refactor: remove dead m_dsq client-side relay from MessageProcessingResult

[UdjinM6]

Issue being fixed or feature implemented

Client-side DSQ relay was removed in #7070 but the m_dsq field and its population in CCoinJoinClientQueueManager::ProcessMessage were left behind as dead code. The network has been running without client-side DSQ relay with no issues since masternodes handle DSQ propagation through their own CCoinJoinServer::ProcessDSQUEUE path.

Alternative to #7227

What was done?

Remove the dead code and fix transitive include dependencies that were masked by msg_result.h pulling in coinjoin/coinjoin.h. This also resolves two circular dependency chains that went through that link.

How Has This Been Tested?

Breaking Changes

n/a

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

[github-actions]

This pull request has conflicts, please rebase.

[github-actions]

⚠️ Potential Merge Conflicts Detected

This PR has potential conflicts with the following open PRs:

• refactor: remove dependencies of CInstantSendManager on mempool, signer, chainstate #7178 - refactor: remove dependencies of CInstantSendManager on mempool, signer, chainstate

Please coordinate with the authors of these PRs to avoid merge conflicts.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 74a0d712-641f-4551-b6d3-78ecabdbed1c

📥 Commits

Reviewing files that changed from the base of the PR and between 32fa1a8 and d142fc8.

📒 Files selected for processing (6)

• src/coinjoin/client.cpp
• src/instantsend/net_instantsend.h
• src/instantsend/signing.h
• src/msg_result.h
• src/rpc/quorums.cpp
• test/lint/lint-circular-dependencies.py

💤 Files with no reviewable changes (2)

• src/coinjoin/client.cpp
• test/lint/lint-circular-dependencies.py

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Walkthrough

The pull request removes the m_dsq field from the MessageProcessingResult struct and eliminates code that populates it in CCoinJoinClientQueueManager::ProcessMessage. The empty() method is updated to no longer reference this removed field. Forward declarations and header includes are added to reduce coupling and resolve circular dependencies. The circular dependency test expectations are updated to reflect two resolved dependency cycles involving msg_result, coinjoin, spork, chainlock, and instantsend modules.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: removing the dead m_dsq field from MessageProcessingResult in the client-side DSQ relay refactoring.
Description check	✅ Passed	The description is directly related to the changeset, explaining the removal of dead code (m_dsq field and its population) and the resolution of circular dependencies.

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[UdjinM6]

⏺ DSQ Relay Flow (post-#7070, current network behavior)

  ┌─────────────────────────────────────────────────────────────────────┐
  │                    MASTERNODE MESH (server path)                    │
  │                                                                     │
  │  ┌──────────────┐    PeerRelayDSQ()    ┌──────────────┐             │
  │  │ Originating  │────────────────────▶ │ Masternode B │             │
  │  │ Masternode A │                      │              │             │
  │  │              │    CCoinJoinServer:: │  ProcessDSQ  │             │
  │  │ Creates DSQ  │    ProcessDSQUEUE()  │  ──────────  │             │
  │  │ Signs w/ BLS │                      │ Validates    │             │
  │  └──────┬───────┘                      │ Stores queue │             │
  │         │                              │ Relays onward│             │
  │         │ PeerRelayDSQ()               └──────┬───────┘             │
  │         │                                     │                     │
  │         ▼                                     │ PeerRelayDSQ()      │
  │  ┌──────────────┐                             ▼                     │
  │  │ Masternode C │◀──── PeerRelayDSQ() ──-┌──────────────┐           │
  │  │              │                        │ Masternode D │           │
  │  └──────┬───────┘                        └──────┬───────┘           │
  │         │                                       │                   │
  └─────────┼───────────────────────────────────────┼────────────────-──┘
            │                                       │
            │ SENDDSQUEUE                           │ SENDDSQUEUE
            │ (m_wants_dsq = INV/ALL)               │
            ▼                                       ▼
     ┌──────────────┐                         ┌──────────────┐
     │ Wallet Node  │                         │ Wallet Node  │
     │              │                         │              │
     │  CCoinJoinClient                       │ Processes    │
     │  QueueManager::                        │ DSQ locally  │
     │  ProcessMessage()                      │              │
     │  ─────────────                         │ Joins queue  │
     │  Validates DSQ                         │ if ready     │
     │  Stores in queue                       └──────────────┘
     │  ✗ NO RELAY (dead
     │    code removed)
     └──────────────┘

    ┌───────────────────────────────────────────────────────-┐
    │ Key distinction:                                       │
    │                                                        │
    │  Server path (MN→MN): CCoinJoinServer::ProcessDSQUEUE  │
    │    → calls PeerRelayDSQ() directly on PeerManager      │
    │    → full gossip propagation across MN mesh            │
    │                                                        │
    │  Client path (MN→Wallet): CCoinJoinClientQueueManager  │
    │    → processes DSQ locally (validation, queue storage) │
    │    → previously relayed via m_dsq → PostProcessMessage │
    │    → relay removed in #7070, dead code cleaned up now  │
    └──────────────────────────────────────────────────────-─┘

  Masternodes form the relay backbone — each one that receives a valid DSQ
  re-broadcasts it via PeerRelayDSQ(). Wallet nodes are leaf consumers:
  they receive DSQs from their masternode peers, validate and store them locally,
  but don't propagate further.

[thepastaclaw]

Code Review

Clean dead-code removal of the unused m_dsq field from MessageProcessingResult. PostProcessMessage never consumed m_dsq — DSQ relay is handled entirely through PeerRelayDSQ called from coinjoin/server.cpp. The transitive include fixes and two circular dependency chain removals are correct.

Reviewed commit: d142fc8

[PastaPastaPasta]

utACK d142fc8