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From: Alan Grunwald <nospam.nurdglaw@gmail.com>
Newsgroups: comp.lang.tcl
Subject: Re: try... query
Date: Fri, 6 Dec 2024 20:12:49 +0000
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On 06/12/2024 17:59, Ralf Fassel wrote:
> * Alan Grunwald <nospam.nurdglaw@gmail.com>
> | proc allocateResources {} {
> |     set obj1 [Some_mechanism]
> |     try {
> |         set obj2 [Some_other_mechanism]
> |         try {
> |             do_various_other_stuff
> |         } on error {message errorDict} {
> |             $obj2 destroy
> |             return                                          \
> |                 -code error                                 \
> |                 -errorcode [dict get $errorDict -errorcode] \
> |                 -errorinfo [dict get $errorDict -errorinfo] \
> |                 $message
> |         }
> 
> As Harald pointed out, 'finally' is the way to go here (even if the
> "if exist" is clunky :-).
> 
> I just wanted to point out that you could use the errorDict directly, as in
> 
>    try {
>      ...
>    } on error {msg opts} {
>      ...
>      return -options $opts $msg
>    }
> 
> instead of extracting errorinfo and errorcode manually, and if I use
> that form, I get the expected behaviour:
> 
>      proc foo {} {
>          try {
>              puts "level 1"
>              try {
>                  puts "level 2"
>                  error "err level 2"
>              } on error {msg opts} {
>                  puts "error in level 2"
>                  return -options $opts $msg
>              }
>          } on error {msg opts} {
>              puts "error in level 1"
>              return -options $opts $msg
>          }
>      }
>      
>      % catch foo
>      level 1
>      level 2
>      error in level 2
>      error in level 1
>      1
>      
>      % set errorInfo
>      err level 2
>          while executing
>      "error "err level 2""
>          (procedure "foo" line 6)
>          invoked from within
>      "foo"
> 
> HTH
> R'

Thanks Ralf,

As I pointed out to Harald, deleting the objects in a finally clause is 
explicitly not what I want to do since I wish to return them if there 
are no errors. I believe that I need to propagate the error explicitly 
if I add an on error clause. I'll see what happens if I do return 
-options $errorDict $message rather than extracting and specifying 
-code, -errorcode and -errorinfo. I guess if would help if I could 
recall what issue emerged when I tried doing it that way in the past, 
but sadly...

Alan