fix: keep EQ FluidSynth alive without a server

[ChrisTitusTech]

Follow-up to #1364 after live Fedora 44 validation exposed a FluidSynth lifecycle issue.

What changed

• Keep FluidSynth's local shell loop alive through a private mode-0600 FIFO instead of --server.
• Remove the FIFO alongside PID cleanup and reject unsafe runtime paths.
• Add mkfifo to installer and catalog prerequisites.

Root cause

FluidSynth 2.5.4 exits normally when --no-shell is used without server mode. Server mode keeps it alive but opens TCP port 9800 on all interfaces. The private FIFO preserves the process without a network listener.

Validation

• Live Fedora 44 installation against EverQuest Legends in native Lutris.
• Verified the ALSA EQ-Legends client and port while running.
• Verified no FluidSynth TCP listener.
• Verified watcher-driven shutdown at 65 seconds removed the process, PID file, FIFO, and launch tokens.
• sh -n, ShellCheck, checkbashisms, and shfmt pass for all three scripts.
• cargo fmt --all --check, cargo test --no-fail-fast --package linutil_core, cargo clippy -- -Dwarnings, cargo xtask docgen, and git diff --check pass.

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved reliability when starting and stopping the EverQuest Legends MIDI fix.
  • Added safer cleanup of temporary runtime resources during failures, recovery, and shutdown.
  • Added validation to prevent cleanup of invalid or unsafe paths.
  • The feature now checks that required system support is available before running.

Walkthrough

The EQ Legends MIDI hooks now use a secure runtime FIFO for FluidSynth standard input. Startup and stop paths remove the FIFO during normal shutdown and failure recovery. Requirement checks now require mkfifo.

Changes

EQ Legends MIDI FIFO lifecycle

Layer / File(s)	Summary
FIFO prerequisite checks core/tabs/gaming/eq-legends-midi.sh, core/tabs/gaming/tab_data.toml, core/tabs/gaming/eq-legends-midi-start.sh	The lifecycle checks and command precondition now require mkfifo.
Startup FIFO management core/tabs/gaming/eq-legends-midi-start.sh	The startup hook creates a mode-0600 FIFO, connects FluidSynth standard input to it, and removes it during recovery and readiness failures.
Stop-hook FIFO cleanup core/tabs/gaming/eq-legends-midi-stop.sh	The stop hook rejects symlinks and non-FIFO paths, then removes the FIFO across missing, invalid, stale, unrelated, and successful shutdown states.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant StartHook
  participant RuntimeFIFO
  participant FluidSynth
  participant MIDIReady
  StartHook->>RuntimeFIFO: Create and open FIFO
  StartHook->>FluidSynth: Launch with FIFO as standard input
  FluidSynth->>MIDIReady: Expose MIDI port
  StartHook->>RuntimeFIFO: Remove FIFO on failure or timeout

Loading

Possibly related PRs

• ChrisTitusTech/linutil#1364: Adds the related EQ Legends MIDI startup, stop, and setup behavior.

🚥 Pre-merge checks | ✅ 4 | ❌ 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 (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: keeping EQ FluidSynth alive without using server mode.
Description check	✅ Passed	The description directly explains the FIFO lifecycle change, safety cleanup, prerequisites, root cause, and validation.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch agent/eq-midi-local-lifecycle

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[ChrisTitusTech]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🎉

Reviewed commit: 9b95cb93c9

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[coderabbitai]

🧹 Nitpick comments (1)

core/tabs/gaming/eq-legends-midi-start.sh (1)

172-172: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Use command_exists for executable checks.

Line 172 uses command -v instead of the shared helper used by core/tabs/gaming/eq-legends-midi.sh Line 79.

Proposed change

-command -v mkfifo >/dev/null 2>&1 || fail "mkfifo is not installed"
+command_exists mkfifo || fail "mkfifo is not installed"

As per coding guidelines, use command_exists for executable checks.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@core/tabs/gaming/eq-legends-midi-start.sh` at line 172, Replace the direct
command -v check in the mkfifo validation with the shared command_exists helper,
preserving the existing fail message and behavior when mkfifo is unavailable.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@core/tabs/gaming/eq-legends-midi-start.sh`:
- Line 172: Replace the direct command -v check in the mkfifo validation with
the shared command_exists helper, preserving the existing fail message and
behavior when mkfifo is unavailable.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 3f971f1f-ec45-4137-a6b2-ba0f4a7de028

📥 Commits

Reviewing files that changed from the base of the PR and between 27b6683 and 42650c9.

📒 Files selected for processing (4)

• core/tabs/gaming/eq-legends-midi-start.sh
• core/tabs/gaming/eq-legends-midi-stop.sh
• core/tabs/gaming/eq-legends-midi.sh
• core/tabs/gaming/tab_data.toml

[ChrisTitusTech]

Reviewed the CodeRabbit nitpick on command_exists: eq-legends-midi-start.sh is a standalone extracted Lutris lifecycle hook and intentionally does not source common-script.sh. Its hook-local dependency checks consistently use command -v; replacing only the mkfifo check would call an undefined helper at runtime. No change is needed for that approved nitpick.