Clarify status of reshape2 (#4908)

NEWS.md

@@ -697,7 +697,7 @@ has a better chance of working on Mac.
 
 7. Added a note to `?frank` clarifying that ranking is being done according to C sorting (i.e., like `forder`), [#2328](https:/Rdatatable/data.table/issues/2328). Thanks to @cguill95 for the request.
 
-8. Historically, `dcast` and `melt` were built as enhancements to `reshape2`'s own `dcast`/`melt`. We removed dependency on `reshape2` in v1.9.6 but maintained some backward compatibility. As that package has been deprecated since December 2017, we will begin to formally complete the split from `reshape2` by removing some last vestiges. In particular we now warn when redirecting to `reshape2` methods and will later error before ultimately completing the split; see [#3549](https:/Rdatatable/data.table/issues/3549) and [#3633](https:/Rdatatable/data.table/issues/3633). We thank the `reshape2` authors for their original inspiration for these functions, and @ProfFancyPants for testing and reporting regressions in dev which have been fixed before release.
+8. Historically, `dcast` and `melt` were built as enhancements to `reshape2`'s own `dcast`/`melt`. We removed dependency on `reshape2` in v1.9.6 but maintained some backward compatibility. As that package has been superseded since December 2017, we will begin to formally complete the split from `reshape2` by removing some last vestiges. In particular we now warn when redirecting to `reshape2` methods and will later error before ultimately completing the split; see [#3549](https:/Rdatatable/data.table/issues/3549) and [#3633](https:/Rdatatable/data.table/issues/3633). We thank the `reshape2` authors for their original inspiration for these functions, and @ProfFancyPants for testing and reporting regressions in dev which have been fixed before release.
 
 9. `DT[col]` where `col` is a column containing row numbers of itself to select, now suggests the correct syntax (`DT[(col)]` or `DT[DT$col]`), [#697](https:/Rdatatable/data.table/issues/697). This expands the message introduced in [#1884](https:/Rdatatable/data.table/issues/1884) for the case where `col` is type `logical` and `DT[col==TRUE]` is suggested.
 

R/fcast.R

@@ -17,8 +17,8 @@ dcast <- function(
  else {
  data_name = deparse(substitute(data))
  ns = tryCatch(getNamespace("reshape2"), error=function(e)
- stop("The dcast generic in data.table has been passed a ",class(data)[1L],", but data.table::dcast currently only has a method for data.tables. Please confirm your input is a data.table, with setDT(", data_name, ") or as.data.table(", data_name, "). If you intend to use a reshape2::dcast, try installing that package first, but do note that reshape2 is deprecated and you should be migrating your code away from using it."))
- warning("The dcast generic in data.table has been passed a ", class(data)[1L], " and will attempt to redirect to the reshape2::dcast; please note that reshape2 is deprecated, and this redirection is now deprecated as well. Please do this redirection yourself like reshape2::dcast(", data_name, "). In the next version, this warning will become an error.")
+ stop("The dcast generic in data.table has been passed a ",class(data)[1L],", but data.table::dcast currently only has a method for data.tables. Please confirm your input is a data.table, with setDT(", data_name, ") or as.data.table(", data_name, "). If you intend to use a reshape2::dcast, try installing that package first, but do note that reshape2 is superseded and is no longer actively developed."))
+ warning("The dcast generic in data.table has been passed a ", class(data)[1L], " and will attempt to redirect to the reshape2::dcast; please note that reshape2 is superseded and is no longer actively developed, and this redirection is now deprecated. Please do this redirection yourself like reshape2::dcast(", data_name, "). In the next version, this warning will become an error.")
  ns$dcast(data, formula, fun.aggregate = fun.aggregate, ..., margins = margins,
  subset = subset, fill = fill, value.var = value.var)
  }

