From d7af9698f9322c29063ed70f8723531955910dc6 Mon Sep 17 00:00:00 2001
From: Joseph Humfrey <joseph.humfrey@inklestudios.com>
Date: Wed, 21 Nov 2018 12:14:38 +0000
Subject: [PATCH] Fix for ResetCallstack() not resetting base callstack
 element.

---
 ink-engine-runtime/CallStack.cs  | 23 +++++++++++++++++------
 ink-engine-runtime/StoryState.cs |  8 ++------
 tests/Tests.cs                   | 31 +++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 12 deletions(-)

diff --git a/ink-engine-runtime/CallStack.cs b/ink-engine-runtime/CallStack.cs
index 15d44300..4e396e07 100644
--- a/ink-engine-runtime/CallStack.cs
+++ b/ink-engine-runtime/CallStack.cs
@@ -176,22 +176,31 @@ public bool canPop {
             }
         }
 
-        public CallStack (Container rootContentContainer)
+        public CallStack (Story storyContext)
         {
-            _threads = new List<Thread> ();
-            _threads.Add (new Thread ());
-
-            _threads [0].callstack.Add (new Element (PushPopType.Tunnel, Pointer.StartOf(rootContentContainer)));
+            _startOfRoot = Pointer.StartOf(storyContext.rootContentContainer);
+            Reset();
         }
 
+
         public CallStack(CallStack toCopy)
         {
             _threads = new List<Thread> ();
             foreach (var otherThread in toCopy._threads) {
                 _threads.Add (otherThread.Copy ());
             }
+            _startOfRoot = toCopy._startOfRoot;
         }
-            
+
+        public void Reset() 
+        {
+            _threads = new List<Thread>();
+            _threads.Add(new Thread());
+
+            _threads[0].callstack.Add(new Element(PushPopType.Tunnel, _startOfRoot));
+        }
+
+
         // Unfortunately it's not possible to implement jsonToken since
         // the setter needs to take a Story as a context in order to
         // look up objects from paths for currentContainer within elements.
@@ -208,6 +217,7 @@ public void SetJsonToken(Dictionary<string, object> jObject, Story storyContext)
             }
 
             _threadCounter = (int)jObject ["threadCounter"];
+            _startOfRoot = Pointer.StartOf(storyContext.rootContentContainer);
         }
             
         // See above for why we can't implement jsonToken
@@ -399,6 +409,7 @@ internal string callStackTrace {
 
         List<Thread> _threads;
         int _threadCounter;
+        Pointer _startOfRoot;
     }
 }
 
diff --git a/ink-engine-runtime/StoryState.cs b/ink-engine-runtime/StoryState.cs
index a3e8ea72..1ed41925 100755
--- a/ink-engine-runtime/StoryState.cs
+++ b/ink-engine-runtime/StoryState.cs
@@ -247,7 +247,7 @@ internal StoryState (Story story)
 
             evaluationStack = new List<Runtime.Object> ();
 
-            callStack = new CallStack (story.rootContentContainer);
+            callStack = new CallStack (story);
             variablesState = new VariablesState (callStack, story.listDefinitions);
 
             visitCounts = new Dictionary<string, int> ();
@@ -809,11 +809,7 @@ internal Runtime.Object PeekEvaluationStack()
         /// </summary>
         public void ForceEnd()
         {
-            while (callStack.canPopThread)
-                callStack.PopThread ();
-
-            while (callStack.canPop)
-                PopCallstack ();
+            callStack.Reset();
 
 			_currentChoices.Clear();
 
diff --git a/tests/Tests.cs b/tests/Tests.cs
index 7b5fd80f..d4a1dd62 100644
--- a/tests/Tests.cs
+++ b/tests/Tests.cs
@@ -3658,6 +3658,37 @@ public void TestFallbackChoiceOnThread()
             Assert.AreEqual("Should be 1 not 0: 1.\n", story.Continue());
         }
 
+        // Test for bug where after a call to ChoosePathString,
+        // the callstack is not fully/cleanly reset, e.g. leaving
+        // "inExpressionEvaluation" variable left to true, as set during
+        // the call to {RunAThing()}.
+        // This was when we unwound the callstack, but we didn't reset
+        // the base element.
+        [Test()]
+        public void TestCleanCallstackResetOnPathChoice()
+        {
+            var storyStr =
+        @"
+{RunAThing()}
+
+== function RunAThing ==
+The first line.
+The second line.
+
+== SomewhereElse ==
+{""somewhere else""}
+->END
+";
+
+            var story = CompileString(storyStr);
+
+            Assert.AreEqual("The first line.\n", story.Continue());
+
+            story.ChoosePathString("SomewhereElse");
+
+            Assert.AreEqual("somewhere else\n", story.ContinueMaximally());
+        }
+
         // Helper compile function
         protected Story CompileString(string str, bool countAllVisits = false, bool testingErrors = false)
         {