Strange rebol bug: error needs a value

Question

When executing

do-file: func[file][
  if error? error: try [
    if (find [%.r %.cgi] (suffix? file)) [
      do file
    ]
  ][
    disarm error
    print ["error executing " file]
    input
  ]
]


foreach-file: func [
    "Perform function on each file in selected directory recursively"
    dir [file! url!] "Directory to look in"
    act [function!] "Function to perform (filename is unput to fuction)"
    /directory "Perform function also on directories"
    /local f files
][
    if not equal? last dir #"/" [
      dir: to-rebol-file join dir #"/"
    ]
    files: attempt [read dir]
    either none? files [return][
        foreach file files [
            f: join dir file
            either dir? f [
                either directory [
                    act f
                    foreach-file/directory f :act
                ][
                    foreach-file f :act
                ]
            ][act f]
        ]
    ]
]

feach-file %test/ :do-file

where %test would contain a file with just rebo header:

rebol []

The program stops with an error instead of disarming the error !

It doesn't give an error if the file contains something like

rebol []

test: context []

but it would fail again if it contains

rebol []

print ""

Why ?

Answer 1

A set word must be supplied with a value as illustrated by this console session:

a: func [] [#[unset!]] b: a ** Script Error: b needs a value ** Near: b: a

The solution is to use set/any instead of a set word.

? set USAGE: SET word value /any /pad

DESCRIPTION: Sets a word, block of words, or object to specified value(s). SET is a native value.

ARGUMENTS: word -- Word or words to set (Type: any-word block object) value -- Value or block of values (Type: any-type)

REFINEMENTS: /any -- Allows setting words to any value. /pad -- For objects, if block is too short, remaining words are set to NONE.

You can use something like:

if error? set/any 'error try [] [disarm error] == none

By the way, you can find the answers to many of your questions through the Rebol Mailing List Archive at http://www.rebol.org/ml-index.r.

Answer 2

do-file: func [ file
  /local err
][
  if error? set/any 'err try [
    if find [%.r %.cgi] suffix? file [
      do file
    ]
  ][
    print ["error executing " file]
    print mold disarm err
  ]
]

Those parentheses were unnecessary.

Here's an alternate style

do-file: func [file] [
    /local err
] [
    if error? set/any 'err try [
     all [
      find [%.r %.cgi] suffix? file
      do file
     ]
    ] [
     print ["error executing " file]
     print mold disarm err
    ]
]