如何使用bit64功能將data.table :: fread包裝在您自己的包中？

Question

我有一個包含一個從data.table調用fread的函數的包。 data.table在其DESCRIPTION文件的Suggests字段中有bit64包，它使fread能夠將大整數導入為integer64而不是numeric 。 我的包中默認需要此功能。

這是一個可重現的例子，在R 3.1.3下（早期版本沒有這個問題）。

---

嘗試1

Vectorize(dir.create)(c("test", "test/R", "test/man"))

cat(
  "Package: test
Title: Test pkg
Description: Investigate how to use suggested package
Version: 0.0-1
Date: 2015-03-10
Author: Richie Cotton
Maintainer: Richie Cotton <a@b.com>
Imports: data.table
Suggests: bit64
License: Unlimited
",
  file = "test/DESCRIPTION"
)

cat(
  "#' Read data
#' 
#' Wrapper to \\code{fread} that loads bit64 first
#' @param ... Passed to fread.
#' @return A data frame of uniformly distributed random numbers and their index.
#' @importFrom data.table fread
#' @export
read_data <- function(...)
{
  library(bit64)
  fread(...)
}",
  file = "test/R/read_data.R"
)

當我運行R CMD check ，

library(roxygen2)
library(devtools)
roxygenize("test")
check("test")

我得到以下NOTE ：

* checking dependencies in R code ... NOTE
'library' or 'require' call to 'bit64' in package code.
Please use :: or requireNamespace() instead.
See section 'Suggested packages' in the 'Writing R Extensions' manual.

---

嘗試2

文檔建議用requireNamespace替換library 。 這將檢查包是否存在，但不會將其加載到R的搜索路徑中。

如果我將read_data的定義更新為：

read_data <- function(...)
{
  if(!requireNamespace('bit64')) 
  {
    warning('bit64 not available.')
  }
  fread(...)
}

然后R CMD check運行順利，但由於bit64現在沒有加載， fread沒有能力讀取長整數。

---

嘗試3

如果我更改了DESCRIPTION以便bit64位於Depends部分（而不是Suggests ，並將read_data保留為嘗試2，或將其簡化為

read_data <- function(...)
{
  fread(...)
}

然后R CMD check給出NOTE ：

* checking dependencies in R code ... NOTE
Package in Depends field not imported from: 'bit64'
  These packages need to be imported from (in the NAMESPACE file)
  for when this namespace is loaded but not attached.

在這種情況下，我不太確定我應該導入什么。

---

嘗試4

如果我在Depends部分保留bit64 ，並使用read_data的原始定義，

read_data <- function(...)
{
  library(bit64)
  fread(...)
}

然后R CMD check給出NOTE ：

* checking dependencies in R code ... NOTE
'library' or 'require' call to 'bit64' which was already attached by Depends.
Please remove these calls from your code.
Package in Depends field not imported from: 'bit64'

---

我覺得應該有一些DESCRIPTION和函數定義的神奇組合，它給我bit64功能並干凈地傳遞R CMD check ; 我只是看不出我錯過了什么。

我怎樣才能做到這一點？

Answer 1

嘗試3最接近; 我只是在roxygen文檔中需要一個額外的@import bit64 。

Vectorize(dir.create)(c("test", "test/R", "test/man"))

cat(
  "Package: test
Title: Test pkg
Description: Investigate how to use suggested package
Version: 0.0-1
Date: 2015-03-10
Author: Richie Cotton
Maintainer: Richie Cotton <a@b.com>
Depends: bit64
Imports: data.table
License: Unlimited
",
  file = "test/DESCRIPTION"
)

cat(
  "#' Read data
#' 
#' Wrapper to \\code{fread} that loads bit64 first
#' @param ... Passed to fread.
#' @return A data frame of uniformly distributed random numbers and their index.
#' @import bit64
#' @importFrom data.table fread
#' @export
read_data <- function(...)
{
  fread(...)
}",
  file = "test/R/read_data.R"
)