Liveview Code Review

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name: liveview-code-review description: Reviews Phoenix LiveView code for lifecycle patterns, assigns/streams usage, components, and security. Use when reviewing LiveView modules, .heex templates, or LiveComponents.

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LiveView Code Review

Quick Reference

| Issue Type | Reference | |------------|-----------| | mount, handle_params, handle_event, handle_async | references/lifecycle.md | | When to use assigns vs streams, AsyncResult | references/assigns-streams.md | | Function vs LiveComponent, slots, attrs | references/components.md | | Authorization per event, phx-value trust | references/security.md |

Review Checklist

Critical Issues

[ ] No socket copying into async functions (extract values first)

[ ] Every handle_event validates authorization

[ ] No sensitive data in assigns (visible in DOM)

[ ] phx-value data is validated (user-modifiable)

Lifecycle

[ ] Subscriptions wrapped in connected?(socket)

[ ] handle_params used for URL-based state

[ ] handle_async handles :loading and :error states

Data Management

[ ] Streams used for large collections (100+ items)

[ ] temporary_assigns for data not needed after render

[ ] AsyncResult patterns for loading states

Components

[ ] Function components preferred over LiveComponents

[ ] LiveComponents preserve :inner_block in update/2

[ ] Slots use proper attr declarations

[ ] phx-debounce on text inputs

Valid Patterns (Do NOT Flag)

Empty mount returning {:ok, socket} - Valid for simple LiveViews

Using assigns for small lists - Streams only needed for 100+ items

LiveComponent without update/2 - Default update/2 assigns all

phx-click without phx-value - Event may not need data

Inline function in heex - Valid for simple transforms

Context-Sensitive Rules

| Issue | Flag ONLY IF | |-------|--------------| | Missing debounce | Input is text/textarea AND triggers server event | | Use streams | Collection has 100+ items OR is paginated | | Missing auth check | Event modifies data AND no auth in mount |

Critical Anti-Patterns

Socket Copying (MOST IMPORTANT)

# BAD - socket copied into async function
def handle_event("load", _, socket) do
  Task.async(fn ->
    user = socket.assigns.user  # Socket copied!
    fetch_data(user.id)
  end)
  {:noreply, socket}
end
GOOD - extract values first
def handle_event("load", _, socket) do
  user_id = socket.assigns.user.id
  Task.async(fn ->
    fetch_data(user_id)  # Only primitive copied
  end)
  {:noreply, socket}
end

Missing Authorization

# BAD - trusts phx-value without auth
def handle_event("delete", %{"id" => id}, socket) do
  Posts.delete_post!(id)  # Anyone can delete any post!
  {:noreply, socket}
end
GOOD - verify authorization
def handle_event("delete", %{"id" => id}, socket) do
  post = Posts.get_post!(id)
  if post.user_id == socket.assigns.current_user.id do
    Posts.delete_post!(post)
    {:noreply, stream_delete(socket, :posts, post)}
  else
    {:noreply, put_flash(socket, :error, "Unauthorized")}
  end
end

Hard gates (sequence)

Advance only when each pass condition is objectively true (prevents reporting without evidence):

| Gate | Pass condition | |------|----------------| | G1 — Files in evidence | You have an explicit list of paths under review (e.g. *.ex, *.heex, or the paths the user named). Every finding names a file from that list. | | G2 — Verification protocol | You loaded review-verification-protocol and applied its Pre-Report Verification (and issue-type sections where relevant) before treating something as a finding. | | G3 — Line anchors | Each finding uses [FILE:LINE] where that line exists in the current file (confirmed by read/grep output, not inferred). | | G4 — Valid-pattern screen | You checked the finding against Valid Patterns (Do NOT Flag) and Context-Sensitive Rules; if it matches a “do not flag” case or fails a “Flag ONLY IF,” you do not report it. |

Issue format

Use [FILE:LINE] ISSUE_TITLE for each finding.