Lua-side implementation of getter/setter callbacks.

src/main/java/li/cil/oc/api/machine/Callback.java

@@ -95,9 +95,18 @@ public @interface Callback {
      * Whether this callback should work like a getter.
      * <p/>
      * Callbacks that are getters do not appear as methods on a component's
-     * proxy. Instead they are accessed via the proxy's <tt>__index</tt>
-     * metamethod, i.e. it is accessed as a field, with it's only parameter
-     * being the accessed key.
+     * proxy. Instead they are accessed as fields, for example in Lua via the
+     * proxy's <tt>__index</tt> metamethod, with it's only parameter being the
+     * accessed key.
+     * <p/>
+     * Note: if you wish to have a field that is read/write, that is you need
+     * both a getter and a setter, you have to implement them in the same
+     * method. This a limitation due to callback names being unique. You can
+     * differentiate between contexts by checking the number of arguments.
+     * <p/>
+     * <em>Important</em>: this only works in environments (for components),
+     * it does <em>not</em> work for userdata (<tt>Value</tt> objects). For
+     * userdata, use the <tt>apply</tt> method instead.
      */
     boolean getter() default false;
 
@@ -105,9 +114,18 @@ public @interface Callback {
      * Whether this callback should work like a setter.
      * <p/>
      * Callbacks that are setters do not appear as methods on a component's
-     * proxy. Instead they are accessed via the proxy's <tt>__newindex</tt>
-     * metamethod, i.e. it is accessed as a field, with it's only parameters
-     * being the accessed key and the assigned value.
+     * proxy. Instead they are accessed as fields, for example in Lua via the
+     * proxy's <tt>__newindex</tt> metamethod, with it's only tow parameters
+     * being the accessed key and the new value.
+     * <p/>
+     * Note: if you wish to have a field that is read/write, that is you need
+     * both a getter and a setter, you have to implement them in the same
+     * method. This a limitation due to callback names being unique. You can
+     * differentiate between contexts by checking the number of arguments.
+     * <p/>
+     * <em>Important</em>: this only works in environments (for components),
+     * it does <em>not</em> work for userdata (<tt>Value</tt> objects). For
+     * userdata, use the <tt>unapply</tt> method instead.
      */
     boolean setter() default false;
 }

src/main/resources/assets/opencomputers/lua/kernel.lua

@@ -468,12 +468,65 @@ end
 
 local libcomponent
 
+-- Caching proxy objects for lower memory use.
 local proxyCache = setmetatable({}, {__mode="v"})
-local proxyDirectCache = setmetatable({}, {__mode="k"})
+
+-- Short-term caching of callback directness for improved performance.
+local directCache = setmetatable({}, {__mode="k"})
+local function isDirect(address, method)
+  local cacheKey = address..":"..method
+  local cachedValue = directCache[cacheKey]
+  if cachedValue ~= nil then
+    return cachedValue
+  end
+  local methods, reason = spcall(component.methods, address)
+  if methods then
+    for name, info in pairs(methods) do
+      if name == method then
+        directCache[cacheKey] = info.direct
+        return info.direct
+      end
+    end
+  end
+  error("no such method", 1)
+end
+
+local componentProxy = {
+  __index = function(self, key)
+    if self.fields[key] and self.fields[key].getter then
+      return libcomponent.invoke(self.address, key)
+    else
+      rawget(self, key)
+    end
+  end,
+  __newindex = function(self, key, value)
+    if self.fields[key] and self.fields[key].setter then
+      return libcomponent.invoke(self.address, key, value)
+    elseif self.fields[key] and self.fields[key].getter then
+      error("field is read-only")
+    else
+      rawset(self, key, value)
+    end
+  end,
+  __pairs = function(self)
+    local keyProxy, keyField, value
+    return function()
+      if not keyField then
+        repeat
+          keyProxy, value = next(self, keyProxy)
+        until not keyProxy or keyProxy ~= "fields"
+      end
+      if not keyProxy then
+        keyField, value = next(self.fields, keyField)
+      end
+      return keyProxy or keyField, value
+    end
+  end
+}
 
