elixir-phoenix-liveview-debug

name	elixir-phoenix-liveview-debug
description	Debug LiveView events, assigns, reconnects, and render behavior.
metadata	{"short-description":"Debug LiveView lifecycle issues"}

LiveView Debugging

Use for hard LiveView bugs: state drift, duplicate events, slow renders, reconnect inconsistencies, and stream misuse.

Iron Laws

1. Reproduce first with exact event sequence and params.
2. Track assign ownership by callback boundary (mount, handle_params, handle_event, handle_info).
3. Verify streams for large collections before introducing list assigns.
4. Distinguish transport issues from domain-state issues.
5. Fix root cause, not only UI symptom.

Debug Workflow

Step 1: Build Reproduction Timeline

Capture:

• Initial mount conditions
• URL/param transitions
• User events and payloads
• Incoming PubSub/info messages
• Reconnect behavior

Step 2: Verify State Transitions

Map each callback to:

• Inputs it consumes
• Assigns it mutates
• Side effects it triggers

Look for stale assigns, overwritten state, and event-order assumptions.

Step 3: Collection and Render Checks

Audit:

• Large list assigns that should be streams
• Unbounded assign growth
• Repeated expensive computations on every render
• Temporary assigns where applicable

Step 4: Resolution Pattern

Apply the smallest safe fix:

• Move state to the correct callback boundary
• Use streams for collection updates
• Isolate side effects from render flow
• Add regression test for the exact failure timeline

Output Expectations

Return:

• Reproduction timeline
• Root-cause callback/state mismatch
• Concrete patch strategy
• Regression test scope