From 482d595d011cc06262a3b6d57827fa973af9ca74 Mon Sep 17 00:00:00 2001
From: Jan Berkel <jan@berkel.fr>
Date: Fri, 1 Sep 2017 11:59:52 +0200
Subject: [PATCH] fix(lexer): Handle incomplete tokens

Fixes #135
---
 CHANGELOG.md                       |  2 ++
 Sources/Lexer.swift                |  3 ++-
 Tests/StencilTests/LexerSpec.swift | 10 ++++++++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e7aac18..5574cce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@
 
 - Fixes a potential crash when using the `{% for %}` template tag with the
   incorrect amount of arguments.
+- Fixes a potential crash when using incomplete tokens in a template for
+  example, `{%%}` or `{{}}`.
 
 
 ## 0.9.0
diff --git a/Sources/Lexer.swift b/Sources/Lexer.swift
index 8e3fa33..b0ad8f9 100644
--- a/Sources/Lexer.swift
+++ b/Sources/Lexer.swift
@@ -5,8 +5,9 @@ struct Lexer {
     self.templateString = templateString
   }
 
-  func createToken(string:String) -> Token {
+  func createToken(string: String) -> Token {
     func strip() -> String {
+      guard string.characters.count > 4 else { return "" }
       let start = string.index(string.startIndex, offsetBy: 2)
       let end = string.index(string.endIndex, offsetBy: -2)
       return string[start..<end].trim(character: " ")
diff --git a/Tests/StencilTests/LexerSpec.swift b/Tests/StencilTests/LexerSpec.swift
index 66667ba..ac9eb50 100644
--- a/Tests/StencilTests/LexerSpec.swift
+++ b/Tests/StencilTests/LexerSpec.swift
@@ -54,5 +54,15 @@ func testLexer() {
       try expect(tokens[0]) == Token.variable(value: "thing")
       try expect(tokens[1]) == Token.variable(value: "name")
     }
+
+    $0.it("can tokenize an unclosed block") {
+      let lexer = Lexer(templateString: "{%}")
+      let _ = lexer.tokenize()
+    }
+
+    $0.it("can tokenize an empty variable") {
+      let lexer = Lexer(templateString: "{{}}")
+      let _ = lexer.tokenize()
+    }
   }
 }