Custom Error"))
     }
   }
-
-  $0.describe("ForNode") {
-    $0.it("renders the given nodes for each item") {
-      let nodes: [NodeType] = [VariableNode(variable: "item")]
-      let node = ForNode(variable: "items", loopVariable: "item", nodes: nodes, emptyNodes: [])
-      try expect(try node.render(context)) == "123"
-    }
-  }
 }