HTML::Mason::Exceptions - Exception objects thrown by Mason

  use HTML::Mason::Exceptions ( abbr => [ qw(system_error) ] );

  open FH, 'foo' or system_error "cannot open foo: $!";

This module creates the hierarchy of exception objects used by Mason, and provides some extra methods for them beyond those provided by CWException::Class

When this module is imported, it is possible to specify a list of abbreviated function names that you want to use to throw exceptions. In the SYNOPSIS example, we use the CWsystem_error function to throw a CWHTML::Mason::Exception::System exception.

These abbreviated functions do not allow you to set additional fields in the exception, only the message.

HTML::Mason::Exception

This is the parent class for all exceptions thrown by Mason. Mason sometimes throws exceptions in this class when we could not find a better category for the message. Abbreviated as CWerror

HTML::Mason::Exception::Abort

The CW$m->abort method was called. Exceptions in this class contain the field CWaborted_value.

HTML::Mason::Exception::Decline

The CW$m->decline method was called. Exceptions in this class contain the field CWdeclined_value.

HTML::Mason::Exception::Compilation

An exception occurred when attempting to CWeval an existing object file. Exceptions in this class have the field CWfilename, which indicates what file contained the code that caused the error. Abbreviated as CWcompilation_error.

HTML::Mason::Exception::Compiler

The compiler threw an exception because it received incorrect input. For example, this would be thrown if the lexer told the compiler to initialize compilation while it was in the middle of compiling another component. Abbreviated as CWcompiler_error.

HTML::Mason::Exception::Compilation::IncompatibleCompiler

A component was compiled by a compiler or lexer with incompatible options. This is used to tell Mason to recompile a component. Abbreviated as CWwrong_compiler_error.

HTML::Mason::Exception::Params

Invalid parameters were passed to a method or function. Abbreviated as CWparam_error.

HTML::Mason::Exception::Syntax

This exception indicates that a component contained invalid syntax. Exceptions in this class have the fields CWsource_line, which is the actual source where the error was found, CWcomp_name, and CWline_number. Abbreviated as CWsyntax_error.

HTML::Mason::Exception::System

A system call of some sort, such as a file open, failed. Abbreviated as CWsystem_error.

HTML::Mason::Exception::TopLevelNotFound

The requested top level component could not be found. Abbreviated as CWtop_level_not_found_error.

HTML::Mason::VirtualMethod

Some piece of code attempted to call a virtual method which was not overridden. Abbreviated as CWvirtual_error

Some of the exceptions mentioned above have additional fields, which are available via accessors. For example, to get the line number of an CWHTML::Mason::Exception::Syntax exception, you call the CWline_number method on the exception object.

All of the Mason exceptions implement the following methods:

as_brief

This simply returns the exception message, without any trace information.

as_line

This returns the exception message and its trace information, all on a single line with tabs between the message and each frame of the stack trace.

as_text

This returns the exception message and stack information, with each frame on a separate line.

as_html

This returns the exception message and stack as an HTML page.

Each of these methods corresponds to a valid error_format parameter for the Request object such as CWtext or CWhtml.

You can create your own method in the CWHTML::Mason::Exception namespace, such as CWas_you_wish, in which case you could set this parameter to you_wish. This method will receive a single argument, the exception object, and is expected to return some sort of string containing the formatted error message.

This module also exports the CWisa_mason_exception function. This function takes the exception object and an optional string parameter indicating what subclass to check for.

So it can be called either as:

  if ( isa_mason_exception($@) ) { ... }

or

  if ( isa_mason_exception($@, 'Syntax') ) { ... }

Note that when specifying a subclass you should not include the leading HTML::Mason::Exception:: portion of the class name.