#============================================================= -*-Perl-*- # # Template::Context # # DESCRIPTION # Module defining a context in which a template document is processed. # This is the runtime processing interface through which templates # can access the functionality of the Template Toolkit. # # AUTHOR # Andy Wardley # # COPYRIGHT # Copyright (C) 1996-2000 Andy Wardley. All Rights Reserved. # Copyright (C) 1998-2000 Canon Research Centre Europe Ltd. # # This module is free software; you can redistribute it and/or # modify it under the same terms as Perl itself. # # REVISION # $Id: Context.pm,v 2.81 2003/07/24 11:32:35 abw Exp $ # #============================================================================ package Template::Context; require 5.004; use strict; use vars qw( $VERSION $DEBUG $AUTOLOAD $DEBUG_FORMAT ); use base qw( Template::Base ); use Template::Base; use Template::Config; use Template::Constants; use Template::Exception; $VERSION = sprintf("%d.%02d", q$Revision: 2.81 $ =~ /(\d+)\.(\d+)/); $DEBUG_FORMAT = "\n## \$file line \$line : [% \$text %] ##\n"; #======================================================================== # ----- PUBLIC METHODS ----- #======================================================================== #------------------------------------------------------------------------ # template($name) # # General purpose method to fetch a template and return it in compiled # form. In the usual case, the $name parameter will be a simple string # containing the name of a template (e.g. 'header'). It may also be # a reference to Template::Document object (or sub-class) or a Perl # sub-routine. These are considered to be compiled templates and are # returned intact. Finally, it may be a reference to any other kind # of valid input source accepted by Template::Provider (e.g. scalar # ref, glob, IO handle, etc). # # Templates may be cached at one of 3 different levels. The internal # BLOCKS member is a local cache which holds references to all # template blocks used or imported via PROCESS since the context's # reset() method was last called. This is checked first and if the # template is not found, the method then walks down the BLOCKSTACK # list. This contains references to the block definition tables in # any enclosing Template::Documents that we're visiting (e.g. we've # been called via an INCLUDE and we want to access a BLOCK defined in # the template that INCLUDE'd us). If nothing is defined, then we # iterate through the LOAD_TEMPLATES providers list as a 'chain of # responsibility' (see Design Patterns) asking each object to fetch() # the template if it can. # # Returns the compiled template. On error, undef is returned and # the internal ERROR value (read via error()) is set to contain an # error message of the form "$name: $error". #------------------------------------------------------------------------ sub template { my ($self, $name) = @_; my ($prefix, $blocks, $defblocks, $provider, $template, $error); my ($shortname, $blockname, $providers); $self->debug("template($name)") if $self->{ DEBUG }; # references to Template::Document (or sub-class) objects objects, or # CODE references are assumed to be pre-compiled templates and are # returned intact return $name if UNIVERSAL::isa($name, 'Template::Document') || ref($name) eq 'CODE'; $shortname = $name; unless (ref $name) { $self->debug("looking for block [$name]") if $self->{ DEBUG }; # we first look in the BLOCKS hash for a BLOCK that may have # been imported from a template (via PROCESS) return $template if ($template = $self->{ BLOCKS }->{ $name }); # then we iterate through the BLKSTACK list to see if any of the # Template::Documents we're visiting define this BLOCK foreach $blocks (@{ $self->{ BLKSTACK } }) { return $template if $blocks && ($template = $blocks->{ $name }); } # now it's time to ask the providers, so we look to see if any # prefix is specified to indicate the desired provider set. if ($^O eq 'MSWin32') { # let C:/foo through $prefix = $1 if $shortname =~ s/^(\w{2,})://o; } else { $prefix = $1 if $shortname =~ s/^(\w+)://; } if (defined $prefix) { $providers = $self->{ PREFIX_MAP }->{ $prefix } || return $self->throw(Template::Constants::ERROR_FILE, "no providers for template prefix '$prefix'"); } } $providers = $self->{ PREFIX_MAP }->{ default } || $self->{ LOAD_TEMPLATES } unless $providers; # Finally we try the regular template providers which will # handle references to files, text, etc., as well as templates # reference by name. If $blockname = ''; while ($shortname) { $self->debug("asking providers for [$shortname] [$blockname]") if $self->{ DEBUG }; foreach my $provider (@$providers) { ($template, $error) = $provider->fetch($shortname, $prefix); if ($error) { if ($error == Template::Constants::STATUS_ERROR) { # $template contains exception object if (UNIVERSAL::isa($template, 'Template::Exception') && $template->type() eq Template::Constants::ERROR_FILE) { $self->throw($template); } else { $self->throw( Template::Constants::ERROR_FILE, $template ); } } # DECLINE is ok, carry on } elsif (length $blockname) { return $template if $template = $template->blocks->{ $blockname }; } else { return $template; } } last if ref $shortname || ! $self->{ EXPOSE_BLOCKS }; $shortname =~ s{/([^/]+)$}{} || last; $blockname = length $blockname ? "$1/$blockname" : $1; } $self->throw(Template::Constants::ERROR_FILE, "$name: not found"); } #------------------------------------------------------------------------ # plugin($name, \@args) # # Calls on each of the LOAD_PLUGINS providers in turn to fetch() (i.e. load # and instantiate) a plugin of the specified name. Additional parameters # passed are propagated to the new() constructor for the plugin. # Returns a reference to a new plugin object or other reference. On # error, undef is returned and the appropriate error message is set for # subsequent retrieval via