---
title: "Logging from R Packages"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Logging from R Packages}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r pkgchecks, echo = FALSE}
## check if other logger packages are available and exit if not
for (pkg in c('devtools')) {
    if (!requireNamespace(pkg, quietly = TRUE)) {
        warning(paste(pkg, 'package not available, so cannot build this vignette'))
        knitr::knit_exit()
    }
}
```

```{r setup, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

In this vignette I suppose that you are already familiar with [Customizing the format and destination of log records](https://daroczig.github.io/logger/articles/customize_logger.html) vignette, especially with the [Log namespaces](https://daroczig.github.io/logger/articles/customize_logger.html#log-namespaces) section.

So that your R package's users can suppress (or render with custom layout) the log messages triggered by your R package, it's wise to record all those log messages in a custom namespace. By default, if you are calling the `?log_level` function family from an R package after importing from the `logger` package, then `logger` will try to auto-guess the calling R package name and use that as the default namespace, see eg:

```{r}
library(logger)
devtools::load_all(system.file('demo-packages/logger-tester-package', package = 'logger'))
logger_tester_function(INFO, 'hi from tester package')
```

But if auto-guessing is not your style, then feel free to set your custom namespace (eg the name of your package) in all `?log_info` etc function calls and let your users know about how to suppress / reformat / redirect your log messages via `?log_threshold`, `?log_layout`, `?log_appender`.

Please note that setting the formatter function via `?log_formatter` should not be left to the R package end-users, as the log message formatter is specific to your logging calls, so that should be decided by the R package author. Feel free to pick any formatter function (eg `glue`, `sprintf`, `paste` or something else), and set that via `?log_formatter` when your R package is loaded. All other parameters of your `logger` will inherit from the `global` namespace -- set by your R package's end user.
