feat(for loop): Support range literals (#192)

Tests/StencilTests/ForNodeSpec.swift

@@ -227,7 +227,7 @@ func testForNode() {
           .block(value: "for i"),
       ]
       let parser = TokenParser(tokens: tokens, environment: Environment())
-      let error = TemplateSyntaxError("'for' statements should use the following 'for x in y where condition' `for i`.")
+      let error = TemplateSyntaxError("'for' statements should use the syntax: `for <x> in <y> [where <condition>]")
       try expect(try parser.parse()).toThrow(error)
     }
 
@@ -306,6 +306,11 @@ func testForNode() {
       try expect(result) == "childString=child\nbaseString=base\nbaseInt=1\n"
     }
 
+    $0.it("can iterate in range of variables") {
+      let template: Template = "{% for i in 1...j %}{{ i }}{% endfor %}"
+      try expect(try template.render(Context(dictionary: ["j": 3]))) == "123"
+    }
+
   }
 
 }

Tests/StencilTests/IfNodeSpec.swift

@@ -270,5 +270,22 @@ func testIfNode() {
       let result = try renderNodes(nodes, Context(dictionary: ["instance": SomeType()]))
       try expect(result) == ""
     }
+
+    $0.it("supports closed range variables") {
+      let tokens: [Token] = [
+        .block(value: "if value in 1...3"),
+        .text(value: "true"),
+        .block(value: "else"),
+        .text(value: "false"),
+        .block(value: "endif")
+      ]
+
+      let parser = TokenParser(tokens: tokens, environment: Environment())
+      let nodes = try parser.parse()
+
+      try expect(renderNodes(nodes, Context(dictionary: ["value": 3]))) == "true"
+      try expect(renderNodes(nodes, Context(dictionary: ["value": 4]))) == "false"
+    }
+
   }
 }

Tests/StencilTests/VariableSpec.swift

@@ -189,4 +189,52 @@ func testVariable() {
       try expect(result) == 2
     }
   }
+
+  describe("RangeVariable") {
+
+    let context: Context = {
+      let ext = Extension()
+      ext.registerFilter("incr", filter: { (arg: Any?) in toNumber(value: arg!)! + 1 })
+      let environment = Environment(extensions: [ext])
+      return Context(dictionary: [:], environment: environment)
+    }()
+
+    func makeVariable(_ token: String) throws -> RangeVariable? {
+      return try RangeVariable(token, parser: TokenParser(tokens: [], environment: context.environment))
+    }
+
+    $0.it("can resolve closed range as array") {
+      let result = try makeVariable("1...3")?.resolve(context) as? [Int]
+      try expect(result) == [1, 2, 3]
+    }
+
+    $0.it("can resolve decreasing closed range as reversed array") {
+      let result = try makeVariable("3...1")?.resolve(context) as? [Int]
+      try expect(result) == [3, 2, 1]
+    }
+
+    $0.it("can use filter on range variables") {
+      let result = try makeVariable("1|incr...3|incr")?.resolve(context) as? [Int]
+      try expect(result) == [2, 3, 4]
+    }
+
+    $0.it("throws when left value is not int") {
+      let template: Template = "{% for i in k...j %}{{ i }}{% endfor %}"
+      try expect(try template.render(Context(dictionary: ["j": 3, "k": "1"]))).toThrow()
+    }
+
+    $0.it("throws when right value is not int") {
+      let variable = try makeVariable("k...j")
+      try expect(try variable?.resolve(Context(dictionary: ["j": "3", "k": 1]))).toThrow()
+    }
+
+    $0.it("throws is left range value is missing") {
+      try  expect(makeVariable("...1")).toThrow()
+    }
+
+    $0.it("throws is right range value is missing") {
+      try  expect(makeVariable("1...")).toThrow()
+    }
+
+  }
 }