如何格式化多行R包消息？

Question

在開發R包時，我想用R的message()或warning()函數爲我的包用戶生成輸出。

有時這些消息可能很長。我能做到這一點（文本只是簡單的例子）：

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") 

大......但對於風格，我也希望我的行代碼少於80個字符，所以他們很好地適合在狹小的屏幕，在GitHub上等。然後，如果它發生變化，我可以使用IDE代碼重排工具輕鬆重新格式化我的消息。

所以我試試這個：

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") 

這解決了我的代碼標準 - 這是不到80層字符的線條和可迴流預期。但是，堅持在我的消息輸出的空白吧，我也不想：

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 

所以我發現了這個叫strwrap()方便的功能，這似乎解決的問題：

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")) 

輸出：

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 

看起來不錯 - 但它消除之間的「考慮」和「重新評估」，因爲這是空間在新行的空間。

另一種方法是將它分解成塊代碼：

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") 

這使得輸出看起來是正確的，但文本不再能夠輕鬆與IDE等迴流焊，因爲它不是一個字符串，所以這在開發方不適合我。

所以：我如何製作一個格式良好的消息，讓我可以輕鬆地跨行書寫消息？

我寫了這個功能：

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

是否有使用內置的，所以我不必須包括在每一個[R包我寫這篇文章的功能更好的辦法？

Answer 1

使用一對夫婦更多的參數從strwrap使這成爲可能

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

您可能能夠通過參數的順序播放，以提高可讀性。我不確定這是否更好。

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，如果你喜歡它包裹

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

Answer 2

您可以通過在字符串中添加\n來強制換行。

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