cnd-handlers.md
In rlang: Functions for Base Types and Core R and 'Tidyverse' Features

try_fetch() checks inputs

Code
  (expect_error(try_fetch(NULL, function(...) NULL)))
Output
  <error/rlang_error>
  Error in `try_fetch()`:
  ! `...` must be named with condition classes.

can rethrow from `try_fetch()`

Code
  err <- catch_error(try_fetch(f(), error = function(cnd) abort("bar", parent = cnd)))
  print(err)
Output
  <error/rlang_error>
  Error:
  ! bar
  Caused by error in `h()`:
  ! foo
  ---
  Backtrace:
       x
    1. +-rlang:::catch_error(...)
    2. | \-rlang::catch_cnd(expr, "error")
    3. |   +-rlang::eval_bare(...)
    4. |   +-base::tryCatch(...)
    5. |   | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
    6. |   |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
    7. |   |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
    8. |   \-base::force(expr)
    9. +-rlang::try_fetch(f(), error = function(cnd) abort("bar", parent = cnd))
   10. | +-base::tryCatch(...)
   11. | | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
   12. | |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
   13. | |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
   14. | \-base::withCallingHandlers(...)
   15. \-rlang (local) f()
   16.   \-rlang (local) g()
   17.     \-rlang (local) h()
Code
  print(err, simplify = "none")
Output
  <error/rlang_error>
  Error:
  ! bar
  Caused by error in `h()`:
  ! foo
  ---
  Backtrace:
       x
    1. +-rlang:::catch_error(...)
    2. | \-rlang::catch_cnd(expr, "error")
    3. |   +-rlang::eval_bare(...)
    4. |   +-base::tryCatch(...)
    5. |   | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
    6. |   |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
    7. |   |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
    8. |   \-base::force(expr)
    9. +-rlang::try_fetch(f(), error = function(cnd) abort("bar", parent = cnd))
   10. | +-base::tryCatch(...)
   11. | | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
   12. | |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
   13. | |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
   14. | \-base::withCallingHandlers(...)
   15. \-rlang (local) f()
   16.   \-rlang (local) g()
   17.     \-rlang (local) h()
Code
  err <- catch_error(high1(chain = TRUE))
  print(err)
Output
  <error/rlang_error>
  Error in `high3()`:
  ! bar
  Caused by error in `h()`:
  ! foo
  ---
  Backtrace:
       x
    1. +-rlang:::catch_error(high1(chain = TRUE))
    2. | \-rlang::catch_cnd(expr, "error")
    3. |   +-rlang::eval_bare(...)
    4. |   +-base::tryCatch(...)
    5. |   | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
    6. |   |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
    7. |   |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
    8. |   \-base::force(expr)
    9. \-rlang (local) high1(chain = TRUE)
   10.   \-rlang (local) high2(...)
   11.     \-rlang (local) high3(...)
   12.       +-rlang::try_fetch(f(), error = function(cnd) abort("bar", parent = cnd))
   13.       | +-base::tryCatch(...)
   14.       | | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
   15.       | |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
   16.       | |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
   17.       | \-base::withCallingHandlers(...)
   18.       \-rlang (local) f()
   19.         \-rlang (local) g()
   20.           \-rlang (local) h()
Code
  print(err, simplify = "none")
Output
  <error/rlang_error>
  Error in `high3()`:
  ! bar
  Caused by error in `h()`:
  ! foo
  ---
  Backtrace:
       x
    1. +-rlang:::catch_error(high1(chain = TRUE))
    2. | \-rlang::catch_cnd(expr, "error")
    3. |   +-rlang::eval_bare(...)
    4. |   +-base::tryCatch(...)
    5. |   | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
    6. |   |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
    7. |   |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
    8. |   \-base::force(expr)
    9. \-rlang (local) high1(chain = TRUE)
   10.   \-rlang (local) high2(...)
   11.     \-rlang (local) high3(...)
   12.       +-rlang::try_fetch(f(), error = function(cnd) abort("bar", parent = cnd))
   13.       | +-base::tryCatch(...)
   14.       | | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
   15.       | |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
   16.       | |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
   17.       | \-base::withCallingHandlers(...)
   18.       \-rlang (local) f()
   19.         \-rlang (local) g()
   20.           \-rlang (local) h()
Code
  err <- catch_error(high1(chain = FALSE))
  print(err)
Output
  <error/rlang_error>
  Error in `high3()`:
  ! bar
  ---
  Backtrace:
       x
    1. +-rlang:::catch_error(high1(chain = FALSE))
    2. | \-rlang::catch_cnd(expr, "error")
    3. |   +-rlang::eval_bare(...)
    4. |   +-base::tryCatch(...)
    5. |   | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
    6. |   |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
    7. |   |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
    8. |   \-base::force(expr)
    9. \-rlang (local) high1(chain = FALSE)
   10.   \-rlang (local) high2(...)
   11.     \-rlang (local) high3(...)
   12.       +-rlang::try_fetch(f(), error = function(cnd) abort("bar", parent = NA))
   13.       | +-base::tryCatch(...)
   14.       | | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
   15.       | |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
   16.       | |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
   17.       | \-base::withCallingHandlers(...)
   18.       \-rlang (local) f()
   19.         \-rlang (local) g()
   20.           \-rlang (local) h()
Code
  print(err, simplify = "none")
Output
  <error/rlang_error>
  Error in `high3()`:
  ! bar
  ---
  Backtrace:
       x
    1. +-rlang:::catch_error(high1(chain = FALSE))
    2. | \-rlang::catch_cnd(expr, "error")
    3. |   +-rlang::eval_bare(...)
    4. |   +-base::tryCatch(...)
    5. |   | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
    6. |   |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
    7. |   |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
    8. |   \-base::force(expr)
    9. \-rlang (local) high1(chain = FALSE)
   10.   \-rlang (local) high2(...)
   11.     \-rlang (local) high3(...)
   12.       +-rlang::try_fetch(f(), error = function(cnd) abort("bar", parent = NA))
   13.       | +-base::tryCatch(...)
   14.       | | \-base (local) tryCatchList(expr, classes, parentenv, handlers)
   15.       | |   \-base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
   16.       | |     \-base (local) doTryCatch(return(expr), name, parentenv, handler)
   17.       | \-base::withCallingHandlers(...)
   18.       \-rlang (local) f()
   19.         \-rlang (local) g()
   20.           \-rlang (local) h()