NAME

Carp::Object - a replacement for Carp or Carp::Clan, object-oriented

SYNOPSIS

Object-oriented API

  use Carp::Object ();
  my $carper = Carp::Object->new(%options);

  # warn of error (from the perspective of caller)
  $carper->carp("this is very wrong") if some_bad_condition();

  # die of error (from the perspective of caller)
  $carper->croak("that's a dead end") if some_deadly_condition();
  
  # warn with full stacktrace
  $carper->cluck("this is very wrong");

  # die with full stacktrace
  $carper->confess("that's a dead end");

Functional API

  use Carp::Object qw/:all/;            # many other import options are available, see below
  our %CARP_OBJECT_CONSTRUCTOR = (...); # optional opportunity to tune the carping behaviour
  our @CARP_NOT = (...);                # optional opportunity to exclude packages from stack traces
  
  # warn of error (from the perspective of caller)
  carp "this is very wrong" if some_bad_condition();
  
  # die of error (from the perspective of caller)
  croak "that's a dead end" if some_deadly_condition();

  # full stacktrace
  cluck "this is very wrong";
  confess "that's a dead end";

  # temporary change some parameters, like for example the "clan" of modules to ignore
  { local %CARP_OBJECT_CONSTRUCTOR = (clan => qw(^(Foo|Bar)));
     croak "wrong call to Foo->.. or to Bar->.." if $something_is_wrong; }

DESCRIPTION

This is an object-oriented alternative to "croak" in Carp or "croak" in Carp::Clan, for reporting errors in modules from the perspective of the caller instead of reporting the internal implementation line where the error occurs.

Carp or Carp::Clan were designed long ago, at a time when Perl had no support yet for object-oriented programming; therefore they only have a functional API that is not very well suited for extensions. The present module attemps to mimic the same behaviour, but with an object-oriented implementation that offers more tuning options, and also supports errors raised as Exception objects.

Unlike Carp or Carp::Clan, where the presentation of stack frames is hard-coded, here it is delegated to Devel::StackTrace. This means that clients can also take advantage of options in Devel::StackTrace to tune the output -- or even replace it by another class.

Clients can choose between the object-oriented API, presented in the next chapter, or a traditional functional API compatible with Carp or Carp::Clan, presented in the following chapter.

DISCLAIMER: this module is very young and not battle-proofed yet. Despite many efforts to make it behave as close as possible to the original Carp, there might be some edge cases where it is not strictly equivalent. If you encounter such situations, please open an issue at https://github.com/damil/Carp-Object/issues.

METHODS

new

  use Carp::Object (); # '()' to avoid importing any symbols
  my $carper = Carp::Object->new(%options);

This is the constructor for a "carper" object. Options are :

verbose

if true, a 'croak' method call is treated as a 'confess', and a 'carp' is treated as a 'cluck'.

stacktrace_class

The class to be used for inspecting stack traces. Default is Devel::StackTrace.

clan

A regexp for identifying packages that should be skipped in stack traces, like in Carp::Clan. This option internally computes a frame_filter and therefore is incompatible with the frame_filter option.

display_frame

A reference to a subroutine for computing a textual representation of a stack frame. The default is _default_display_frame, which is a light wrapper on top of "as_string" in Devel::StackTrace::Frame, with improved representation of method calls. The given subroutine will receive three arguments :

1. a reference to a Devel::StackTrace::Frame instance

2. a boolean flag telling if this is the first stack frame in the list (because the display algorithm is usually different for the first stack frame).

3. A hashref of optional parameters. Currently there is only one option max_arg_length, discribed in "as_string(\%p)" in Devel::StackTrace.

display_frame_param

The optional hashref to be supplied as third parameter to the display_frame subroutine.

ignore_class

an arrayref of classes that will be passed to Devel::StackTrace; any class that belongs to or inherits from that list will be ignored in stack traces. Carp::Object will automatically add itself to the list supplied by the client.

