NAME

Text::Xslate - Scalable template engine for Perl5

VERSION

This document describes Text::Xslate version v3.5.9.

SYNOPSIS

use Text::Xslate qw(mark_raw);

my $tx = Text::Xslate->new();

my %vars = (
    title => 'A list of books',
    books => [
        { title => 'Islands in the stream' },
        { title => 'Programming Perl'      },
        # ...
    ],

    # mark HTML components as raw not to escape its HTML tags
    gadget => mark_raw('<div class="gadget">...</div>'),
);

# for files
print $tx->render('hello.tx', \%vars);

# for strings (easy but slow)
my $template = q{
    <h1><: $title :></h1>
    <ul>
    : for $books -> $book {
        <li><: $book.title :></li>
    : } # for
    </ul>
};

print $tx->render_string($template, \%vars);

DESCRIPTION

Xslate is a template engine, tuned for persistent applications, safe as an HTML generator, and with rich features.

There are a lot of template engines in CPAN, for example Template-Toolkit, Text::MicroTemplate, HTML::Template, and so on, but all of them have some weak points: a full-featured template engine may be slow, while a fast template engine may be too simple to use. This is why Xslate is developed, which is the best template engine for web applications.

The concept of Xslate is strongly influenced by Text::MicroTemplate and Template-Toolkit 2, but the central philosophy of Xslate is different from them. That is, the philosophy is sandboxing that the template logic should not have no access outside the template beyond your permission.

Other remarkable features are as follows:

Features

High performance

This engine introduces the virtual machine paradigm. Templates are compiled into intermediate code, and then executed by the virtual machine, which is highly optimized for rendering templates. Thus, Xslate is much faster than any other template engines.

The template roundup project by Sam Graham shows Text::Xslate got amazingly high scores in instance_reuse condition (i.e. for persistent applications).

The template roundup project

http://illusori.co.uk/projects/Template-Roundup/
Perl Template Roundup October 2010 Performance vs Variant Report: instance_reuse

http://illusori.co.uk/projects/Template-Roundup/201010/performance_vs_variant_by_feature_for_instance_reuse.html

There are also benchmarks in benchmark/ directory in the Xslate distribution.

Smart escaping for HTML metacharacters

Xslate employs the smart escaping strategy, where a template engine escapes all the HTML metacharacters in template expressions unless users mark values as raw. That is, the output is unlikely to prone to XSS.

Template cascading

Xslate supports the template cascading, which allows you to extend templates with block modifiers. It is like a traditional template inclusion, but is more powerful.

This mechanism is also called as template inheritance.

Easiness to enhance

Xslate is ready to enhance. You can add functions and methods to the template engine and even add a new syntax via extending the parser.

INTERFACE

Methods

Text::Xslate->new(%options)

Creates a new Xslate template engine with options. You can reuse this instance for multiple calls to render().

Possible options are:

path => \@path // ['.']

Specifies the include paths, which may be directory names or virtual paths, i.e. HASH references which contain $file_name => $content pairs.

Note that if you use taint mode (-T), you have to give absolute paths to path and cache_dir. Otherwise you'll get errors because they depend on the current working directory which might not be secure.
cache => $level // 1

Sets the cache level.

If $level == 1 (default), Xslate caches compiled templates on the disk, and checks the freshness of the original templates every time.

If $level >= 2, caches will be created but the freshness will not be checked.

$level == 0 uses no caches, which is provided for testing.
cache_dir => $dir // "$ENV{HOME}/.xslate_cache"

Specifies the directory used for caches. If $ENV{HOME} doesn't exist, File::Spec->tmpdir will be used.

You should specify this option for productions to avoid conflicts of template names.
function => \%functions

Specifies a function map which contains name-coderef pairs. A function f may be called as f($arg) or $arg | f in templates.

Note that these registered functions have to return a text string, not a binary string unless you want to handle bytes in whole templates. Make sure what you want to use returns either a text string or a binary string.

For example, some methods of Time::Piece might return a binary string which is encoded in UTF-8, so you'll want to decode their values.
```
# under LANG=ja_JP.UTF-8 on MacOSX (Darwin 11.2.0)
use Time::Piece;
use Encode qw(decode);

sub ctime {
    my $ctime = Time::Piece->new->strftime; # UTF-8 encoded bytes
    return decode "UTF-8", $ctime;
}

my $tx = Text::Xslate->new(
    function => {
        ctime => \&ctime,
    },
    ...,
);
```
Built-in functions are described in Text::Xslate::Manual::Builtin.

module => [$module => ?\@import_args, ...]

Imports functions from $module, which may be a function-based or bridge module. Optional @import_args are passed to import as $module->import(@import_args).

For example:

# for function-based modules
my $tx = Text::Xslate->new(
    module => ['Digest::SHA1' => [qw(sha1_hex)]],
);
print $tx->render_string(
    '<: sha1_hex($x).substr(0, 6) :>',
    { x => foo() },
); # => 0beec7

# for bridge modules
my $tx = Text::Xslate->new(
    module => ['Text::Xslate::Bridge::Star'],
);
print $tx->render_string(
    '<: $x.uc() :>',
    { x => 'foo' },
); # => 'FOO'

Because you can use function-based modules with the module option, and also can invoke any object methods in templates, Xslate doesn't require specific namespaces for plugins.

html_builder_module => [$module => ?\@import_args, ...]

