topics.md
In pkgdown: Make Static HTML Documentation for a Package

bad inputs give informative warnings

Code
  t <- select_topics("x + ", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be valid R code
  x Not 'x + '
Code
  t <- select_topics("y", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be a known topic name or alias
  x Not 'y'
Code
  t <- select_topics("paste(1)", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be a known selector function
  x Not 'paste(1)'
  Caused by error in `paste()`:
  ! could not find function "paste"
Code
  t <- select_topics("starts_with", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be a known topic name or alias
  x Not 'starts_with'
Code
  t <- select_topics("1", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be a string or function call
  x Not '1'
Code
  t <- select_topics("starts_with('y')", topics, check = TRUE)
Condition
  Error in `select_topics()`:
  ! No topics matched in '_pkgdown.yml'. No topics selected.

can select by name or alias

Code
  select_topics("a4", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be a known topic name or alias
  x Not 'a4'
Code
  select_topics("c::a", topics)
Condition
  Error:
  ! In '_pkgdown.yml', topic must be a known topic name or alias
  x Not 'c::a'

an unmatched selection generates a warning

Code
  select_topics(c("a", "starts_with('unmatched')"), topics, check = TRUE)
Condition
  Error:
  ! In '_pkgdown.yml', topic must match a function or concept
  x Not 'starts_with(\'unmatched\')'