r - 你如何格式化多行 R 包消息？

Question

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

有时这些消息可能很长。我可以做到这一点(文字只是一个简单的例子):

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")

太棒了……但为了风格，我也想要我的 代码行数少于 80 个字符 ，因此它们非常适合在窄屏幕、GitHub 等中使用。然后我可以使用 IDE 代码重排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。但这在我的消息输出中保留了空格，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

所以我找到了这个名为 strwrap() 的方便的函数这似乎解决了问题:

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“考虑”和“重新评估”之间的空间，因为该空间位于换行符处。

另一种选择是在代码中将其分解为多个块:

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")

这使输出看起来正确，但文本不能再容易地使用 IDE 重排，等等，因为它不是一个字符串，所以这在开发方面对我不起作用。

那么:如何制作格式良好的消息，让我可以轻松地跨行编写消息？

我写了这个函数:

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

有没有更好的方法使用内置函数，这样我就不必在我编写的每个 R 包中都包含这个函数？

Answer 1

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的顺序来提高可读性。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，如果您更喜欢包装它

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