如何格式化多行 R 包消息？

Question

在开发 R 包时，我想使用 R 的 message() 或 warning() 函数为我的包用户生成输出。

有时这些消息可能会很长。我可以做到这一点（文本只是微不足道的例子）：

message("If you got to this point in the code, it means the matrix was empty. Calculation continues but you should consider re-evaluating an earlier step in the process")

很好...但是为了风格，我还希望我的 行代码少于 80 个字符，这样它们就可以很好地适应狭窄的屏幕，在 GitHub, 等。然后我可以使用 IDE 代码回流工具轻松地重新格式化我的消息，如果它发生变化。

所以我试试这个：

message("If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process")

这解决了我的代码标准 -- 它少于 80 个字符行并且可以按预期重排。但这会在我的消息输出中留下白色space，我也不想要：

If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process

所以我发现这个名为 strwrap() 的函数似乎可以解决问题：

message(strwrap("If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process"))

输出：

If you got to this point in the code, it means the matrix was empty. 
Calculation continues but you should considerre-evaluating an earlier 
step in the process

看起来不错——但它消除了 "consider" 和 "re-evaluating" 之间的 space，因为 space 是换行符。

另一种方法是在代码中将其分解成块：

message("If you got to this point in the code, it means ", 
"the matrix was empty. Calculation continues but you should consider ",
"re-evaluating an earlier step in the process")

这使得输出看起来是正确的，但是文本不能再用 IDE 等轻松地回流，因为它不是一个字符串，所以这对我来说在开发方面不起作用。

那么：我怎样才能制作出格式良好的消息，让我可以轻松地跨行编写消息？

我写过这个函数：

.nicemsg = function(...) {
    message(paste(strwrap(...), collapse="\n"))
}

是否有使用内置函数的更好方法，这样我就不必在我编写的每个 R 包中都包含此函数？

Answer 1

您可以通过在字符串中添加 \n 来强制换行。

message("If you got to this point in the code,\nit means the matrix was empty.\nCalculation continues but you should consider re-evaluating\nan earlier step in the process")
# If you got to this point in the code,
# it means the matrix was empty.
# Calculation continues but you should consider re-evaluating
# an earlier step in the process

Answer 2

使用来自 strwrap 的更多参数使这成为可能

message(strwrap(..., prefix = " ", initial = ""))

您可以通过调整参数顺序来提高可读性。我不确定这是否更好。

message(strwrap(prefix = " ", initial = "", 
  "If you got to this point in the code, it means 
the matrix was empty. Calculation continues but you should consider
 re-evaluating an earlier step in the process"))

或者，如果您喜欢包装它

tidymess <- function(..., prefix = " ", initial = ""){
  message(strwrap(..., prefix = prefix, initial = initial))
}

如何格式化多行 R 包消息？

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r