Fix: keep internal runtime logs silent unless debug log is enabled

[guysmoilov]

User description

Summary

• make internal backend logger a no-op when no debug log file path is configured
• keep file-backed logging behavior unchanged when --debug-log or TMUX_MOBILE_DEBUG_LOG is set
• add backend unit tests covering silent default behavior and file logging behavior

Testing

• npx vitest run tests/backend/file-logger.test.ts
• npm test

Closes #37

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PR Type

Bug fix, Tests

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Description

• Replace console with no-op logger when debug log disabled

• Prevent internal runtime logs from appearing in stdout/stderr

• Add comprehensive unit tests for logger behavior

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Diagram Walkthrough

flowchart LR
  A["createLogger called"] --> B{"logFilePath provided?"}
  B -->|No| C["Return NOOP_LOGGER"]
  B -->|Yes| D["Return file-backed logger"]
  C --> E["Silent operation"]
  D --> F["Write to file"]

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File Walkthrough

	Relevant files
Bug fix	file-logger.ts Implement no-op logger for silent default behavior              src/backend/util/file-logger.ts Added NOOP_LOGGER constant with no-op implementations of log and error methods Changed createLogger to return NOOP_LOGGER instead of console when no log file path is provided Maintains existing file-backed logging behavior when debug log path is configured +6/-1
Tests	file-logger.test.ts Add unit tests for logger silent and file modes                    tests/backend/file-logger.test.ts Added new test file with comprehensive test suite for file logger Test verifies logger is silent when no debug log file is configured Test verifies logs are written to file with proper formatting when path is provided Uses vitest spies and temporary directories for isolated testing +36/-0

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Changes

src/backend/util/file-logger.ts

• Introduces a NOOP-style DEFAULT_LOGGER that silences logger.log while still delegating logger.error to console.error so errors continue to be reported to stderr by default.
• serialize now includes Error.stack when present (falls back to "name: message"), so error stack traces are preserved for file-backed logging.
• createLogger returns DEFAULT_LOGGER when no logFilePath is provided; when a path is provided behavior is unchanged (creates directories, appends timestamped lines with [INFO] or [ERROR]).

tests/backend/file-logger.test.ts (new file)

Adds tests covering:

1. Silent default behavior: logger.log is suppressed and logger.error is forwarded to console.error when no log file is configured.
2. File logging behavior: messages are written to the configured log file with expected formatting.
3. Error stack tracing: error.stack contents are written into the debug log.

No public API or exported-signature changes.

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📝 Walkthrough

Walkthrough

Modified the file logger to return a no-op logger when debug logging is disabled, silencing internal runtime logs by default. Added tests verifying silent mode operation and file-based logging functionality when a debug log path is configured.

Changes

Cohort / File(s)	Summary
File Logger Implementation src/backend/util/file-logger.ts	Introduced NOOP_LOGGER with no-op log and error methods. Modified createLogger to return NOOP_LOGGER instead of global console when logFilePath is undefined.
File Logger Tests tests/backend/file-logger.test.ts	Added test suite covering silent mode (no console output when debug log disabled) and file logging mode (logs written to file when debug log path provided).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Merge Conflict Detection	⚠️ Warning	❌ Merge conflicts detected (1 file): ⚔️ src/backend/util/file-logger.ts (content) These conflicts must be resolved before merging into main.	Resolve conflicts locally and push changes to this branch.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check	✅ Passed	The pull request successfully implements all acceptance criteria from issue #37: silent logging by default with NOOP_LOGGER, file-backed logging when configured, and comprehensive test coverage.
Out of Scope Changes check	✅ Passed	All changes directly address the requirements in issue #37. The modifications to file-logger.ts implement the silent default behavior, and the new test file validates both silent and file-logging modes.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feat/issue-37-debug-log-default

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[qodo-code-review]

PR Compliance Guide 🔍

Below is a summary of compliance checks for this PR:

