Partial matching when using named vector as faceting variable

Via larmarange/ggstats#126 I stumbled upon the fact that using a named vector as faceting variable emits an error for options(warn = 2, warnPartialMatchAttr = TRUE):

df <- list2DF(list(
  x = 1:2,
  y = 1:2,
  facet = setNames(
    factor(c("a", "b")),
    c("one", "two")
  )
))

ggplot2::ggplot(df, ggplot2::aes(x, y)) +
  ggplot2::geom_point() +
  ggplot2::facet_grid(rows = ggplot2::vars(facet))

Error in `attr()`:
! (converted from warning) partial argument match of 'n' to 'names'
Backtrace:
     ▆
  1. ├─base (local) `<fn>`(x)
  2. ├─ggplot2 (local) `print.ggplot2::ggplot`(x)
  3. │ ├─ggplot2::ggplot_build(x)
  4. │ └─ggplot2 (local) `ggplot_build.ggplot2::ggplot`(x)
  5. │   └─layout$setup(data, plot@data, plot@plot_env)
  6. │     └─ggplot2 (local) setup(..., self = self)
  7. │       └─self$facet$compute_layout(data, self$facet_params)
  8. │         └─ggplot2 (local) compute_layout(..., self = self)
  9. │           └─ggplot2:::id(base, drop = TRUE)
 10. │             └─ggplot2:::id_var(.variables[[1]], drop = drop)
 11. └─base::warning(cond)
 12.   └─base::withRestarts(...)
 13.     └─base (local) withOneRestart(expr, restarts[[1L]])
 14.       └─base (local) doWithOneRestart(return(expr), restart)

It may be necessary to pass exact = TRUE to attr().

Reproduce the example with options(warn = 2, warnPartialMatchAttr = TRUE), then start from the ggplot2:::id and ggplot2:::id_var calls shown in the backtrace. Trace the attr() lookup involved in the named faceting variable and add or update the relevant regression test if one is found. Done means the faceting example runs without a partial-match warning under those options.