parity(realtime): add copyBindings() method to RealtimeChannel [from supabase-js] #241

SDK Parity: C# implementation needed

A change was made in supabase-js that needs to be implemented in this repository for SDK parity.

Reference Implementation (supabase-js)

• Commit: 9b8b53dc
• PR: feat(realtime): add copyBindings functionality supabase-js#2197
• Module: realtime
• Type: new-feature

What Changed

New CopyBindings(other: RealtimeChannel) method on RealtimeChannel that copies all event bindings (subscriptions/callbacks) from another channel instance. Useful for reconnection scenarios.

Code Reference

copyBindings(other: RealtimeChannel) {
  if (this.joinedOnce) {
    throw new Error('cannot copy bindings into joined channel')
  }
  for (const kind in other.bindings) {
    for (const binding of other.bindings[kind]) {
      this._on(binding.type, binding.filter, binding.callback)
    }
  }
}

Implementation Guidance

Expected API Surface (C#)

public void CopyBindings(IRealtimeChannel other)
{
    // Throws InvalidOperationException if this channel already joined
    // Copies all postgres_changes, broadcast, presence bindings from other
}

Key Behaviors to Match

• Throws InvalidOperationException (or similar) if channel has already joined
• Copies all binding types: postgres_changes, broadcast, presence
• Copies filter and callback for each binding
• Source channel (other) is not modified

Acceptance Criteria

• CopyBindings() method added to RealtimeChannel
• Throws if channel already subscribed/joined
• All binding types (postgres_changes, broadcast, presence) are copied
• Source channel unaffected after copy
• Unit tests for happy path and error case

Context

• supabase-js version: v2.101.0
• Parity tracking: This issue was auto-generated by SDK parity analysis

Generated with Claude Code /sync-sdk-parity