zlog/cmd/lint/readme.md

Zerolog Lint

This is a basic linter that checks for missing log event finishers. Finds errors like: log.Error().Int64("userID": 5) - missing the Msg/Msgf finishers.

Problem

When using zerolog it's easy to forget to finish the log event chain by calling a finisher - the Msg or Msgf function that will schedule the event for writing. The problem with this is that it doesn't warn/panic during compilation and it's not easily found by grep or other general tools. It's even prominently mentioned in the project's readme, that:

It is very important to note that when using the zerolog chaining API, as shown above (log.Info().Msg("hello world"), the chain must have either the Msg or Msgf method call. If you forget to add either of these, the log will not occur and there is no compile time error to alert you of this.

Solution

A basic linter like this one here that looks for method invocations on zerolog.Event can examine the last call in a method call chain and check if it is a finisher, thus pointing out these errors.

Usage

Just compile this and then run it. Or just run it via go run command via something like go run cmd/lint/lint.go.

The command accepts only one argument - the package to be inspected - and 4 optional flags, all of which can occur multiple times. The standard synopsis of the command is:

lint [-finisher value] [-ignoreFile value] [-ignorePkg value] [-ignorePkgRecursively value] package

Flags

• finisher
  • specify which finishers to accept, defaults to Msg and Msgf
• ignoreFile
  • which files to ignore, either by full path or by go path (package/file.go)
• ignorePkg
  • do not inspect the specified package if found in the dependecy tree
• ignorePkgRecursively
  • do not inspect the specified package or its subpackages if found in the dependency tree

Drawbacks

As it is, linter can generate a false positives in a specific case. These false positives come from the fact that if you have a method that returns a zerolog.Event the linter will flag it because you are obviously not finishing the event. This will be solved in later release.