Perform change tracking on form access

lib/phoenix_live_view/engine.ex

@@ -286,6 +286,7 @@ defmodule Phoenix.LiveView.Engine do
   handled lazily by the diff algorithm.
   """
 
+  alias Phoenix.HTML.Form
   @behaviour Phoenix.Template.Engine
 
   @impl true
@@ -571,10 +572,10 @@ defmodule Phoenix.LiveView.Engine do
           [assign | tail] ->
             quote do
               unquote(__MODULE__).nested_changed_assign?(
-                unquote(@assigns_var),
-                changed,
+                unquote(tail),
                 unquote(assign),
-                unquote(tail)
+                unquote(@assigns_var),
+                changed
               )
             end
         end
@@ -725,14 +726,14 @@ defmodule Phoenix.LiveView.Engine do
   defp component_changed([path], assigns, changed) do
     case path do
       [key] -> changed_assign(changed, key)
-      [key | tail] -> nested_changed_assign(assigns, changed, key, tail)
+      [key | tail] -> nested_changed_assign(tail, key, assigns, changed)
     end
   end
 
   defp component_changed(entries, assigns, changed) do
     Enum.any?(entries, fn
       [key] -> changed_assign?(changed, key)
-      [key | tail] -> nested_changed_assign?(assigns, changed, key, tail)
+      [key | tail] -> nested_changed_assign?(tail, key, assigns, changed)
     end)
   end
 
@@ -1192,14 +1193,14 @@ defmodule Phoenix.LiveView.Engine do
   end
 
   @doc false
-  def nested_changed_assign?(assigns, changed, head, tail),
-    do: nested_changed_assign(assigns, changed, head, tail) != false
+  def nested_changed_assign?(tail, head, assigns, changed),
+    do: nested_changed_assign(tail, head, assigns, changed) != false
 
-  defp nested_changed_assign(assigns, changed, head, tail) do
+  defp nested_changed_assign(tail, head, assigns, changed) do
     case changed do
       %{^head => changed} ->
         case assigns do
-          %{^head => assigns} -> recur_changed_assign(assigns, changed, tail)
+          %{^head => assigns} -> recur_changed_assign(tail, assigns, changed)
           %{} -> true
         end
 
@@ -1211,30 +1212,34 @@ defmodule Phoenix.LiveView.Engine do
     end
   end
 
-  defp recur_changed_assign(assigns, changed, [{:struct, head} | tail]) do
-    recur_changed_assign(assigns, changed, head, tail)
+  defp recur_changed_assign([{:struct, head} | tail], assigns, changed) do
+    recur_changed_assign(tail, head, assigns, changed)
+  end
+
+  defp recur_changed_assign([{:access, head}], %Form{} = form1, %Form{} = form2) do
+    Form.input_changed?(form1, form2, head)
   end
 
-  defp recur_changed_assign(assigns, changed, [{:access, head} | tail]) do
+  defp recur_changed_assign([{:access, head} | tail], assigns, changed) do
     if match?(%_{}, assigns) or match?(%_{}, changed) do
       true
     else
-      recur_changed_assign(assigns, changed, head, tail)
+      recur_changed_assign(tail, head, assigns, changed)
     end
   end
 
-  defp recur_changed_assign(assigns, changed, head, []) do
+  defp recur_changed_assign([], head, assigns, changed) do
     case {assigns, changed} do
       {%{^head => value}, %{^head => value}} -> false
       {_, %{^head => value}} when is_map(value) -> value
       {_, _} -> true
     end
   end
 
-  defp recur_changed_assign(assigns, changed, head, tail) do
+  defp recur_changed_assign(tail, head, assigns, changed) do
     case {assigns, changed} do
       {%{^head => assigns_value}, %{^head => changed_value}} ->
-        recur_changed_assign(assigns_value, changed_value, tail)
+        recur_changed_assign(tail, assigns_value, changed_value)
 
