自定义包抛出 Invalid .internal.selfref detected data.table 警告答案

【问题标题】：Custom package throwing Invalid .internal.selfref detected data.table warning自定义包抛出 Invalid .internal.selfref detected data.table 警告
【发布时间】：2019-06-24 00:57:01
【问题描述】：

请参阅此Stackoverflow question 以获取有关此问题的背景信息。基于来自@jangorecki 的cmets，我对**exploit_url.R** 进行了以下更改，如下所示：'

#' @export
#' @import data.table
exploit_url <- function(df, href, target, anchor, new_col) {
  return(df[, (new_col) := paste0("<a href='", df[[href]], "' target='", target, "'>", df[[anchor]], "</a>", "<br>")][, c(1, 3:6, 8)])
}

按照第 1 步和第 2 步操作，NAMESPACE 和 DESCRIPTION 中的所有内容都会得到处理。我收到一条警告消息，输出正确。

命名空间：

# Generated by roxygen2: do not edit by hand

import(data.table)

描述：

Package: poweR
Title: What the Package Does (One Line, Title Case)
Version: 0.0.0.9000
Authors@R: 
    person(given = "First",
           family = "Last",
           role = c("aut", "cre"),
           email = "first.last@example.com",
           comment = c(ORCID = "YOUR-ORCID-ID"))
Description: What the package does (one paragraph).
License: What license it uses
Encoding: UTF-8
LazyData: true
Imports: 
    data.table
RoxygenNote: 6.1.1.9000

输出：

新警告：

Warning message:
In `[.data.table`(df, , `:=`((new_col), paste0("<a href='", df[[href]],  :
  Invalid .internal.selfref detected and fixed by taking a (shallow) copy of the data.table so that := can add this new column by reference. At an earlier point, this data.table has been copied by R (or was created manually using structure() or similar). Avoid names<- and attr<- which in R currently (and oddly) may copy the whole data.table. Use set* syntax instead to avoid copying: ?set, ?setnames and ?setattr. If this message doesn't help, please report your use case to the data.table issue tracker so the root cause can be fixed or this message improved.

【问题讨论】：

标签： r r-package

【解决方案1】：

阅读警告消息后，我意识到这可能与我创建 data.table 的方式有关。进一步的研究让我找到了这个Stackoverflow link，它帮助我理解了我做错了什么。

我使用了以下代码：

# Create dataframe for testing
dput(head(cve_exploitdb[c(1:4),]))

根据帖子，我们应该避免将 data.table 复制到列表中。出于好奇，我在原始 data.table 上运行了 package 函数，它没有任何警告消息

【讨论】：