Update property nesting

Deeper nested properties guaranteed to be processed after shallower
nested properties.

Also added strict mode checks for duplicate nested properties.

docs/.vitepress/config.ts

@@ -43,7 +43,7 @@ export default defineConfig({
                         { text: "Source", link: "/tut/crash-course/4-source" },
                         { text: "Derived Source", link: "/tut/crash-course/5-derived-source" },
                         { text: "Table Source", link: "/tut/crash-course/6-table-source" },
-                        { text: "Property Groups", link: "/tut/crash-course/7-property-groups" },
+                        { text: "Nested Properties", link: "/tut/crash-course/7-nested-properties" },
                         { text: "Actions", link: "/tut/crash-course/8-actions" },
                     ]
                 },

docs/api/strict-mode.md

@@ -15,7 +15,8 @@ Currently, strict mode will:
 2. Run watchers twice when a source updates.
 3. Throw an error if yields occur where they are not allowed.
 4. Checks for `indexes()` and `values()` returning primitive values.
-5. Better error reporting and stack traces.
+5. Checks for duplicate nested properties at same depth.
+6. Better error reporting and stack traces.
 
 By rerunning sources and watchers, any side-effects are made more apparent.
 This also helps ensure that cleanups are being handled correctly.

docs/tut/crash-course/7-nested-properties.md

@@ -1,4 +1,4 @@
-# Property Groups
+# Nested Properties
 
 Often when creating components from existing components, you can find yourself
 repetitively passing through properties such as size or position.
@@ -99,3 +99,22 @@ List {
     }
 }
 ```
+
+Deeper nested properties are guaranteed to be set after shallower nested
+properties, this can be used to create overridable default properties.
+
+```lua
+local function CenteredList(props: Children & Layout)
+    return List {
+        Layout = {
+            props.Layout,
+
+            -- can be overriden by `props.Layout`
+            AnchorPoint = Vector2.new(0.5, 0),
+            Position = UDim2.fromScale(0.5, 0)
+        },
+
+        Children = props.Children
+    }
+end
+```

src/apply.luau

@@ -5,11 +5,12 @@ if not game then
     typeof = require "test/mock".typeof
 end
 
-local graph = require(script.Parent.graph)
+local flags = require(script.Parent.flags)
-type Node<T> = graph.Node<T>
+local throw = require(script.Parent.throw)
-
 local bind = require(script.Parent.bind)
 local _, is_action = require(script.Parent.action)()
+local graph = require(script.Parent.graph)
+type Node<T> = graph.Node<T>
 
 local event_buffer: { [string]: () -> () } = {}
 local action_buffers = {} :: { { () -> () } }
@@ -21,15 +22,42 @@ setmetatable(action_buffers :: any, {
     end
 })
 
-local function recurse(instance: Instance, properties: { [unknown]: unknown })
+local nested_debug_cache: { [number]: { [string]: true } } = {}
+
+setmetatable(nested_debug_cache :: any, {
+    __index = function(_, i: number)
+        nested_debug_cache[i] = {}
+        return nested_debug_cache[i]
+    end
+})
+
+local nested_stack = {} :: { {} | number }
+
+local function process(instance: Instance, properties: { [unknown]: unknown })
+    local strict = flags.strict
+
+    table.clear(nested_stack)
+    if strict then table.clear(nested_debug_cache) end
+
+    local depth = 1
+
+    repeat
         for property, value in properties do
             if type(value) == "table" then
                 if is_action(value) then
                     table.insert(action_buffers[(value :: any).priority], (value :: any).callback :: () -> ())
                 else
-                recurse(instance, value :: {})
+                    table.insert(nested_stack, depth + 1)
+                    table.insert(nested_stack, value :: {})
                 end
             elseif type(property) == "string" then
+                if strict then
+                    if nested_debug_cache[depth][property] then
+                        throw(`duplicate property {property} at depth {depth}`)
+                    end
+                    nested_debug_cache[depth][property] = true
+                end
+
                 if type(value) == "function" then
                     if typeof((instance :: any)[property]) == "RBXScriptSignal" then
                         event_buffer[property] = value  :: () -> ()
@@ -47,6 +75,11 @@ local function recurse(instance: Instance, properties: { [unknown]: unknown })
                 end
             end
         end
+
+    properties = table.remove(nested_stack) :: {}
+    depth = table.remove(nested_stack) :: number
+
+    until not properties
 end
 
 local function apply<T>(instance: T & Instance, properties: { [unknown]: unknown }): T
@@ -58,7 +91,7 @@ local function apply<T>(instance: T & Instance, properties: { [unknown]: unknown
         table.clear(buffer)
     end
 
-    recurse(instance, properties)
+    process(instance, properties)
 
     for event, fn in next, event_buffer do
         (instance :: any)[event]:Connect(fn)   

test/tests.luau

@@ -596,6 +596,20 @@ TEST("create()", function()
         CHECK(text.Text == "test")
     end
 
+    do CASE "nested precedence"
+        local text = create "TextLabel" {
+            Group = {
+                Text = "1",
+
+                {
+                    Text = "2"
+                }
+            }
+        }
+
+        CHECK(text.Text == "2")
+    end
+
     do CASE "independent"
         local frame = create "Frame"
         CHECK(frame {} ~= frame {})
@@ -1153,6 +1167,7 @@ end)
 TEST("strict", function()
     vide.strict = true
 
+    local create = vide.create
     local source = vide.source
     local derive = vide.derive
     local watch = vide.watch
@@ -1231,6 +1246,34 @@ TEST("strict", function()
 
         CHECK(not ok)
     end
+
+    do CASE "duplicate properties"
+        local ok = pcall(function()
+            create "TextLabel" {
+                {
+                    Name = "foo"
+                },
+                {
+                    Name = "bar"
+                }
+            }
+        end)
+
+        CHECK(not ok)
+
+        ok = pcall(function()
+            create "TextLabel" {
+                {
+                    Name = "foo",
+                    {
+                        Name = "bar"
+                    }
+                }
+            }
+        end)
+
+        CHECK(ok)
+    end
 end)
 
 local ok = FINISH()