r语言 - 如何将 data.table::fread 包装在您自己的软件包中，具有 bit64 功能

Question

我有一个包，其中包含一个从data.table调用fread的函数。 data.table在其 DESCRIPTION 文件的"建议"字段中具有bit64包，这使fread能够将大整数导入为 integer64而不是numeric. 默认情况下，我的软件包中需要此功能。

这是 R 3.1.3 下的一个可重现的示例（早期版本没有此问题）。

---

尝试 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 <[e-mail]>
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"
)

当我运行R CMD check时，

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.

---

尝试 2

文档建议将library替换为requireNamespace。 这将检查包是否存在，但不会将其加载到 R 的搜索路径上。

如果我将read_data的定义更新为：

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

然后R CMD check运行平稳，但由于bit64现在没有加载，fread没有读取长整数的能力。

---

尝试 3

如果我更改DESCRIPTION以便bit64位于Depends部分中（而不是Suggests，并像尝试 2 一样保留read_data，或将其简化为

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

然后R CMD check给出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.

我不太确定在这种情况下应该导入什么。

---

尝试 4

如果我bit64保留在Depends部分，并使用read_data的原始定义，

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

然后R CMD check给出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'

---

我觉得应该有一些DESCRIPTION和函数定义的神奇组合，为我提供bit64功能并干净利落地传递R CMD check;我只是看不到我错过了什么。

我该怎么做？

Answer 1

尝试 3 最接近;我只需要在 roxygen 文档中额外@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 <[e-mail]>
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"
)