fix: implement single-flight connection handling and add tests for Wa…

[fairlighteth]

Summary

Reduce MaxListenersExceededWarning / register_error listeners added noise from the WalletConnect v2 path by fixing the app-side triggers instead of raising the listener limit.

This change covers the full repro we investigated:

• dedupe concurrent WalletConnect activate() calls while no session exists
• dedupe concurrent connectEagerly() calls
• preserve the existing-session path for normal WalletConnect network switching
• fully clean up transient pre-session WalletConnect providers during deactivate()
• stop BlockNumberProvider from polling/subscribing through the wallet transport and use the chain RPC provider instead
• retry failed WalletConnect activations through the correct per-chain cached connector
• reset failed pre-session WalletConnect connectors only after cleanup, while preserving live sessions on switch-chain errors
• add focused regression tests for concurrent activation, eager reconnect, transient cleanup, retry-chain preservation, and session-safe error handling

To Test

1. Open cowswap-frontend locally and connect with a WalletConnect-compatible wallet

• WalletConnect connection succeeds
• The console does not show MaxListenersExceededWarning: Possible EventEmitter memory leak detected. ... register_error listeners added

2. Cancel the WalletConnect flow a few times, click Try Again, then connect successfully

• Repeated cancel/retry attempts still work
• The warning does not appear after multiple canceled attempts followed by a successful connect
• The app does not open duplicate WalletConnect connection flows

3. Disconnect or switch away from WalletConnect, then reconnect with WalletConnect several times

• Reconnecting still works consistently
• The warning does not appear after repeated reconnect attempts
• The app keeps using the correct wallet state after reconnecting

4. Refresh the app with a remembered WalletConnect session

• Eager reconnect restores the session successfully
• The warning does not appear during app bootstrap

5. While an existing WalletConnect session is active, switch networks if that flow is available in your environment

• Network switching still works for an already connected WalletConnect session
• A rejected switch-chain attempt does not break the existing WalletConnect session
• Account and chain state stay in sync after the switch or failed switch

6. Leave the app open on a connected wallet and let block updates continue normally

• Block-based updates still work as expected
• No WalletConnect listener warning appears from background block polling

Background

The warning was not coming from CoW-owned frontend event emitters. The register_error listener is added inside WalletConnect's JSON-RPC WebSocket/provider stack.

The issue turned out to have multiple app-side triggers:

• overlapping WalletConnect bootstrap attempts from manual activation and eager reconnect
• transient pre-session WalletConnect instances not being cleaned up aggressively enough after failed/canceled attempts
• retry logic reusing or recreating the wrong per-chain WalletConnect connector after failures
• block polling going through the wallet provider instead of the chain RPC provider

This patch fixes those triggers directly rather than increasing the listener limit, which would only hide the underlying problem.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
cowfi	Ready	Preview	Mar 21, 2026 8:17pm
explorer-dev	Ready	Preview	Mar 21, 2026 8:17pm
swap-dev	Ready	Preview	Mar 21, 2026 8:17pm
widget-configurator	Ready	Preview	Mar 21, 2026 8:17pm

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
cosmos	Ignored		Mar 21, 2026 8:17pm
sdk-tools	Ignored	Preview	Mar 21, 2026 8:17pm

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[fairlighteth]

Closing this one as the current assessment is that it will be superseded/resolved by #7061

Re-open in case that isn't resolved after merging #7061