tests/testthat/_snaps/mutate.md

In dplyr: A Grammar of Data Manipulation

mutate() supports constants (#6056, #6305)

Code
  (expect_error(mutate(df, z = !!z)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `z = <int>`.
  Caused by error:
  ! Inlined constant `z` must be size 10 or 1, not 5.
Code
  (expect_error(mutate(group_by(df, g), z = !!z)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `z = <int>`.
  Caused by error:
  ! Inlined constant `z` must be size 10 or 1, not 5.
Code
  (expect_error(mutate(rowwise(df), z = !!z)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `z = <int>`.
  Caused by error:
  ! Inlined constant `z` must be size 10 or 1, not 5.

Code
  (expect_error(mutate(group_by(df, g), y = .env$y)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `y = .env$y`.
  i In group 1: `g = 1`.
  Caused by error:
  ! `y` must be size 5 or 1, not 10.
Code
  (expect_error(mutate(rowwise(df), y = .env$y)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `y = .env$y`.
  i In row 1.
  Caused by error:
  ! `y` must be size 1, not 10.
  i Did you mean: `y = list(.env$y)` ?

can't overwrite column active bindings (#6666)

Code
  mutate(df, y = {
    x <<- 2
    x
  })
Condition
  Error in `mutate()`:
  i In argument: `y = { ... }`.
  Caused by error:
  ! unused argument (base::quote(2))

Code
  mutate(df, .by = g, y = {
    x <<- 2
    x
  })
Condition
  Error in `mutate()`:
  i In argument: `y = { ... }`.
  i In group 1: `g = 1`.
  Caused by error:
  ! unused argument (base::quote(2))

Code
  mutate(gdf, y = {
    x <<- 2
    x
  })
Condition
  Error in `mutate()`:
  i In argument: `y = { ... }`.
  i In group 1: `g = 1`.
  Caused by error:
  ! unused argument (base::quote(2))

can't share local variables across expressions (#6666)

Code
  mutate(df, x2 = {
    foo <- x
    x
  }, y2 = {
    foo
  })
Condition
  Error in `mutate()`:
  i In argument: `y2 = { ... }`.
  Caused by error:
  ! object 'foo' not found

rowwise mutate un-lists existing size-1 list-columns (#6302)

Code
  mutate(df, y = x)
Condition
  Error in `mutate()`:
  i In argument: `y = x`.
  i In row 2.
  Caused by error:
  ! `y` must be size 1, not 2.
  i Did you mean: `y = list(x)` ?

catches .by with grouped-df

Code
  mutate(gdf, .by = x)
Condition
  Error in `mutate()`:
  ! Can't supply `.by` when `.data` is a grouped data frame.

catches .by with rowwise-df

Code
  mutate(rdf, .by = x)
Condition
  Error in `mutate()`:
  ! Can't supply `.by` when `.data` is a rowwise data frame.

mutate() deals with 0 groups (#5534)

Code
  mutate(df, y = max(x))
Condition
  Warning:
  There was 1 warning in `mutate()`.
  i In argument: `y = max(x)`.
  Caused by warning in `max()`:
  ! no non-missing arguments to max; returning -Inf
Output
  # A tibble: 0 x 2
  # Groups:   x [0]
  # i 2 variables: x <dbl>, y <dbl>

