Print In Production

ID

swift.print_in_production

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Best Practice

Language

Swift

Tags

best-practice, leftover-debug, logging

Description

Reports unqualified calls to print, debugPrint, dump, or NSLog. These bypass the application’s structured logging pipeline and are almost always leftover diagnostics.

print("loaded")                // FLAW
debugPrint(user)               // FLAW
dump(user)                     // FLAW
NSLog("status %@", state)      // FLAW

logger.info("loaded")          // OK — structured logger
os_log("loaded", type: .info)  // OK — os.log
Custom.print("hi")             // OK — namespaced, not the stdlib `print`

Rationale

print and friends write unstructured text to stdout/stderr with no log level, no subsystem/category, no privacy redaction, and no filtering. They are perfect for ad-hoc debugging during development and a liability in production binaries — they leak diagnostics into the device console (where users and crash collectors can read them), they bypass remote log shipping, and they slow hot paths since the format strings are evaluated unconditionally.

Remediation

Use Apple’s os.log or the Logger / os_log APIs (or swift-log in server-side projects) and pick an appropriate log level and privacy modifier:

import os
let logger = Logger(subsystem: "com.example.app", category: "loading")

logger.info("loaded \(user, privacy: .public)")

For purely local debugging, wrap calls in #if DEBUG so they are stripped from release builds:

#if DEBUG
print("loaded")
#endif

References