error(). #------------------------------------------------------------------------ sub plugin { my ($self, $name, $args) = @_; my ($provider, $plugin, $error); $self->debug("plugin($name, ", defined $args ? @$args : '[ ]', ')') if $self->{ DEBUG }; # request the named plugin from each of the LOAD_PLUGINS providers in turn foreach my $provider (@{ $self->{ LOAD_PLUGINS } }) { ($plugin, $error) = $provider->fetch($name, $args, $self); return $plugin unless $error; if ($error == Template::Constants::STATUS_ERROR) { $self->throw($plugin) if ref $plugin; $self->throw(Template::Constants::ERROR_PLUGIN, $plugin); } } $self->throw(Template::Constants::ERROR_PLUGIN, "$name: plugin not found"); } #------------------------------------------------------------------------ # filter($name, \@args, $alias) # # Similar to plugin() above, but querying the LOAD_FILTERS providers to # return filter instances. An alias may be provided which is used to # save the returned filter in a local cache. #------------------------------------------------------------------------ sub filter { my ($self, $name, $args, $alias) = @_; my ($provider, $filter, $error); $self->debug("filter($name, ", defined $args ? @$args : '[ ]', defined $alias ? $alias : '', ')') if $self->{ DEBUG }; # use any cached version of the filter if no params provided return $filter if ! $args && ! ref $name && ($filter = $self->{ FILTER_CACHE }->{ $name }); # request the named filter from each of the FILTERS providers in turn foreach my $provider (@{ $self->{ LOAD_FILTERS } }) { ($filter, $error) = $provider->fetch($name, $args, $self); last unless $error; if ($error == Template::Constants::STATUS_ERROR) { $self->throw($filter) if ref $filter; $self->throw(Template::Constants::ERROR_FILTER, $filter); } # return $self->error($filter) # if $error == &Template::Constants::STATUS_ERROR; } return $self->error("$name: filter not found") unless $filter; # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # commented out by abw on 19 Nov 2001 to fix problem with xmlstyle # plugin which may re-define a filter by calling define_filter() # multiple times. With the automatic aliasing/caching below, any # new filter definition isn't seen. Don't think this will cause # any problems as filters explicitly supplied with aliases will # still work as expected. # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # alias defaults to name if undefined # $alias = $name # unless defined($alias) or ref($name) or $args; # cache FILTER if alias is valid $self->{ FILTER_CACHE }->{ $alias } = $filter if $alias; return $filter; } #------------------------------------------------------------------------ # view(\%config) # # Create a new Template::View bound to this context. #------------------------------------------------------------------------ sub view { my $self = shift; require Template::View; return Template::View->new($self, @_) || $self->throw(&Template::Constants::ERROR_VIEW, $Template::View::ERROR); } #------------------------------------------------------------------------ # process($template, \%params) [% PROCESS template var=val ... %] # process($template, \%params, $local) [% INCLUDE template var=val ... %] # # Processes the template named or referenced by the first parameter. # The optional second parameter may reference a hash array of variable # definitions. These are set before the template is processed by # calling update() on the stash. Note that, unless the third parameter # is true, the context is not localised and these, and any other # variables set in the template will retain their new values after this # method returns. The third parameter is in place so that this method # can handle INCLUDE calls: the stash will be localized. # # Returns the output of processing the template. Errors are thrown # as Template::Exception objects via die(). #------------------------------------------------------------------------ sub process { my ($self, $template, $params, $localize) = @_; my ($trim, $blocks) = @$self{ qw( TRIM BLOCKS ) }; my (@compiled, $name, $compiled); my ($stash, $tblocks, $error, $tmpout); my $output = ''; $template = [ $template ] unless ref $template eq 'ARRAY'; $self->debug("process([ ", join(', '), @$template, ' ], ', defined $params ? $params : '', ', ', $localize ? '' : '', ')') if $self->{ DEBUG }; # fetch compiled template for each name specified foreach $name (@$template) { push(@compiled, $self->template($name)); } if ($localize) { # localise the variable stash with any parameters passed $stash = $self->{ STASH } = $self->{ STASH }->clone($params); } else { # update stash with any new parameters passed $self->{ STASH }->update($params); $stash = $self->{ STASH }; } eval { foreach $name (@$template) { $compiled = shift @compiled; my $element = ref $compiled eq 'CODE' ? { (name => (ref $name ? '' : $name), modtime => time()) } : $compiled; $stash->set('component', $element); unless ($localize) { # merge any local blocks defined in the Template::Document # into our local BLOCKS cache @$blocks{ keys %$tblocks } = values %$tblocks if UNIVERSAL::isa($compiled, 'Template::Document') && ($tblocks = $compiled->blocks()); } if (ref $compiled eq 'CODE') { $tmpout = &$compiled($self); } elsif (ref $compiled) { $tmpout = $compiled->process($self); } else { $self->throw('file', "invalid template reference: $compiled"); } if ($trim) { for ($tmpout) { s/^\s+//; s/\s+$//; } } $output .