R/fmelt.R

@@ -12,8 +12,8 @@ melt <- function(data, ..., na.rm = FALSE, value.name = "value") {
  } else {
  data_name = deparse(substitute(data))
  ns = tryCatch(getNamespace("reshape2"), error=function(e)
- stop("The melt generic in data.table has been passed a ",class(data)[1L],", but data.table::melt currently only has a method for data.tables. Please confirm your input is a data.table, with setDT(", data_name, ") or as.data.table(", data_name, "). If you intend to use a method from reshape2, try installing that package first, but do note that reshape2 is deprecated and you should be migrating your code away from using it."))
- warning("The melt generic in data.table has been passed a ", class(data)[1L], " and will attempt to redirect to the relevant reshape2 method; please note that reshape2 is deprecated, and this redirection is now deprecated as well. To continue using melt methods from reshape2 while both libraries are attached, e.g. melt.list, you can prepend the namespace like reshape2::melt(", data_name, "). In the next version, this warning will become an error.")
+ stop("The melt generic in data.table has been passed a ",class(data)[1L],", but data.table::melt currently only has a method for data.tables. Please confirm your input is a data.table, with setDT(", data_name, ") or as.data.table(", data_name, "). If you intend to use a method from reshape2, try installing that package first, but do note that reshape2 is superseded and is no longer actively developed."))
+ warning("The melt generic in data.table has been passed a ", class(data)[1L], " and will attempt to redirect to the relevant reshape2 method; please note that reshape2 is superseded and is no longer actively developed, and this redirection is now deprecated. To continue using melt methods from reshape2 while both libraries are attached, e.g. melt.list, you can prepend the namespace like reshape2::melt(", data_name, "). In the next version, this warning will become an error.")
  ns$melt(data, ..., na.rm=na.rm, value.name=value.name)
  }
  # nocov end

man/dcast.data.table.Rd

@@ -51,7 +51,7 @@ From \code{v1.9.4}, \code{dcast} tries to preserve attributes wherever possible.
 
 From \code{v1.9.6}, it is possible to cast multiple \code{value.var} columns and also cast by providing multiple \code{fun.aggregate} functions. Multiple \code{fun.aggregate} functions should be provided as a \code{list}, for e.g., \code{list(mean, sum, function(x) paste(x, collapse="")}. \code{value.var} can be either a character vector or list of length one, or a list of length equal to \code{length(fun.aggregate)}. When \code{value.var} is a character vector or a list of length one, each function mentioned under \code{fun.aggregate} is applied to every column specified under \code{value.var} column. When \code{value.var} is a list of length equal to \code{length(fun.aggregate)} each element of \code{fun.aggregate} is applied to each element of \code{value.var} column.
 
-Historical note: \code{dcast.data.table} was originally designed as an enhancement to \code{reshape2::dcast} in terms of computing and memory efficiency. \code{reshape2} has since been deprecated, and \code{dcast} has had a generic defined within \code{data.table} since \code{v1.9.6} in 2015, at which point the dependency between the packages became more etymological than programmatic. We thank the \code{reshape2} authors for the inspiration.
+Historical note: \code{dcast.data.table} was originally designed as an enhancement to \code{reshape2::dcast} in terms of computing and memory efficiency. \code{reshape2} has since been superseded in favour of \code{tidyr}, and \code{dcast} has had a generic defined within \code{data.table} since \code{v1.9.6} in 2015, at which point the dependency between the packages became more etymological than programmatic. We thank the \code{reshape2} authors for the inspiration.
 
 }
 \value{

man/melt.data.table.Rd

@@ -75,7 +75,7 @@ be coerced to \code{character} type. To get a \code{factor} column, set
 \code{value.factor = TRUE}. \code{melt.data.table} also preserves
 \code{ordered} factors.
 
-Historical note: \code{melt.data.table} was originally designed as an enhancement to \code{reshape2::melt} in terms of computing and memory efficiency. \code{reshape2} has since been deprecated, and \code{melt} has had a generic defined within \code{data.table} since \code{v1.9.6} in 2015, at which point the dependency between the packages became more etymological than programmatic. We thank the \code{reshape2} authors for the inspiration.
+Historical note: \code{melt.data.table} was originally designed as an enhancement to \code{reshape2::melt} in terms of computing and memory efficiency. \code{reshape2} has since been superseded in favour of \code{tidyr}, and \code{melt} has had a generic defined within \code{data.table} since \code{v1.9.6} in 2015, at which point the dependency between the packages became more etymological than programmatic. We thank the \code{reshape2} authors for the inspiration.
 
 }