From e7a0738bda6fbb41b34bd884de5447bc7a6c8e3e Mon Sep 17 00:00:00 2001
From: Ilya Puchka <ilyapuchka@gmail.com>
Date: Mon, 2 Oct 2017 10:38:50 +0200
Subject: [PATCH] fix(variable): checking values for nil when using mirror
 (#144)

---
 CHANGELOG.md                        |  1 +
 Sources/Variable.swift              |  4 ++++
 Tests/StencilTests/IfNodeSpec.swift | 17 +++++++++++++++++
 3 files changed, 22 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c123c4e..712796b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@
   incorrect amount of arguments.
 - Fixes a potential crash when using incomplete tokens in a template for
   example, `{%%}` or `{{}}`.
+- Fixes evaluating nil properties as true
 
 
 ## 0.9.0
diff --git a/Sources/Variable.swift b/Sources/Variable.swift
index c330d64..239f252 100644
--- a/Sources/Variable.swift
+++ b/Sources/Variable.swift
@@ -105,6 +105,10 @@ public struct Variable : Equatable, Resolvable {
 
         if current == nil {
           return nil
+          // mirror returns non-nil value even for nil-containing properties
+          // so we have to check if its value is actually nil or not
+        } else if let current = current, String(describing: current) == "nil" {
+          return nil
         }
       } else {
         return nil
diff --git a/Tests/StencilTests/IfNodeSpec.swift b/Tests/StencilTests/IfNodeSpec.swift
index f174b6a..c77122f 100644
--- a/Tests/StencilTests/IfNodeSpec.swift
+++ b/Tests/StencilTests/IfNodeSpec.swift
@@ -253,5 +253,22 @@ func testIfNode() {
         let result = try renderNodes(nodes, Context(dictionary: ["value": "test"]))
         try expect(result) == "true"
     }
+    
+    $0.it("evaluates nil properties as false") {
+      let tokens: [Token] = [
+        .block(value: "if instance.value"),
+        .text(value: "true"),
+        .block(value: "endif")
+      ]
+      
+      let parser = TokenParser(tokens: tokens, environment: Environment())
+      let nodes = try parser.parse()
+      
+      struct SomeType {
+        let value: String? = nil
+      }
+      let result = try renderNodes(nodes, Context(dictionary: ["instance": SomeType()]))
+      try expect(result) == ""
+    }
   }
 }