在 R 中带有警告的函数中抑制、记录和返回值

Question

有一个有警告但不影响最终输出的函数。我想将警告捕获到日志中，在控制台上抑制警告消息并返回值。

fn1 <- function() {
    warning("this is a warning!")
    return(1)
}

我尝试了withCallingHandlers，但警告消息仍然打印出来，tryCatch 阻止返回值。例如，我使用message 假装保存到日志。

withCallingHandlers(expr = fn1(),
                    warning = function(w) {
                        message(paste0("saved to a file: ", w$message))
                        # write(w$message, "xxlocation")
                    }
)

输出

saved to a file: this is a warning!
[1] 1
Warning message:
In fn1() : this is a warning!

我可以使用重启来抑制警告，但我的返回值也被抑制了。和tryCatch很像：

withCallingHandlers(
    withRestarts(fn1(),
                 mufflewarn=function(msg) {
                     message(msg)
                 }),
    warning = function(w) {
        invokeRestart("mufflewarn", w$message)
    }
)

this is a warning!

有什么办法可以输出：

saved to a file: this is a warning!
[1] 1

Answer 1

原来解决方法很简单，只要在外面使用suppressWarnings就可以了：

suppressWarnings(withCallingHandlers(expr = fn1(),
                    warning = function(w) {
                        message(paste0("saved to a file: ", w$message))
                        # write(w$message, "xxlocation")
                    },
                    finally = function(x) suppressWarnings(x)
))

saved to a file: this is a warning!
[1] 1