= $tmpout; } }; $error = $@; if ($localize) { # ensure stash is delocalised before dying $self->{ STASH } = $self->{ STASH }->declone(); } $self->throw(ref $error ? $error : (Template::Constants::ERROR_FILE, $error)) if $error; return $output; } #------------------------------------------------------------------------ # include($template, \%params) [% INCLUDE template var = val, ... %] # # Similar to process() above but processing the template in a local # context. Any variables passed by reference to a hash as the second # parameter will be set before the template is processed and then # revert to their original values before the method returns. Similarly, # any changes made to non-global variables within the template will # persist only until the template is processed. # # Returns the output of processing the template. Errors are thrown # as Template::Exception objects via die(). #------------------------------------------------------------------------ sub include { my ($self, $template, $params) = @_; return $self->process($template, $params, 'localize me!'); } #------------------------------------------------------------------------ # insert($file) # # Insert the contents of a file without parsing. #------------------------------------------------------------------------ sub insert { my ($self, $file) = @_; my ($prefix, $providers, $text, $error); my $output = ''; my $files = ref $file eq 'ARRAY' ? $file : [ $file ]; $self->debug("insert([ ", join(', '), @$files, " ])") if $self->{ DEBUG }; FILE: foreach $file (@$files) { my $name = $file; if ($^O eq 'MSWin32') { # let C:/foo through $prefix = $1 if $name =~ s/^(\w{2,})://o; } else { $prefix = $1 if $name =~ s/^(\w+)://; } if (defined $prefix) { $providers = $self->{ PREFIX_MAP }->{ $prefix } || return $self->throw(Template::Constants::ERROR_FILE, "no providers for file prefix '$prefix'"); } else { $providers = $self->{ PREFIX_MAP }->{ default } || $self->{ LOAD_TEMPLATES }; } foreach my $provider (@$providers) { ($text, $error) = $provider->load($name, $prefix); next FILE unless $error; if ($error == Template::Constants::STATUS_ERROR) { $self->throw($text) if ref $text; $self->throw(Template::Constants::ERROR_FILE, $text); } } $self->throw(Template::Constants::ERROR_FILE, "$file: not found"); } continue { $output .= $text; } return $output; } #------------------------------------------------------------------------ # throw($type, $info, \$output) [% THROW errtype "Error info" %] # # Throws a Template::Exception object by calling die(). This method # may be passed a reference to an existing Template::Exception object; # a single value containing an error message which is used to # instantiate a Template::Exception of type 'undef'; or a pair of # values representing the exception type and info from which a # Template::Exception object is instantiated. e.g. # # $context->throw($exception); # $context->throw("I'm sorry Dave, I can't do that"); # $context->throw('denied', "I'm sorry Dave, I can't do that"); # # An optional third parameter can be supplied in the last case which # is a reference to the current output buffer containing the results # of processing the template up to the point at which the exception # was thrown. The RETURN and STOP directives, for example, use this # to propagate output back to the user, but it can safely be ignored # in most cases. # # This method rides on a one-way ticket to die() oblivion. It does not # return in any real sense of the word, but should get caught by a # surrounding eval { } block (e.g. a BLOCK or TRY) and handled # accordingly, or returned to the caller as an uncaught exception. #------------------------------------------------------------------------ sub throw { my ($self, $error, $info, $output) = @_; local $" = ', '; # die! die! die! if (UNIVERSAL::isa($error, 'Template::Exception')) { die $error; } elsif (defined $info) { die (Template::Exception->new($error, $info, $output)); } else { $error ||= ''; die (Template::Exception->new('undef', $error, $output)); } # not reached } #------------------------------------------------------------------------ # catch($error, \$output) # # Called by various directives after catching an error thrown via die() # from within an eval { } block. The first parameter contains the errror # which may be a sanitized reference to a Template::Exception object # (such as that raised by the throw() method above, a plugin object, # and so on) or an error message thrown via die from somewhere in user # code. The latter are coerced into 'undef' Template::Exception objects. # Like throw() above, a reference to a scalar may be passed as an # additional parameter to represent the current output buffer # localised within the eval block. As exceptions are thrown upwards # and outwards from nested blocks, the catch() method reconstructs the # correct output buffer from these fragments, storing it in the # exception object for passing further onwards and upwards. # # Returns a reference to a Template::Exception object.. #------------------------------------------------------------------------ sub catch { my ($self, $error, $output) = @_; if (UNIVERSAL::isa($error, 'Template::Exception')) { $error->text($output) if $output; return $error; } else { return Template::Exception->new('undef', $error, $output); } } #------------------------------------------------------------------------ # localise(\%params) # delocalise() # # The localise() method creates a local copy of the current stash, # allowing the existing state of variables to be saved and later # restored via delocalise(). # # A reference to a hash array may be passed containing local variable # definitions which should be added to the cloned namespace. These # values persist until delocalisation. #------------------------------------------------------------------------ sub localise { my $self = shift; $self->{ STASH } = $self->{ STASH }->clone(@_); } sub delocalise { my $self = shift; $self->{ STASH } = $self->{ STASH }->declone(); } #------------------------------------------------------------------------ # visit($blocks) # # Each Template::Document calls the visit() method on the context # before processing itself. It passes a reference to the hash array # of named BLOCKs defined within the document, allowing them to be # added to the internal BLKSTACK list which is subsequently used by # template() to resolve templates. # from a provider. #------------------------------------------------------------------------ sub visit { my ($self, $blocks) = @_; unshift(@{ $self->{ BLKSTACK } }, $blocks) } #------------------------------------------------------------------------ # leave() # # The leave() method is called when the document has finished # processing itself. This removes the entry from the BLKSTACK list # that was added visit() above. For persistance of BLOCK definitions, # the process() method (i.e. the PROCESS directive) does some extra # magic to copy BLOCKs into a shared hash. #------------------------------------------------------------------------ sub leave { my $self = shift; shift(@{ $self->{ BLKSTACK } }); } #------------------------------------------------------------------------ # define_block($name, $block) # # Adds a new BLOCK definition to the local BLOCKS cache. $block may # be specified as a reference to a sub-routine or Template::Document # object or as text which is compiled into a template. Returns a true # value (the $block reference or compiled block reference) if # succesful or undef on failure. Call error() to retrieve the # relevent error message (i.e. compilation failure). #------------------------------------------------------------------------ sub define_block { my ($self, $name, $block) = @_; $block = $self->template(\$block) || return undef unless ref $block; $self->{ BLOCKS }->{ $name } = $block; } #------------------------------------------------------------------------ # define_filter($name, $filter, $is_dynamic) # # Adds a new FILTER definition to the local FILTER_CACHE. #------------------------------------------------------------------------ sub define_filter { my ($self, $name, $filter, $is_dynamic) = @_; my ($result, $error); $filter = [ $filter, 1 ] if $is_dynamic; foreach my $provider (@{ $self->{ LOAD_FILTERS } }) { ($result, $error) = $provider->store($name, $filter); return 1 unless $error; $self->throw(&Template::Constants::ERROR_FILTER, $result) if $error == &Template::Constants::STATUS_ERROR; } $self->throw(&Template::Constants::ERROR_FILTER, "FILTER providers declined to store filter $name"); } #------------------------------------------------------------------------ # reset() # # Reset the state of the internal BLOCKS hash to clear any BLOCK # definitions imported via the PROCESS directive. Any original # BLOCKS definitions passed to the constructor will be restored. #------------------------------------------------------------------------ sub reset { my ($self, $blocks) = @_; $self->{ BLKSTACK } = [ ]; $self->{ BLOCKS } = { %{ $self->{ INIT_BLOCKS } } }; } #------------------------------------------------------------------------ # stash() # # Simple accessor methods to return the STASH values. This is likely # to be called quite often so we provide a direct method rather than # relying on the slower AUTOLOAD. #------------------------------------------------------------------------ sub stash { return $_[0]->{ STASH }; } #------------------------------------------------------------------------ # define_vmethod($type, $name, \&sub) # # Passes $type, $name, and &sub on to stash->define_vmethod(). #------------------------------------------------------------------------ sub define_vmethod { my $self = shift; $self->stash->define_vmethod(@_); } #------------------------------------------------------------------------ # debugging($command, @args, \%params) # # Method for controlling the debugging status of the context. The first # argument can be 'on' or 'off' to enable/disable debugging, 'format' # to define the format of the debug message, or 'msg' to generate a # debugging message reporting the file, line, message text, etc., # according to the current debug format. #------------------------------------------------------------------------ sub debugging { my $self = shift; my $hash = ref $_[-1] eq 'HASH' ? pop : { }; my @args = @_; # print "*** debug(@args)\n"; if (@args) { if ($args[0] =~ /^on|1$/i) { $self->{ DEBUG_DIRS } = 1; shift(@args); } elsif ($args[0] =~ /^off|0$/i) { $self->{ DEBUG_DIRS } = 0; shift(@args); } } if (@args) { if ($args[0] =~ /^msg$/i) { return unless $self->{ DEBUG_DIRS }; my $format = $self->{ DEBUG_FORMAT }; $format = $DEBUG_FORMAT unless defined $format; $format =~ s/\$(\w+)/$hash->{ $1 }/ge; return $format; } elsif ($args[0] =~ /^format$/i) { $self->{ DEBUG_FORMAT } = $args[1]; } # else ignore } return ''; } #------------------------------------------------------------------------ # AUTOLOAD # # Provides pseudo-methods for read-only access to various internal # members. For example, templates(), plugins(), filters(), # eval_perl(), load_perl(), etc. These aren't called very often, or # may never be called at all. #------------------------------------------------------------------------ sub AUTOLOAD { my $self = shift; my $method = $AUTOLOAD; my $result; $method =~ s/.*:://; return if $method eq 'DESTROY'; warn "no such context method/member: $method\n" unless defined ($result = $self->{ uc $method }); return $result; } #------------------------------------------------------------------------ # DESTROY # # Stash may contain references back to the Context via macro closures, # etc. This breaks the circular references. #------------------------------------------------------------------------ sub DESTROY { my $self = shift; undef $self->{ STASH }; } #======================================================================== # -- PRIVATE METHODS -- #======================================================================== #------------------------------------------------------------------------ # _init(\%config) # # Initialisation method called by Template::Base::new() #------------------------------------------------------------------------ sub _init { my ($self, $config) = @_; my ($name, $item, $method, $block, $blocks); my @itemlut = ( LOAD_TEMPLATES => 'provider', LOAD_PLUGINS => 'plugins', LOAD_FILTERS => 'filters' ); # LOAD_TEMPLATE, LOAD_PLUGINS, LOAD_FILTERS - lists of providers while (($name, $method) = splice(@itemlut, 0, 2)) { $item = $config->{ $name } || Template::Config->$method($config) || return $self->error($Template::Config::ERROR); $self->{ $name } = ref $item eq 'ARRAY' ? $item : [ $item ]; } my $providers = $self->{ LOAD_TEMPLATES }; my $prefix_map = $self->{ PREFIX_MAP } = $config->{ PREFIX_MAP } || { }; while (my ($key, $val) = each %$prefix_map) { $prefix_map->{ $key } = [ ref $val ? $val : map { $providers->[$_] } split(/\D+/, $val) ] unless ref $val eq 'ARRAY'; # print(STDERR "prefix $key => $val => [", # join(', ', @{ $prefix_map->{ $key } }), "]\n"); } # STASH $self->{ STASH } = $config->{ STASH } || do { my $predefs = $config->{ VARIABLES } || $config->{ PRE_DEFINE } || { }; # hack to get stash to know about debug mode $predefs->{ _DEBUG } = ( ($config->{ DEBUG } || 0) & &Template::Constants::DEBUG_UNDEF ) ? 