Security Compliance
🟢	No security concerns identified No security vulnerabilities detected by AI analysis. Human verification advised for critical code.
Ticket Compliance
🟡	🎫 #37 🟢 By default, internal logger output is silent (no internal runtime/debug logs printed to stdout/stderr). ⚪ Providing --debug-log or TMUX_MOBILE_DEBUG_LOG writes internal logs to the configured file. Existing user-facing startup output (URLs/QR/password) remains unchanged.
Codebase Duplication Compliance
⚪	Codebase context is not defined Follow the guide to enable codebase context checks.
Custom Compliance
🟢	Generic: Meaningful Naming and Self-Documenting Code Objective: Ensure all identifiers clearly express their purpose and intent, making code self-documenting Status: Passed Learn more about managing compliance generic rules or creating your own custom rules
	Generic: Secure Error Handling Objective: To prevent the leakage of sensitive system information through error messages while providing sufficient detail for internal debugging. Status: Passed Learn more about managing compliance generic rules or creating your own custom rules
	Generic: Secure Logging Practices Objective: To ensure logs are useful for debugging and auditing without exposing sensitive information like PII, PHI, or cardholder data. Status: Passed Learn more about managing compliance generic rules or creating your own custom rules
	Generic: Security-First Input Validation and Data Handling Objective: Ensure all data inputs are validated, sanitized, and handled securely to prevent vulnerabilities Status: Passed Learn more about managing compliance generic rules or creating your own custom rules
⚪	Generic: Comprehensive Audit Trails Objective: To create a detailed and reliable record of critical system actions for security analysis and compliance. Status: Logging silenced by default: The logger now becomes a no-op when logFilePath is undefined, which could inadvertently disable audit-relevant logging if this logger is used for critical actions elsewhere in the system. Referred Code export const createLogger = ( logFilePath: string | undefined ): Pick<Console, "log" | "error"> => { if (!logFilePath) { return NOOP_LOGGER; } Learn more about managing compliance generic rules or creating your own custom rules
	Generic: Robust Error Handling and Edge Case Management Objective: Ensure comprehensive error handling that provides meaningful context and graceful degradation Status: Potentially swallowed errors: Returning NOOP_LOGGER causes all log/error calls to be silently dropped when logFilePath is not set, which may hide important runtime error context depending on how this logger is used. Referred Code const NOOP_LOGGER: Pick<Console, "log" | "error"> = { log: () => undefined, error: () => undefined }; Learn more about managing compliance generic rules or creating your own custom rules
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Compliance status legend

🟢 - Fully Compliant
🟡 - Partial Compliant
🔴 - Not Compliant
⚪ - Requires Further Human Verification
🏷️ - Compliance label

[qodo-code-review]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Prevent logging failures crashing Add a try...catch block around the fs.appendFileSync call to handle potential file system errors and prevent the application from crashing if logging fails. src/backend/util/file-logger.ts [33-38] const write = (level: "INFO" | "ERROR", values: unknown[]): void => { - const line = `${new Date().toISOString()} [${level}] ${values - .map((value) => serialize(value)) - .join(" ")}` - fs.appendFileSync(resolvedPath, `${line}\n`, "utf8"); + try { + const line = `${new Date().toISOString()} [${level}] ${values + .map((value) => serialize(value)) + .join(" ")}` + fs.appendFileSync(resolvedPath, `${line}\n`, "utf8"); + } catch (err) { + console.error("Failed to write log", err); + } }; [To ensure code accuracy, apply this suggestion manually] Suggestion importance[1-10]: 8 __ Why: This suggestion correctly identifies that an unhandled file system error in the logging function could crash the application and proposes adding a try...catch block, which significantly improves the logger's robustness.	Medium
General	Include error stack trace Modify the serialize function to include the stack trace when logging Error objects, which will provide more context for debugging. src/backend/util/file-logger.ts [9-12] const serialize = (value: unknown): string => { if (value instanceof Error) { - return `${value.name}: ${value.message}`; + return value.stack ?? `${value.name}: ${value.message}`; } // ... }; [To ensure code accuracy, apply this suggestion manually] Suggestion importance[1-10]: 7 __ Why: The suggestion improves debuggability by including the stack trace when logging Error objects, providing more context for troubleshooting.	Medium
	Make the shared logger object immutable Make the NOOP_LOGGER object immutable by wrapping it with Object.freeze() to prevent accidental runtime modifications. src/backend/util/file-logger.ts [4-7] -const NOOP_LOGGER: Pick<Console, "log" | "error"> = { +const NOOP_LOGGER: Pick<Console, "log" | "error"> = Object.freeze({ log: () => undefined, error: () => undefined -}; +}); Apply / Chat Suggestion importance[1-10]: 4 __ Why: The suggestion correctly recommends making the NOOP_LOGGER object immutable using Object.freeze(), which is a good defensive programming practice for shared constants, enhancing code robustness.	Low
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