If you, as core developer, believe that "exceptions are the way to go", why does Moose produce such horrible, unhelpful, Java-style backtraces when dieing? For example when a type constraint is violated, I get about 7 lines of output that contribute nothing to the error cause, and have to combine the first and the last line to make up something that might actually relate to the error at hand:
Q:\>perl -MMoose -e "package Moo;use Moose; has 'foo' => (is => 'ro',
+isa => 'Int'); no Moose; package main; my $bar = Moo->new({foo => 'bo
+om'});"
Attribute (foo) does not pass the type constraint because: Validation
+failed for 'Int' failed with value boom at g:/Systeme/tools/pe
rl-5.10.0/perl/site/lib/Moose/Meta/Attribute.pm line 774
Moose::Meta::Attribute::_coerce_and_verify('Moose::Meta::Attri
+bute=HASH(0x190c5f4)', 'boom', 'Moo=HASH(0x190c934)') called a
t g:/Systeme/tools/perl-5.10.0/perl/site/lib/Moose/Meta/Attribute.pm l
+ine 428
Moose::Meta::Attribute::initialize_instance_slot('Moose::Meta:
+:Attribute=HASH(0x190c5f4)', 'Moose::Meta::Instance=HASH(0x187
145c)', 'Moo=HASH(0x190c934)', 'HASH(0x3ea354)') called at g:/Systeme/
+tools/perl-5.10.0/perl/site/lib/Class/MOP/Class.pm line 365
Class::MOP::Class::_construct_instance('Moose::Meta::Class=HAS
+H(0x187104c)', 'HASH(0x3ea354)') called at g:/Systeme/tools/pe
rl-5.10.0/perl/site/lib/Class/MOP/Class.pm line 352
Class::MOP::Class::new_object('Moose::Meta::Class=HASH(0x18710
+4c)', 'HASH(0x3ea354)') called at g:/Systeme/tools/perl-5.10.0
/perl/site/lib/Moose/Meta/Class.pm line 205
Moose::Meta::Class::new_object('Moose::Meta::Class=HASH(0x1871
+04c)', 'HASH(0x3ea354)') called at g:/Systeme/tools/perl-5.10.
0/perl/site/lib/Moose/Object.pm line 25
Moose::Object::new('Moo', 'HASH(0x12ca3ec)') called at -e line
+ 1
If you think something is a good engineering practice when using your tool, wouldn't it be a good idea to design your tool in a way that your tool encourages the practice instead of hindering it? Sending the programmer on a merry chase along exception paths is not friendly to the programmer.
If you use one of the standard exception mechanisms, like for example Carp, judicious use of @CARP_NOT can slim down the backtrace tree easily. Also, either passing down the (top-level) error cause to the place where the error gets detected will improve the feedback instead of requiring the programmer to intuit the error cause from the message(s) they get.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.