In addition to these options, the constructor also accepts all options to "new" in Devel::StackTrace, like for example ignore_package, skip_frames, frame_filter, indent, etc.

croak

Die of error, from the perspective of the caller.

carp

Warn of error, from the perspective of the caller.

confess

Die of error, with full stack backtrace.

cluck

Warn of error, with full stack backtrace.

msg

  my $msg = $carper->msg($errstr, $n_frames);

Build the message to be used for dieing or warning. $errstr is the initial error message; it may be a plain string or an exception object with a stringification method. $n_frames is the number of stack frames to display (usually 1); if undefined, the whole stack trace is displayed.

FUNCTIONAL API: THE IMPORT() METHOD

  use Carp::Object;                # no import list => defaults to (':carp');
  # or
  use Carp::Object @import_list;

When using this functional API, subroutines equivalent to their corresponding object-oriented methods are exported into the caller's symbol table: the caller can then call carp, croak, etc. like with the venerable Carp module.

Import list

The import list accepts the following items :

carp, croak, confess and/or cluck

Individual import of specific routines

:carp

Import group equivalent to the list carp, croak, confess.

:all

Import group equivalent to the list carp, croak, confess, cluck.

\%options

A hashref within the import list is interpreted as a collection of importing options, in the spirit of Sub::Exporter or Exporter::Tiny. Admitted options are :

-as

  use Carp::Object carp => {-as => 'complain'}, croak => {-as => 'explode'};

Local name for the last imported function.

-prefix

  use Carp::Object qw/carp croak/, {-prefix => 'CO_'};
  ...
  CO_croak "aargh";

Names of imported functions will be prefixed by this string.

-suffix

  use Carp::Object qw/carp croak/, {-suffix => '_CO'};
  ...
  croak_CO "ouch";

Names of imported functions will be suffixed by this string.

-constructor_args

  use Carp::Object qw/carp croak/, {-constructor_args => {indent => 0}};

The given hashref will be passed to "new" in Carp::Object at each call to an imported function.

-reexport

  use Carp::Object -reexport => qw/carp croak/;

Imported symbols will be reexported into the caller of the caller ! This is useful when several modules from a same family share a common carping module. See DBIx::DataModel::Carp for an example (actually, this was the initial motivation for working on Carp::Object().

regexp

  use Carp::Object qw(^(MyClan::|FriendlyOther::));

If the import item "looks like a regexp", it is interpreted as syntactic sugar for use Carp::Object {-constructor_args => {clan => ..}}, in order to be compatible with the API of Carp::Clan.

The import item "looks like a regexp" if it starts with a '^' character, or contains a '|' or a '('.

Global variables

When using the functional API, customization of Carp::Object can be done indirectly through global variables in the calling package. Such variables can be localized in inner blocks if some specific behaviour is needed.

%CARP_OBJECT_CONSTRUCTOR

  { local %CARP_OBJECT_CONSTRUCTOR = (indent => 0);
    confess "I'm a great sinner"; # for this call, stack frames will not be indented
  }

The content of this hash will be passed to "new" in Carp::Object at each call to an imported function.

@CARP_NOT

The content of this array will be passed as ignore_package argument to to "new" in Carp::Object at each call to an imported function.

$Carp::Verbose

if true, a 'croak' method call is treated as a 'confess', and a 'carp' is treated as a 'cluck'.

INTERNAL SUBROUTINES

_default_display_frame

This is the internal routine for displaying a stack frame.

It calls "as_string" in Devel::StackTrace::Frame for doing most of the work. An additional feature is that the presentation string is rewritten for frames that "look like a method call" : instead of Foobar::method('Foobar=...', @other_args), we write Foobar=...->method(@other_args), so that method calls become apparent within the stack trace.

A frame "looks like a method call" if the first argument to the routine is a string identical to the class, or reference blessed into that class.

AUTHOR

Laurent Dami, <dami at cpan.org>

COPYRIGHT AND LICENSE

Copyright 2024 by Laurent Dami.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Carp::Object

perl -MCPAN -e shell
install Carp::Object