mutate() give meaningful errors

Code
  tbl <- tibble(x = 1:2, y = 1:2)
  (expect_error(mutate(tbl, y = NULL, a = sum(y))))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `a = sum(y)`.
  Caused by error:
  ! object 'y' not found
Code
  (expect_error(mutate(group_by(tbl, x), y = NULL, a = sum(y))))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `a = sum(y)`.
  i In group 1: `x = 1`.
  Caused by error:
  ! object 'y' not found
Code
  (expect_error(mutate(tibble(x = 1), y = mean)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `y = mean`.
  Caused by error:
  ! `y` must be a vector, not a function.
Code
  df <- tibble(g = c(1, 1, 2, 2, 2), x = 1:5)
  (expect_error(mutate(df, out = env(a = 1))))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `out = env(a = 1)`.
  Caused by error:
  ! `out` must be a vector, not an environment.
Code
  (expect_error(mutate(group_by(df, g), out = env(a = 1))))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `out = env(a = 1)`.
  i In group 1: `g = 1`.
  Caused by error:
  ! `out` must be a vector, not an environment.
Code
  (expect_error(mutate(rowwise(df), out = rnorm)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `out = rnorm`.
  i In row 1.
  Caused by error:
  ! `out` must be a vector, not a function.
  i Did you mean: `out = list(rnorm)` ?
Code
  (expect_error(mutate(group_by(data.frame(x = rep(1:5, each = 3)), x), val = ifelse(
    x < 3, "foo", 2))))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `val = ifelse(x < 3, "foo", 2)`.
  Caused by error:
  ! `val` must return compatible vectors across groups.
  i Result of type <character> for group 1: `x = 1`.
  i Result of type <double> for group 3: `x = 3`.
Code
  (expect_error(mutate(group_by(tibble(a = 1:3, b = 4:6), a), if (a ==
  1) NULL else "foo")))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `if (a == 1) NULL else "foo"`.
  i In group 1: `a = 1`.
  Caused by error:
  ! `if (a == 1) NULL else "foo"` must return compatible vectors across groups.
  x Can't combine NULL and non NULL results.
Code
  (expect_error(mutate(group_by(tibble(a = 1:3, b = 4:6), a), if (a ==
  2) NULL else "foo")))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `if (a == 2) NULL else "foo"`.
  i In group 2: `a = 2`.
  Caused by error:
  ! `if (a == 2) NULL else "foo"` must return compatible vectors across groups.
  x Can't combine NULL and non NULL results.
Code
  (expect_error(mutate(data.frame(x = c(2, 2, 3, 3)), int = 1:5)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `int = 1:5`.
  Caused by error:
  ! `int` must be size 4 or 1, not 5.
Code
  (expect_error(mutate(group_by(data.frame(x = c(2, 2, 3, 3)), x), int = 1:5)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `int = 1:5`.
  i In group 1: `x = 2`.
  Caused by error:
  ! `int` must be size 2 or 1, not 5.
Code
  (expect_error(mutate(group_by(data.frame(x = c(2, 3, 3)), x), int = 1:5)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `int = 1:5`.
  i In group 1: `x = 2`.
  Caused by error:
  ! `int` must be size 1, not 5.
Code
  (expect_error(mutate(rowwise(data.frame(x = c(2, 2, 3, 3))), int = 1:5)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `int = 1:5`.
  i In row 1.
  Caused by error:
  ! `int` must be size 1, not 5.
  i Did you mean: `int = list(1:5)` ?
Code
  (expect_error(mutate(rowwise(tibble(y = list(1:3, "a"))), y2 = y)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `y2 = y`.
  i In row 1.
  Caused by error:
  ! `y2` must be size 1, not 3.
  i Did you mean: `y2 = list(y)` ?
Code
  (expect_error(mutate(data.frame(x = 1:10), y = 11:20, y = 1:2)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `y = 1:2`.
  Caused by error:
  ! `y` must be size 10 or 1, not 2.
Code
  (expect_error(mutate(tibble(a = 1), c = .data$b)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `c = .data$b`.
  Caused by error in `.data$b`:
  ! Column `b` not found in `.data`.
Code
  (expect_error(mutate(group_by(tibble(a = 1:3), a), c = .data$b)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `c = .data$b`.
  i In group 1: `a = 1`.
  Caused by error in `.data$b`:
  ! Column `b` not found in `.data`.
Code
  lazy <- (function(x) list(enquo(x)))
  res <- mutate(rowwise(tbl), z = lazy(x), .keep = "unused")
  (expect_error(eval_tidy(res$z[[1]])))
Output
  <error/rlang_error>
  Error:
  ! Obsolete data mask.
  x Too late to resolve `x` after the end of `dplyr::mutate()`.
  i Did you save an object that uses `x` lazily in a column in the `dplyr::mutate()` expression ?
Code
  (expect_error(mutate(tibble(), stop("{"))))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `stop("{")`.
  Caused by error:
  ! {

mutate() errors refer to expressions if not named

Code
  (expect_error(mutate(mtcars, 1:3)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `1:3`.
  Caused by error:
  ! `1:3` must be size 32 or 1, not 3.
Code
  (expect_error(mutate(group_by(mtcars, cyl), 1:3)))
Output
  <error/dplyr:::mutate_error>
  Error in `mutate()`:
  i In argument: `1:3`.
  i In group 1: `cyl = 4`.
  Caused by error:
  ! `1:3` must be size 11 or 1, not 3.

mutate() doesn't allow data frames with missing or empty names (#6758)

Code
  mutate(df1)
Condition
  Error in `mutate()`:
  ! Can't transform a data frame with `NA` or `""` names.

Code
  mutate(df2)
Condition
  Error in `mutate()`:
  ! Can't transform a data frame with missing names.

dplyr documentation built on Feb. 3, 2026, 9:08 a.m.