       {_, _} ->
         true

mix.lock

@@ -15,7 +15,7 @@
   "mime": {:hex, :mime, "2.0.3", "3676436d3d1f7b81b5a2d2bd8405f412c677558c81b1c92be58c00562bb59095", [:mix], [], "hexpm", "27a30bf0db44d25eecba73755acf4068cbfe26a4372f9eb3e4ea3a45956bff6b"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.2.3", "244836e6e3f1200c7f30cb56733fd808744eca61fd182f731eac4af635cc6d0b", [:mix], [], "hexpm", "c8d789e39b9131acf7b99291e93dae60ab48ef14a7ee9d58c6964f59efb570b0"},
   "phoenix": {:hex, :phoenix, "1.6.15", "0a1d96bbc10747fd83525370d691953cdb6f3ccbac61aa01b4acb012474b047d", [:mix], [{:castore, ">= 0.0.0", [hex: :castore, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 2.0", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:phoenix_view, "~> 1.0 or ~> 2.0", [hex: :phoenix_view, repo: "hexpm", optional: false]}, {:plug, "~> 1.10", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 2.2", [hex: :plug_cowboy, repo: "hexpm", optional: true]}, {:plug_crypto, "~> 1.2", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "d70ab9fbf6b394755ea88b644d34d79d8b146e490973151f248cacd122d20672"},
-  "phoenix_html": {:git, "https://github.com/phoenixframework/phoenix_html.git", "da9c164bbd54c4ca3bfac7e5c914e9430f9a2ef6", []},
+  "phoenix_html": {:git, "https://github.com/phoenixframework/phoenix_html.git", "f829bcbf9e87e5d08595c1ea531e1243f0510bf4", []},
   "phoenix_live_reload": {:hex, :phoenix_live_reload, "1.4.1", "2aff698f5e47369decde4357ba91fc9c37c6487a512b41732818f2204a8ef1d3", [:mix], [{:file_system, "~> 0.2.1 or ~> 0.3", [hex: :file_system, repo: "hexpm", optional: false]}, {:phoenix, "~> 1.4", [hex: :phoenix, repo: "hexpm", optional: false]}], "hexpm", "9bffb834e7ddf08467fe54ae58b5785507aaba6255568ae22b4d46e2bb3615ab"},
   "phoenix_pubsub": {:hex, :phoenix_pubsub, "2.1.1", "ba04e489ef03763bf28a17eb2eaddc2c20c6d217e2150a61e3298b0f4c2012b5", [:mix], [], "hexpm", "81367c6d1eea5878ad726be80808eb5a787a23dee699f96e72b1109c57cdd8d9"},
   "phoenix_template": {:hex, :phoenix_template, "1.0.0", "c57bc5044f25f007dc86ab21895688c098a9f846a8dda6bc40e2d0ddc146e38f", [:mix], [{:phoenix_html, "~> 2.14.2 or ~> 3.0", [hex: :phoenix_html, repo: "hexpm", optional: true]}], "hexpm", "1b066f99a26fd22064c12b2600a9a6e56700f591bf7b20b418054ea38b4d4357"},

test/phoenix_live_view/engine_test.exs

@@ -263,6 +263,21 @@ defmodule Phoenix.LiveView.EngineTest do
       assert changed(template, new_changed_bar, old) == ["777"]
     end
 
+    test "renders dynamic with access tracking for forms" do
+      form1 = Phoenix.Component.to_form(%{"foo" => "bar"})
+      form2 = Phoenix.Component.to_form(%{"foo" => "bar", "baz" => "bat"})
+      form3 = Phoenix.Component.to_form(%{"foo" => "baz"})
+
+      template = "<%= Map.fetch!(@form[:foo], :value) %>"
+      assert changed(template, %{form: form1}, nil) == ["bar"]
+
+      template = "<%= Map.fetch!(@form[:foo], :value) %>"
+      assert changed(template, %{form: form1}, %{}) == [nil]
+      assert changed(template, %{form: form1}, %{form: form1}) == [nil]
+      assert changed(template, %{form: form2}, %{form: form1}) == [nil]
+      assert changed(template, %{form: form3}, %{form: form1}) == ["baz"]
+    end
+
     test "renders dynamic with access tracking inside comprehension" do
       template = """
       <%= for x <- [:a, :b, :c] do %>