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.\"
.IX Title "HTML::Mason::Exceptions 3pm"
.TH HTML::Mason::Exceptions 3pm 2024-03-05 "perl v5.38.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
HTML::Mason::Exceptions \- Exception objects thrown by Mason
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  use HTML::Mason::Exceptions ( abbr => [ qw(system_error) ] );
\&
\&  open FH, \*(Aqfoo\*(Aq or system_error "cannot open foo: $!";
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module creates the hierarchy of exception objects used by Mason,
and provides some extra methods for them beyond those provided by
\&\f(CW\*(C`Exception::Class\*(C'\fR
.SH IMPORT
.IX Header "IMPORT"
When this module is imported, it is possible to specify a list of
abbreviated function names that you want to use to throw exceptions.
In the SYNOPSIS example, we use the \f(CW\*(C`system_error\*(C'\fR
function to throw a \f(CW\*(C`HTML::Mason::Exception::System\*(C'\fR exception.
.PP
These abbreviated functions do not allow you to set additional fields
in the exception, only the message.
.SH EXCEPTIONS
.IX Header "EXCEPTIONS"
.IP HTML::Mason::Exception 4
.IX Item "HTML::Mason::Exception"
This is the parent class for all exceptions thrown by Mason.  Mason
sometimes throws exceptions in this class when we could not find a
better category for the message.
.Sp
Abbreviated as \f(CW\*(C`error\*(C'\fR
.IP HTML::Mason::Exception::Abort 4
.IX Item "HTML::Mason::Exception::Abort"
The \f(CW\*(C`$m\->abort\*(C'\fR method was called.
.Sp
Exceptions in this class contain the field \f(CW\*(C`aborted_value\*(C'\fR.
.IP HTML::Mason::Exception::Decline 4
.IX Item "HTML::Mason::Exception::Decline"
The \f(CW\*(C`$m\->decline\*(C'\fR method was called.
.Sp
Exceptions in this class contain the field \f(CW\*(C`declined_value\*(C'\fR.
.IP HTML::Mason::Exception::Compilation 4
.IX Item "HTML::Mason::Exception::Compilation"
An exception occurred when attempting to \f(CW\*(C`eval\*(C'\fR an existing object
file.
.Sp
Exceptions in this class have the field \f(CW\*(C`filename\*(C'\fR, which indicates
what file contained the code that caused the error.
.Sp
Abbreviated as \f(CW\*(C`compilation_error\*(C'\fR.
.IP HTML::Mason::Exception::Compiler 4
.IX Item "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.
.Sp
Abbreviated as \f(CW\*(C`compiler_error\*(C'\fR.
.IP HTML::Mason::Exception::Compilation::IncompatibleCompiler 4
.IX Item "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.
.Sp
Abbreviated as \f(CW\*(C`wrong_compiler_error\*(C'\fR.
.IP HTML::Mason::Exception::Params 4
.IX Item "HTML::Mason::Exception::Params"
Invalid parameters were passed to a method or function.
.Sp
Abbreviated as \f(CW\*(C`param_error\*(C'\fR.
.IP HTML::Mason::Exception::Syntax 4
.IX Item "HTML::Mason::Exception::Syntax"
This exception indicates that a component contained invalid syntax.
.Sp
Exceptions in this class have the fields \f(CW\*(C`source_line\*(C'\fR, which is the
actual source where the error was found, \f(CW\*(C`comp_name\*(C'\fR, and
\&\f(CW\*(C`line_number\*(C'\fR.
.Sp
Abbreviated as \f(CW\*(C`syntax_error\*(C'\fR.
.IP HTML::Mason::Exception::System 4
.IX Item "HTML::Mason::Exception::System"
A system call of some sort, such as a file open, failed.
.Sp
Abbreviated as \f(CW\*(C`system_error\*(C'\fR.
.IP HTML::Mason::Exception::TopLevelNotFound 4
.IX Item "HTML::Mason::Exception::TopLevelNotFound"
The requested top level component could not be found.
.Sp
Abbreviated as \f(CW\*(C`top_level_not_found_error\*(C'\fR.
.IP HTML::Mason::VirtualMethod 4
.IX Item "HTML::Mason::VirtualMethod"
Some piece of code attempted to call a virtual method which was not
overridden.
.Sp
Abbreviated as \f(CW\*(C`virtual_error\*(C'\fR
.SH FIELDS
.IX Header "FIELDS"
Some of the exceptions mentioned above have additional fields, which
are available via accessors.  For example, to get the line number of
an \f(CW\*(C`HTML::Mason::Exception::Syntax\*(C'\fR exception, you call the
\&\f(CW\*(C`line_number\*(C'\fR method on the exception object.
.SH "EXCEPTION METHODS"
.IX Header "EXCEPTION METHODS"
All of the Mason exceptions implement the following methods:
.IP as_brief 4
.IX Item "as_brief"
This simply returns the exception message, without any trace information.
.IP as_line 4
.IX Item "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.
.IP as_text 4
.IX Item "as_text"
This returns the exception message and stack information, with each
frame on a separate line.
.IP as_html 4
.IX Item "as_html"
This returns the exception message and stack as an HTML page.
.PP
Each of these methods corresponds to a valid error_format parameter
for the Request object such as \f(CW\*(C`text\*(C'\fR or
\&\f(CW\*(C`html\*(C'\fR.
.PP
You can create your own method in the \f(CW\*(C`HTML::Mason::Exception\*(C'\fR
namespace, such as \f(CW\*(C`as_you_wish\*(C'\fR, 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.
.SH "EXCEPTION CLASS CHECKING"
.IX Header "EXCEPTION CLASS CHECKING"
This module also exports the \f(CW\*(C`isa_mason_exception\*(C'\fR function.  This
function takes the exception object and an optional string parameter
indicating what subclass to check for.
.PP
So it can be called either as:
.PP
.Vb 1
\&  if ( isa_mason_exception($@) ) { ... }
.Ve
.PP
or
.PP
.Vb 1
\&  if ( isa_mason_exception($@, \*(AqSyntax\*(Aq) ) { ... }
.Ve
.PP
Note that when specifying a subclass you should not include the
leading "HTML::Mason::Exception::" portion of the class name.