Should there be a cli_suppress function or similar?

[jimhester]

I think it would be somewhat common for users to want to suppress cli messages for a given chunk of code. Something like this maybe?

cli_suppress <- function(expr) {
  withCallingHandlers(
    expr,
    cli_message = function(c) {
      invokeRestart("cli_message_handled")
    }
  )
}

[gaborcsardi]

cli uses message(), suppressMessages() is fine, no?

> suppressMessages(cli::cli_text("foobar"))
> 

[jimhester]

yes, but that is a pretty heavy hammer, part of the appeal is to suppress only a specific class of message.

Also I don't actually understand why suppressMessages() is even working, since cli_message doesn't actually inherit from message

str(tryCatch(cli::cli_text("foobar"), condition = identity))
#> List of 4
#>  $ message: chr "cli message text"
#>  $ type   : chr "text"
#>  $ args   :List of 1
#>   ..$ text:List of 2
#>   .. ..$ str   : 'glue' chr "foobar"
#>   .. ..$ values:<environment: 0x101acc770> 
#>   .. ..- attr(*, "class")= chr "cli_glue_delay"
#>  $ pid    : int 9035
#>  - attr(*, "class")= chr [1:3] "cli_message" "callr_message" "condition"

^{Created on 2020-06-10 by the reprex package (v0.3.0)}

[gaborcsardi]

IDK, I am not entirely convinced that it is useful to suppress only messages that are coming from cli. E.g. just because a package switches from message() to cli_*() the messages would be suppressed. Or the other way.

I think it is more useful to suppress messages from a certain package, or from a function, or of a certain type, e.g. download messages, or log messages, etc.

But anyway, I can add another class to the final output messages, and then you can use the new suppressMessages(..., "cliMessage") or withCallingHandlers(..., cliMessage = function(x) tryInvokeRestart("muffleMessage")) to suppress them.

[jimhester]

There is already a cli_message class in the object, but there would need to be a message as well for suppressMessages(..., "cli_message") to work, e.g. it currently does not.

suppressMessages(cli::cli_text("foo"), class = "cli_message")
#> foo

^{Created on 2020-06-10 by the reprex package (v0.3.0)}

Even if you do add the message class I am pretty sure withCallingHandlers(..., cliMessage = function(x) tryInvokeRestart("muffleMessage")) won't work, as there won't be any muffleMessage restart registered, that is why I had to use the cli_message_handled restart above.

[gaborcsardi]

OK, I added a cliMessage class, so this works now:

> suppressMessages(cli_text("foo"), "cliMessage")
> 

I'll leave this issue open, because I still want to add a note to the docs, I'll document it together with #157, I think that'll give a nice way to suppress certain types of messages.

[gaborcsardi]

@jimhester Don't get caught up (no pun intended) with the cli_message conditions, that's an internal thing, and the final output is generated with message (and now also cliMessage) conditions. Hence the fix.

[gaborcsardi]

You can now catch/suppress the cliMessage conditions, so I am closing this.

[halldc]

Hi @gaborcsardi - I found the vignette confusing on this point. I've been trying suppressMessages(expr, classes = "cli_message") without luck before discovering this issue. Perhaps we could mention the cliMessage class here:

cli/vignettes/semantic-cli.Rmd

Lines 427 to 443 in 154f321

	# CLI messages
	All `cli_*()` functions are implemented using standard R conditions.
	For example a `cli_alert()` call emits an R condition with class `cli_message`.
	These messages can be caught, muffled, transfered from a subprocess to the main R process.
	When a cli function is called:
	1. cli throws a `cli_message` condition.
	2. If this condition is caught and muffled (via the `cli_message_handled` restart), then nothing else happens.
	3. Otherwise the `cli.default_handler` option is checked and if this is a function, then it is called with the message.
	4. If the `cli.default_handler` option is not set, or it is not a function, the default cli handler is called, which shows the text, alert, heading, etc. on the screen, using the standard R `message()` function.
	```{asciicast}
	tryCatch(cli_h1("Heading"), cli_message = function(x) x)
	suppressMessages(cli_text("Not shown"))
	```