1 : 0 unless defined $predefs->{ _DEBUG }; Template::Config->stash($predefs) || return $self->error($Template::Config::ERROR); }; # compile any template BLOCKS specified as text $blocks = $config->{ BLOCKS } || { }; $self->{ INIT_BLOCKS } = $self->{ BLOCKS } = { map { $block = $blocks->{ $_ }; $block = $self->template(\$block) || return undef unless ref $block; ($_ => $block); } keys %$blocks }; # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # RECURSION - flag indicating is recursion into templates is supported # EVAL_PERL - flag indicating if PERL blocks should be processed # TRIM - flag to remove leading and trailing whitespace from output # BLKSTACK - list of hashes of BLOCKs defined in current template(s) # CONFIG - original configuration hash # EXPOSE_BLOCKS - make blocks visible as pseudo-files # DEBUG_FORMAT - format for generating template runtime debugging messages # DEBUG - format for generating template runtime debugging messages $self->{ RECURSION } = $config->{ RECURSION } || 0; $self->{ EVAL_PERL } = $config->{ EVAL_PERL } || 0; $self->{ TRIM } = $config->{ TRIM } || 0; $self->{ BLKSTACK } = [ ]; $self->{ CONFIG } = $config; $self->{ EXPOSE_BLOCKS } = defined $config->{ EXPOSE_BLOCKS } ? $config->{ EXPOSE_BLOCKS } : 0; $self->{ DEBUG_FORMAT } = $config->{ DEBUG_FORMAT }; $self->{ DEBUG_DIRS } = ($config->{ DEBUG } || 0) & Template::Constants::DEBUG_DIRS; $self->{ DEBUG } = defined $config->{ DEBUG } ? $config->{ DEBUG } & ( Template::Constants::DEBUG_CONTEXT | Template::Constants::DEBUG_FLAGS ) : $DEBUG; return $self; } #------------------------------------------------------------------------ # _dump() # # Debug method which returns a string representing the internal state # of the context object. #------------------------------------------------------------------------ sub _dump { my $self = shift; my $output = "[Template::Context] {\n"; my $format = " %-16s => %s\n"; my $key; foreach $key (qw( RECURSION EVAL_PERL TRIM )) { $output .= sprintf($format, $key, $self->{ $key }); } foreach my $pname (qw( LOAD_TEMPLATES LOAD_PLUGINS LOAD_FILTERS )) { my $provtext = "[\n"; foreach my $prov (@{ $self->{ $pname } }) { $provtext .= $prov->_dump(); # $provtext .= ",\n"; } $provtext =~ s/\n/\n /g; $provtext =~ s/\s+$//; $provtext .= ",\n ]"; $output .= sprintf($format, $pname, $provtext); } $output .= sprintf($format, STASH => $self->{ STASH }->_dump()); $output .= '}'; return $output; } 1; __END__ #------------------------------------------------------------------------ # IMPORTANT NOTE # This documentation is generated automatically from source # templates. Any changes you make here may be lost. # # The 'docsrc' documentation source bundle is available for download # from http://www.template-toolkit.org/docs.html and contains all # the source templates, XML files, scripts, etc., from which the # documentation for the Template Toolkit is built. #------------------------------------------------------------------------ =head1 NAME Template::Context - Runtime context in which templates are processed =head1 SYNOPSIS use Template::Context; # constructor $context = Template::Context->new(\%config) || die $Template::Context::ERROR; # fetch (load and compile) a template $template = $context->template($template_name); # fetch (load and instantiate) a plugin object $plugin = $context->plugin($name, \@args); # fetch (return or create) a filter subroutine $filter = $context->filter($name, \@args, $alias); # process/include a template, errors are thrown via die() $output = $context->process($template, \%vars); $output = $context->include($template, \%vars); # raise an exception via die() $context->throw($error_type, $error_message, \$output_buffer); # catch an exception, clean it up and fix output buffer $exception = $context->catch($exception, \$output_buffer); # save/restore the stash to effect variable localisation $new_stash = $context->localise(\%vars); $old_stash = $context->delocalise(); # add new BLOCK or FILTER definitions $context->define_block($name, $block); $context->define_filter($name, \&filtersub, $is_dynamic); # reset context, clearing any imported BLOCK definitions $context->reset(); # methods for accessing internal items $stash = $context->stash(); $tflag = $context->trim(); $epflag = $context->eval_perl(); $providers = $context->templates(); $providers = $context->plugins(); $providers = $context->filters(); ... =head1 DESCRIPTION The Template::Context module defines an object class for representing a runtime context in which templates are processed. It provides an interface to the fundamental operations of the Template Toolkit processing engine through which compiled templates (i.e. Perl code constructed from the template source) can process templates, load plugins and filters, raise exceptions and so on. A default Template::Context object is created by the Template module. Any Template::Context options may be passed to the Template new() constructor method and will be forwarded to the Template::Context constructor. use Template; my $template = Template->new({ TRIM => 1, EVAL_PERL => 1, BLOCKS => { header => 'This