 local componentCallback = {
   __call = function(self, ...)
-    return invoke(component, not not proxyDirectCache[self], self.address, self.name, ...)
+    return libcomponent.invoke(self.address, self.name, ...)
   end,
   __tostring = function(self)
     return libcomponent.doc(self.address, self.name) or "function"
@@ -493,16 +546,7 @@ libcomponent = {
   invoke = function(address, method, ...)
     checkArg(1, address, "string")
     checkArg(2, method, "string")
-    local methods, reason = spcall(component.methods, address)
-    if not methods then
-      return nil, reason
-    end
-    for name, direct in pairs(methods) do
-      if name == method then
-        return invoke(component, direct, address, method, ...)
-      end
-    end
-    error("no such method", 1)
+    return invoke(component, isDirect(address, method), address, method, ...)
   end,
   list = function(filter, exact)
     checkArg(1, filter, "string", "nil")
@@ -516,7 +560,31 @@ libcomponent = {
     end})
   end,
   methods = function(address)
-    return spcall(component.methods, address)
+    local result, reason = spcall(component.methods, address)
+    -- Transform to pre 1.4 format to avoid breaking scripts.
+    if type(result) == "table" then
+      for k, v in pairs(result) do
+        if not v.getter and not v.setter then
+          result[k] = v.direct
+        else
+          result[k] = nil
+        end
+      end
+      return result
+    end
+    return result, reason
+  end,
+  fields = function(address)
+    local result, reason = spcall(component.methods, address)
+    if type(result) == "table" then
+      for k, v in pairs(result) do
+        if not v.getter and not v.setter then
+          result[k] = nil
+        end
+      end
+      return result
+    end
+    return result, reason
   end,
   proxy = function(address)
     local type, reason = spcall(component.type, address)
@@ -530,15 +598,19 @@ libcomponent = {
     if proxyCache[address] then
       return proxyCache[address]
     end
-    local proxy = {address = address, type = type, slot = slot}
+    local proxy = {address = address, type = type, slot = slot, fields = {}}
     local methods, reason = spcall(component.methods, address)
     if not methods then
       return nil, reason
     end
-    for method, direct in pairs(methods) do
-      proxy[method] = setmetatable({address=address,name=method}, componentCallback)
-      proxyDirectCache[proxy[method]] = direct
+    for method, info in pairs(methods) do
+      if not info.getter and not info.setter then
+        proxy[method] = setmetatable({address=address,name=method}, componentCallback)
+      else
+        proxy.fields[method] = info
+      end
     end
+    setmetatable(proxy, componentProxy)
     proxyCache[address] = proxy
     return proxy
   end,

src/main/scala/li/cil/oc/server/machine/luac/ComponentAPI.scala

@@ -57,7 +57,13 @@ class ComponentAPI(owner: NativeLuaArchitecture) extends NativeLuaAPI(owner) {
         lua.newTable()
         for ((name, annotation) <- machine.methods(component.host)) {
           lua.pushString(name)
+          lua.newTable()
           lua.pushBoolean(annotation.direct)
+          lua.setField(-2, "direct")
+          lua.pushBoolean(annotation.getter)
+          lua.setField(-2, "getter")
+          lua.pushBoolean(annotation.setter)
+          lua.setField(-2, "setter")
           lua.rawSet(-3)
         }
         1

src/main/scala/li/cil/oc/server/machine/luaj/ComponentAPI.scala

@@ -48,7 +48,13 @@ class ComponentAPI(owner: LuaJLuaArchitecture) extends LuaJAPI(owner) {
       withComponent(args.checkjstring(1), component => {
         val table = LuaValue.tableOf()
         for ((name, annotation) <- machine.methods(component.host)) {
-          table.set(name, LuaValue.valueOf(annotation.direct))
+          table.set(name, LuaValue.tableOf(Array(
+            LuaValue.valueOf("direct"),
+            LuaValue.valueOf(annotation.direct),
+            LuaValue.valueOf("getter"),
+            LuaValue.valueOf(annotation.getter),
+            LuaValue.valueOf("setter"),
+            LuaValue.valueOf(annotation.setter))))
         }
         table
       })