fix: UpdateContext skips Nop and zero-value loggers

[veeceey]

Summary

Fixes #643.

UpdateContext used pointer equality (l == disabledLogger) to detect disabled loggers. This only caught the package-level disabledLogger singleton returned by Ctx() when no logger is in the context, but missed loggers created via:

• zerolog.Nop() (returns a new disabled logger each time)
• Zero-value Logger{} (has nil writer)

When a shared Nop() logger was used from multiple goroutines, UpdateContext would proceed to mutate the context buffer concurrently, causing data races (confirmed with -race detector, reproduces 15 race warnings).

Changes

• log.go: Replace l == disabledLogger with l.w == nil || l.level == Disabled, consistent with how Logger.should() determines if logging is active
• log_test.go: Add TestUpdateContextOnNopLogger and TestUpdateContextOnZeroValueLogger to cover both missed cases

Test plan

• All existing tests pass (go test ./...)
• New tests verify UpdateContext is a no-op on Nop() loggers
• New tests verify UpdateContext is a no-op on zero-value loggers
• Data race no longer reproduces with go run -race on shared Nop() logger

[veeceey]

Hi @rs, friendly ping on this PR. It's been open for about 8 days without any review activity. Would appreciate any feedback when you have a moment. Happy to make adjustments if needed. Thank you!

[Copilot]

Pull request overview

This PR fixes UpdateContext incorrectly identifying “disabled” loggers using pointer equality, which missed Nop()-created loggers and zero-value Logger{} instances. The update aligns UpdateContext’s early-exit condition with the logger’s enabled/disabled semantics to prevent unintended context mutation (and associated data races) when logging is effectively disabled.

Changes:

• Update Logger.UpdateContext to skip updates when l.w == nil or l.level == Disabled.
• Add tests covering UpdateContext behavior on Nop() loggers and zero-value loggers.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
log.go	Updates UpdateContext to detect disabled/no-writer loggers without relying on pointer equality.
log_test.go	Adds regression tests ensuring UpdateContext is a no-op for Nop() and zero-value loggers.

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[IDisposable]

Might be better to add a method to log.go that encapsulates this and call here and in should()...

// detects if this is a disabled logger
func (l *Logger) disabled() bool {
   return l.w == nil || l.level <= Disabled
}

then here we do

if l.disabled() {
   return
}

and then should() starts with

// should returns true if the log event should be logged.
func (l *Logger) should(lvl Level) bool {
	if l.disabled() {
		return false
	}
...

[veeceey]

Good call — done. Extracted a disabled() method and updated both UpdateContext and should() to use it.

[IDisposable]