is the header', footer => 'This is the footer', }, }); Similarly, the Template::Context constructor will forward all configuration parameters onto other default objects (e.g. Template::Provider, Template::Plugins, Template::Filters, etc.) that it may need to instantiate. $context = Template::Context->new({ INCLUDE_PATH => '/home/abw/templates', # provider option TAG_STYLE => 'html', # parser option }); A Template::Context object (or subclass/derivative) can be explicitly instantiated and passed to the Template new() constructor method as the CONTEXT item. use Template; use Template::Context; my $context = Template::Context->new({ TRIM => 1 }); my $template = Template->new({ CONTEXT => $context }); The Template module uses the Template::Config context() factory method to create a default context object when required. The $Template::Config::CONTEXT package variable may be set to specify an alternate context module. This will be loaded automatically and its new() constructor method called by the context() factory method when a default context object is required. use Template; $Template::Config::CONTEXT = 'MyOrg::Template::Context'; my $template = Template->new({ EVAL_PERL => 1, EXTRA_MAGIC => 'red hot', # your extra config items ... }); =head1 METHODS =head2 new(\%params) The new() constructor method is called to instantiate a Template::Context object. Configuration parameters may be specified as a HASH reference or as a list of (name =E value) pairs. my $context = Template::Context->new({ INCLUDE_PATH => 'header', POST_PROCESS => 'footer', }); my $context = Template::Context->new( EVAL_PERL => 1 ); The new() method returns a Template::Context object (or sub-class) or undef on error. In the latter case, a relevant error message can be retrieved by the error() class method or directly from the $Template::Context::ERROR package variable. my $context = Template::Context->new(\%config) || die Template::Context->error(); my $context = Template::Context->new(\%config) || die $Template::Context::ERROR; The following configuration items may be specified. =over 4 =item VARIABLES, PRE_DEFINE The VARIABLES option (or PRE_DEFINE - they're equivalent) can be used to specify a hash array of template variables that should be used to pre-initialise the stash when it is created. These items are ignored if the STASH item is defined. my $context = Template::Context->new({ VARIABLES => { title => 'A Demo Page', author => 'Joe Random Hacker', version => 3.14, }, }; or my $context = Template::Context->new({ PRE_DEFINE => { title => 'A Demo Page', author => 'Joe Random Hacker', version => 3.14, }, }; =item BLOCKS The BLOCKS option can be used to pre-define a default set of template blocks. These should be specified as a reference to a hash array mapping template names to template text, subroutines or Template::Document objects. my $context = Template::Context->new({ BLOCKS => { header => 'The Header. [% title %]', footer => sub { return $some_output_text }, another => Template::Document->new({ ... }), }, }); =item TRIM The TRIM option can be set to have any leading and trailing whitespace automatically removed from the output of all template files and BLOCKs. By example, the following BLOCK definition [% BLOCK foo %] Line 1 of foo [% END %] will be processed is as "\nLine 1 of foo\n". When INCLUDEd, the surrounding newlines will also be introduced. before [% INCLUDE foo %] after output: before Line 1 of foo after With the TRIM option set to any true value, the leading and trailing newlines (which count as whitespace) will be removed from the output of the BLOCK. before Line 1 of foo after The TRIM option is disabled (0) by default. =item EVAL_PERL This flag is used to indicate if PERL and/or RAWPERL blocks should be evaluated. By default, it is disabled and any PERL or RAWPERL blocks encountered will raise exceptions of type 'perl' with the message 'EVAL_PERL not set'. Note however that any RAWPERL blocks should always contain valid Perl code, regardless of the EVAL_PERL flag. The parser will fail to compile templates that contain invalid Perl code in RAWPERL blocks and will throw a 'file' exception. When using compiled templates (see L and L), the EVAL_PERL has an affect when the template is compiled, and again when the templates is subsequently processed, possibly in a different context to the one that compiled it. If the EVAL_PERL is set when a template is compiled, then all PERL and RAWPERL blocks will be included in the compiled template. If the EVAL_PERL option isn't set, then Perl code will be generated which B throws a 'perl' exception with the message 'EVAL_PERL not set' B the compiled template code is run. Thus, you must have EVAL_PERL set if you want your compiled templates to include PERL and RAWPERL blocks. At some point in the future, using a different invocation of the Template Toolkit, you may come to process such a pre-compiled template. Assuming the EVAL_PERL option was set at the time the template was compiled, then the output of any RAWPERL blocks will be included in the compiled template and will get executed when the template is processed. This will happen regardless of the runtime EVAL_PERL status. Regular PERL blocks are a little more cautious, however. If the EVAL_PERL flag isn't set for the I context, that is, the one which is trying to process it, then it will throw the familiar 'perl' exception with the message, 'EVAL_PERL not set'. Thus you can compile templates to include PERL blocks, but optionally disable them when you process them later. Note however that it is possible for a PERL block to contain a Perl "BEGIN { # some code }" block which will always get run regardless of the runtime EVAL_PERL status. Thus, if you set EVAL_PERL when compiling templates, it is assumed that you trust the templates to Do The Right Thing. Otherwise you must accept the fact that there's no bulletproof way to prevent any included code from trampling around in the