From a1cebd8d0d36e8221c861364b98476d6a06df6ca Mon Sep 17 00:00:00 2001
From: Bruce Hill <bitbucket@bruce-hill.com>
Date: Mon, 5 Feb 2018 17:33:26 -0800
Subject: [PATCH] Fix for debug.upvalue(). This should make it faster (stop
 scanning when it hits the desired upvalue) and more correct (allow setting an
 upvalue to a falsey or nil value: debug.upvalue(fn, 'foo', nil), which is
 different from debug.upvalue(fn, 'foo')).

---
 moon/init.lua  | 19 +++++++++----------
 moon/init.moon | 19 ++++++++-----------
 2 files changed, 17 insertions(+), 21 deletions(-)

diff --git a/moon/init.lua b/moon/init.lua
index d4c2490..b828a02 100644
--- a/moon/init.lua
+++ b/moon/init.lua
@@ -25,25 +25,24 @@ type = function(value)
   return base_type
 end
 debug = setmetatable({
-  upvalue = function(fn, k, v)
-    local upvalues = { }
+  upvalue = function(fn, k, ...)
+    local value = nil
     local i = 1
     while true do
-      local name = lua.debug.getupvalue(fn, i)
+      local name
+      name, value = lua.debug.getupvalue(fn, i)
       if name == nil then
+        error("Failed to find upvalue: " .. tostring(k))
+      end
+      if name == k then
         break
       end
-      upvalues[name] = i
       i = i + 1
     end
-    if not upvalues[k] then
-      error("Failed to find upvalue: " .. tostring(k))
-    end
-    if not v then
-      local _, value = lua.debug.getupvalue(fn, upvalues[k])
+    if select("#", ...) == 0 then
       return value
     else
-      return lua.debug.setupvalue(fn, upvalues[k], v)
+      return lua.debug.setupvalue(fn, i, ...)
     end
   end
 }, {
diff --git a/moon/init.moon b/moon/init.moon
index 658d886..46d5ff1 100644
--- a/moon/init.moon
+++ b/moon/init.moon
@@ -18,23 +18,20 @@ type = (value) -> -- class aware type
   base_type
 
 debug = setmetatable {
-  upvalue: (fn, k, v) ->
-    upvalues = {}
+  upvalue: (fn, k, ...) ->
+    value = nil
     i = 1
     while true
-      name = lua.debug.getupvalue(fn, i)
-      break if name == nil
-      upvalues[name] = i
+      name, value = lua.debug.getupvalue(fn, i)
+      if name == nil
+        error "Failed to find upvalue: " .. tostring k
+      break if name == k
       i += 1
 
-    if not upvalues[k]
-      error "Failed to find upvalue: " .. tostring k
-
-    if not v
-      _, value = lua.debug.getupvalue fn, upvalues[k]
+    if select("#", ...) == 0
       value
     else
-      lua.debug.setupvalue fn, upvalues[k], v
+      lua.debug.setupvalue fn, i, ...
 }, __index: lua.debug
 
 -- run a function with scope injected before its function environment