tidyr 1.2.0

Pivoting

• pivot_wider() gains new names_expand and id_expand arguments for turning
  implicit missing factor levels and variable combinations into explicit ones.
  This is similar to the drop argument from spread() (#770).

• pivot_wider() gains a new names_vary argument for controlling the
  ordering when combining names_from values with values_from column names
  (#839).

• pivot_wider() gains a new unused_fn argument for controlling how to
  summarize unused columns that aren't involved in the pivoting process (#990,
  thanks to @mgirlich for an initial implementation).

• pivot_longer()'s names_transform and values_transform arguments now
  accept a single function which will be applied to all of the columns
  (#1284, thanks to @smingerson for an initial implementation).

• pivot_longer()'s names_ptypes and values_ptypes arguments now
  accept a single empty ptype which will be applied to all of the columns
  (#1284).

Nesting

• unnest() and unchop()'s ptype argument now accepts a single empty
  ptype which will be applied to all cols (#1284).

• unpack() now silently skips over any non-data frame columns specified by
  cols. This matches the existing behavior of unchop() and unnest()
  (#1153).

Rectangling

• unnest_wider() and unnest_longer() can now unnest multiple columns at
  once (#740).

• unnest_longer()'s indices_to and values_to arguments now accept
  a glue specification, which is useful when unnesting multiple columns.

• For hoist(), unnest_longer(), and unnest_wider(), if a ptype is
  supplied, but that column can't be simplified, the result will be a list-of
  column where each element has type ptype (#998).

• unnest_wider() gains a new strict argument which controls whether or not
  strict vctrs typing rules should be applied. It defaults to FALSE for
  backwards compatibility, and because it is often more useful to be lax
  when unnesting JSON, which doesn't always map one-to-one with R's types
  (#1125).

• hoist(), unnest_longer(), and unnest_wider()'s simplify argument now
  accepts a named list of TRUE or FALSE to control simplification on a per
  column basis (#995).

• hoist(), unnest_longer(), and unnest_wider()'s transform argument now
  accepts a single function which will be applied to all components (#1284).

• hoist(), unnest_longer(), and unnest_wider()'s ptype argument now
  accepts a single empty ptype which will be applied to all components (#1284).

Grids

• complete() gains a new explicit argument for limiting fill to only
  implicit missing values. This is useful if you don't want to fill in
  pre-existing missing values (#1270).

• complete() gains a grouped data frame method. This generates a more correct
  completed data frame when groups are involved (#396, #966).

• complete() and expand() no longer allow you to complete or expand on a
  grouping column. This was never well-defined since completion/expansion on a
  grouped data frame happens "within" each group and otherwise has the
  potential to produce erroneous results (#1299).

Missing values

• drop_na(), replace_na(), and fill() have been updated to utilize vctrs.
  This means that you can use these functions on a wider variety of column
  types, including lubridate's Period types (#1094), data frame columns, and
  the rcrd type from vctrs.

• replace_na() no longer allows the type of data to change when the
  replacement is applied. replace will now always be cast to the type of
  data before the replacement is made. For example, this means that using a
  replacement value of 1.5 on an integer column is no longer allowed.
  Similarly, replacing missing values in a list-column must now be done with
  list("foo") rather than just "foo".

• replace_na() no longer replaces empty atomic elements in list-columns
  (like integer(0)). The only value that is replaced in a list-column is
  NULL (#1168).

• drop_na() no longer drops empty atomic elements from list-columns
  (like integer(0)). The only value that is dropped in a list-column is
  NULL (#1228).

Bug fixes and minor improvements

General

• @mgirlich is now a tidyr author in recognition of his significant and
  sustained contributions.

• All lazyeval variants of tidyr verbs have been soft-deprecated. Expect them
  to move to the defunct stage in the next minor release of tidyr (#1294).

• any_of() and all_of() from tidyselect are now re-exported (#1217).

• dplyr >= 1.0.0 is now required.

Pivoting

• pivot_wider() now gives better advice about how to identify duplicates when
  values are not uniquely identified (#1113).

• pivot_wider() now throws a more informative error when values_fn doesn't
  result in a single summary value (#1238).

• pivot_wider() and pivot_longer() now generate more informative
  errors related to name repair (#987).

• pivot_wider() now works correctly when values_fill is a data frame.

• pivot_wider() no longer accidentally retains values_from when pivoting
  a zero row data frame (#1249).

• pivot_wider() now correctly handles the case where an id column name
  collides with a value from names_from (#1107).

• pivot_wider() and pivot_longer() now both check that the spec columns
  .name and .value are character vectors. Additionally, the .name
  column must be unique (#1107).

• pivot_wider()'s names_from and values_from arguments are now
  required if their default values of name and value don't correspond to
  columns in data. Additionally, they must identify at least 1 column
  in data (#1240).

• pivot_wider()'s values_fn argument now correctly allows anonymous
  functions (#1114).

• pivot_wider_spec() now works correctly with a 0-row data frame and a spec
  that doesn't identify any rows (#1250, #1252).

• pivot_longer()'s names_ptypes argument is now applied after
  names_transform for consistency with the rectangling functions
  (i.e. hoist()) (#1233).

• check_pivot_spec() is a new developer facing function for validating a pivot
  spec argument. This is only useful if you are extending pivot_longer() or
  pivot_wider() with new S3 methods (#1087).

Nesting

• The nest() generic now avoids computing on .data, making it more
  compatible with lazy tibbles (#1134).

• The .names_sep argument of the data.frame method for nest() is now
  actually used (#1174).

• unnest()'s ptype argument now works as expected (#1158).

• unpack() no longer drops empty columns specified through cols (#1191).

• unpack() now works correctly with data frame columns containing 1 row but
  0 columns (#1189).

• chop() now works correctly with data frames with 0 rows (#1206).

• chop()'s cols argument is no longer optional. This matches the
  behavior of cols seen elsewhere in tidyr (#1205).

• unchop() now respects ptype when unnesting a non-list column (#1211).

Rectangling

• hoist() no longer accidentally removes elements that have duplicated names
  (#1259).

Grids

• The grouped data frame methods for complete() and expand() now move the
  group columns to the front of the result (in addition to the columns you
  completed on or expanded, which were already moved to the front). This should
  make more intuitive sense, as you are completing or expanding "within" each
  group, so the group columns should be the first thing you see (#1289).

• complete() now applies fill even when no columns to complete are
  specified (#1272).

• expand(), crossing(), and nesting() now correctly retain NA values of
  factors (#1275).

• expand_grid(), expand(), nesting(), and crossing() now silently
  apply name repair to automatically named inputs. This avoids a number of
  issues resulting from duplicate truncated names
  (#1116, #1221, #1092, #1037, #992).

• expand_grid(), expand(), nesting(), and crossing() now allow
  columns from unnamed data frames to be used in expressions after that
  data frame was specified, like expand_grid(tibble(x = 1), y = x). This
  is more consistent with how tibble() behaves.

• expand_grid(), expand(), nesting(), and crossing() now work
  correctly with data frames containing 0 columns but >0 rows (#1189).

• expand_grid(), expand(), nesting(), and crossing() now return a 1
  row data frame when no inputs are supplied, which is more consistent with
  prod() == 1L and the idea that computations involving the number of
  combinations computed from an empty set should return 1 (#1258).

Missing values

• drop_na() no longer drops missing values from all columns when a tidyselect
  expression that results in 0 columns being selected is used (#1227).

• fill() now treats NaN like any other missing value (#982).