living room of the runtime environment, making a real nuisance of itself if it really wants to. If you don't like the idea of such uninvited guests causing a bother, then you can accept the default and keep EVAL_PERL disabled. =item RECURSION The template processor will raise a file exception if it detects direct or indirect recursion into a template. Setting this option to any true value will allow templates to include each other recursively. =item LOAD_TEMPLATES The LOAD_TEMPLATE option can be used to provide a reference to a list of Template::Provider objects or sub-classes thereof which will take responsibility for loading and compiling templates. my $context = Template::Context->new({ LOAD_TEMPLATES => [ MyOrg::Template::Provider->new({ ... }), Template::Provider->new({ ... }), ], }); When a PROCESS, INCLUDE or WRAPPER directive is encountered, the named template may refer to a locally defined BLOCK or a file relative to the INCLUDE_PATH (or an absolute or relative path if the appropriate ABSOLUTE or RELATIVE options are set). If a BLOCK definition can't be found (see the Template::Context template() method for a discussion of BLOCK locality) then each of the LOAD_TEMPLATES provider objects is queried in turn via the fetch() method to see if it can supply the required template. Each provider can return a compiled template, an error, or decline to service the request in which case the responsibility is passed to the next provider. If none of the providers can service the request then a 'not found' error is returned. The same basic provider mechanism is also used for the INSERT directive but it bypasses any BLOCK definitions and doesn't attempt is to parse or process the contents of the template file. This is an implementation of the 'Chain of Responsibility' design pattern as described in "Design Patterns", Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides), Addision-Wesley, ISBN 0-201-63361-2, page 223 . If LOAD_TEMPLATES is undefined, a single default provider will be instantiated using the current configuration parameters. For example, the Template::Provider INCLUDE_PATH option can be specified in the Template::Context configuration and will be correctly passed to the provider's constructor method. my $context = Template::Context->new({ INCLUDE_PATH => '/here:/there', }); =item LOAD_PLUGINS The LOAD_PLUGINS options can be used to specify a list of provider objects (i.e. they implement the fetch() method) which are responsible for loading and instantiating template plugin objects. The Template::Content plugin() method queries each provider in turn in a "Chain of Responsibility" as per the template() and filter() methods. my $context = Template::Context->new({ LOAD_PLUGINS => [ MyOrg::Template::Plugins->new({ ... }), Template::Plugins->new({ ... }), ], }); By default, a single Template::Plugins object is created using the current configuration hash. Configuration items destined for the Template::Plugins constructor may be added to the Template::Context constructor. my $context = Template::Context->new({ PLUGIN_BASE => 'MyOrg::Template::Plugins', LOAD_PERL => 1, }); =item LOAD_FILTERS The LOAD_FILTERS option can be used to specify a list of provider objects (i.e. they implement the fetch() method) which are responsible for returning and/or creating filter subroutines. The Template::Context filter() method queries each provider in turn in a "Chain of Responsibility" as per the template() and plugin() methods. my $context = Template::Context->new({ LOAD_FILTERS => [ MyTemplate::Filters->new(), Template::Filters->new(), ], }); By default, a single Template::Filters object is created for the LOAD_FILTERS list. =item STASH A reference to a Template::Stash object or sub-class which will take responsibility for managing template variables. my $stash = MyOrg::Template::Stash->new({ ... }); my $context = Template::Context->new({ STASH => $stash, }); If unspecified, a default stash object is created using the VARIABLES configuration item to initialise the stash variables. These may also be specified as the PRE_DEFINE option for backwards compatibility with version 1. my $context = Template::Context->new({ VARIABLES => { id => 'abw', name => 'Andy Wardley', }, }; =item DEBUG The DEBUG option can be used to enable various debugging features of the Template::Context module. use Template::Constants qw( :debug ); my $template = Template->new({ DEBUG => DEBUG_CONTEXT | DEBUG_DIRS, }); The DEBUG value can include any of the following. Multiple values should be combined using the logical OR operator, '|'. =over 4 =item DEBUG_CONTEXT Enables general debugging messages for the L module. =item DEBUG_DIRS This option causes the Template Toolkit to generate comments indicating the source file, line and original text of each directive in the template. These comments are embedded in the template output using the format defined in the DEBUG_FORMAT configuration item, or a simple default format if unspecified. For example, the following template fragment: Hello World would generate this output: ## input text line 1 : ## Hello ## input text line 2 : World ## World =back =back =head2 template($name) Returns a compiled template by querying each of the LOAD_TEMPLATES providers (instances of Template::Provider, or sub-class) in turn. $template = $context->template('header'); On error, a Template::Exception object of type 'file' is thrown via die(). This can be caught by enclosing the call to template() in an eval block and examining $@. eval { $template = $context->template('header'); }; if ($@) { print "failed to fetch template: $@\n"; } =head2 plugin($name, \@args) Instantiates a plugin object by querying each of the LOAD_PLUGINS providers. The default LOAD_PLUGINS provider is a Template::Plugins object which attempts to load plugin modules, according the various configuration items such as PLUGIN_BASE, LOAD_PERL, etc., and then instantiate an object via new(). A reference to a list of constructor arguments may be passed as the second parameter. These are forwarded to the plugin constructor. Returns a reference to a plugin (which is generally an object, but doesn't have to be). Errors are thrown as Template::Exception objects of type 'plugin'. $plugin = $context->plugin('DBI', 'dbi:msql:mydbname'); =head2 filter($name, \@args, $alias) Instantiates a filter subroutine by querying the LOAD_FILTERS providers. The default LOAD_FILTERS providers is a Template::Filters object. Additional arguments may be passed by list reference along with an optional alias under which the filter will be cached for subsequent use. The filter is cached under its own $name if $alias is undefined. Subsequent calls to filter($name) will return the cached entry, if defined. Specifying arguments bypasses the caching mechanism and always creates a new filter. Errors are thrown as Template::Exception objects of typre 'filter'. # static filter (no args) $filter = $context->filter('html'); # dynamic filter (args) aliased to 'padright' $filter = $context->filter('format', '%60s', 'padright'); # retrieve previous filter via 'padright' alias $filter = $context->filter('padright'); =head2 process($template, \%vars) Processes a template named or referenced by the first parameter and returns the output generated. An optional reference to a hash array may be passed as the second parameter, containing variable definitions which will be set before the template is processed. The template is processed in the current context, with no localisation of variables performed. Errors are thrown as Template::Exception objects via die(). $output = $context->process('header', { title => 'Hello World' }); =head2 include($template, \%vars) Similar to process() above, but using localised variables. Changes made to any variables will only persist until the include() method completes. $output = $context->include('header', { title => 'Hello World' }); =head2 throw($error_type, $error_message, \$output) Raises an exception in the form of a Template::Exception object by calling die(). This method may be passed a reference to an existing Template::Exception object; a single value containing an error message which is used to instantiate a Template::Exception of type 'undef'; or a pair of values representing the exception type and info from which a Template::Exception object is instantiated. e.g. $context->throw($exception); $context->throw("I'm sorry Dave, I can't do that"); $context->throw('denied', "I'm sorry Dave, I can't do that"); The optional third parameter may be a reference to the current output buffer. This is then stored in the exception object when created, allowing the catcher to examine and use the output up to the point at which the exception was raised. $output .= 'blah blah blah'; $output .= 'more rhubarb'; $context->throw('yack', 'Too much yacking', \$output); =head2 catch($exception, \$output) Catches an exception thrown, either as a reference to a Template::Exception object or some other value. In the latter case, the error string is promoted to a Template::Exception object of 'undef' type. This method also accepts a reference to the current output buffer which is passed to the Template::Exception constructor, or is appended to the output buffer stored in an existing Template::Exception object, if unique (i.e. not the same reference). By this process, the correct state of the output buffer can be reconstructed for simple or nested throws. =head2 define_block($name, $block) Adds a new block definition to the internal BLOCKS cache. The first argument should contain the name of the block and the second a reference to a Template::Document object or template sub-routine, or template text which is automatically compiled into a template sub-routine. Returns a true value (the sub-routine or Template::Document reference) on success or undef on failure. The relevant error message can be retrieved by calling the error() method. =head2 define_filter($name, \&filter, $is_dynamic) Adds a new filter definition by calling the store() method on each of the LOAD_FILTERS providers until accepted (in the usual case, this is accepted straight away by the one and only Template::Filters provider). The first argument should contain the name of the filter and the second a reference to a filter subroutine. The optional third argument can be set to any true value to indicate that the subroutine is a dynamic filter factory. Returns a true value or throws a 'filter' exception on error. =head2 localise(\%vars) Clones the stash to create a context with localised variables. Returns a reference to the newly cloned stash object which is also stored internally. $stash = $context->localise(); =head2 delocalise() Restore the stash to its state prior to localisation. $stash = $context->delocalise(); =head2 visit(\%blocks) This method is called by Template::Document objects immediately before they process their content. It is called to register any local BLOCK definitions with the context object so that they may be subsequently delivered on request. =head2 leave() Compliment to visit(), above. Called by Template::Document objects immediately after they process their content. =head2 reset() Clears the local BLOCKS cache of any BLOCK definitions. Any initial set of BLOCKS specified as a configuration item to the constructor will be reinstated. =head2 AUTOLOAD An AUTOLOAD method provides access to context configuration items. $stash = $context->stash(); $tflag = $context->trim(); $epflag = $context->eval_perl(); ... =head1 AUTHOR Andy Wardley Eabw@andywardley.comE L =head1 VERSION 2.81, distributed as part of the Template Toolkit version 2.10, released on 24 July 2003. =head1 COPYRIGHT Copyright (C) 1996-2003 Andy Wardley. All Rights Reserved. Copyright (C) 1998-2002 Canon Research Centre Europe Ltd. This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =head1 SEE ALSO L, L, L, L, L, L, L, L