Imports functions from $module, wrapping each function with html_builder().
input_layer => $perliolayers // ':utf8'

Specifies PerlIO layers to open template files.
verbose => $level // 1

Specifies the verbose level.

If $level == 0, all the possible errors will be ignored.

If $level >= 1 (default), trivial errors (e.g. to print nil) will be ignored, but severe errors (e.g. for a method to throw the error) will be warned.

If $level >= 2, all the possible errors will be warned.
suffix => $ext // '.tx'

Specify the template suffix, which is used for cascade and include in Kolon.

Note that this is used for static name resolution. That is, the compiler uses it but the runtime engine doesn't.
syntax => $name // 'Kolon'

Specifies the template syntax you want to use.

$name may be a short name (e.g. Kolon), or a fully qualified name (e.g. Text::Xslate::Syntax::Kolon).

This option is passed to the compiler directly.
type => $type // 'html'

Specifies the output content type. If $type is html or xml, smart escaping is applied to template expressions. That is, they are interpolated via the html_escape filter. If $type is text smart escaping is not applied so that it is suitable for plain texts like e-mails.

$type may be html, xml (identical to html), and text.

This option is passed to the compiler directly.
line_start => $token // $parser_defined_str

Specify the token to start line code as a string, which quotemeta will be applied to. If you give undef, the line code style is disabled.

This option is passed to the parser via the compiler.
tag_start => $str // $parser_defined_str

Specify the token to start inline code as a string, which quotemeta will be applied to.

This option is passed to the parser via the compiler.
tag_end => $str // $parser_defined_str

Specify the token to end inline code as a string, which quotemeta will be applied to.

This option is passed to the parser via the compiler.
header => \@template_files

Specify the header template files, which are inserted to the head of each template.

This option is passed to the compiler.
footer => \@template_files

Specify the footer template files, which are inserted to the foot of each template.

This option is passed to the compiler.
warn_handler => \&cb

Specify the callback &cb which is called on warnings.
die_handler => \&cb

Specify the callback &cb which is called on fatal errors.
pre_process_handler => \&cb

Specify the callback &cb which is called after templates are loaded from the disk in order to pre-process template.

For example:
```
# Remove whitespace from templates
my $tx = Text::Xslate->new(
    pre_process_handler => sub {
        my $text = shift;
        $text=~s/\s+//g;
        return $text;
    }
);
```
The first argument is the template text string, which can be both text strings and byte strings.

This filter is applied only to files, not a string template for render_string.

$tx->render($file, \%vars) :Str

Renders a template file with given variables, and returns the result. \%vars is optional.

Note that $file may be cached according to the cache level.

$tx->render_string($string, \%vars) :Str

Renders a template string with given variables, and returns the result. \%vars is optional.

Note that $string is never cached, so this method should be avoided in production environment. If you want in-memory templates, consider the path option for HASH references which are cached as you expect:

my %vpath = (
    'hello.tx' => 'Hello, <: $lang :> world!',
);

my $tx = Text::Xslate->new( path => \%vpath );
print $tx->render('hello.tx', { lang => 'Xslate' });

Note that $string must be a text string, not a binary string.

$tx->load_file($file) :Void

Loads $file into memory for following render(). Compiles and saves it as disk caches if needed.

Text::Xslate->current_engine :XslateEngine

Returns the current Xslate engine while executing. Otherwise returns undef. This method is significant when it is called by template functions and methods.

Text::Xslate->current_vars :HashRef

Returns the current variable table, namely the second argument of render() while executing. Otherwise returns undef.

Text::Xslate->current_file :Str

Returns the current file name while executing. Otherwise returns undef. This method is significant when it is called by template functions and methods.

Text::Xslate->current_line :Int

Returns the current line number while executing. Otherwise returns undef. This method is significant when it is called by template functions and methods.

Text::Xslate->print(...) :Void

Adds the argument into the output buffer. This method is available on executing.

$tx->validate($file) :Void

Checks whether the syntax of $file is valid or invalid as Xslate. If it detects the invalid factor, this method throws the exception.

Exportable functions

`mark_raw($str :Str) :RawStr`

Marks $str as raw, so that the content of $str will be rendered as is, so you have to escape these strings by yourself.

For example:

use Text::Xslate qw( mark_raw );

my $tx   = Text::Xslate->new();
my $tmpl = 'Mailaddress: <: $email :>';
my %vars = (
    email => mark_raw('Foo &lt;foo at example.com&gt;'),
);
print $tx->render_string($tmpl, \%email);
# => Mailaddress: Foo &lt;foo@example.com&gt;

This function is available in templates as the mark_raw filter, although the use of it is strongly discouraged.

`unmark_raw($str :Str) :Str`

Clears the raw marker from $str, so that the content of $str will be escaped before rendered.

This function is available in templates as the unmark_raw filter.

`html_escape($str :Str) :RawStr`

Escapes HTML meta characters in $str, and returns it as a raw string (see above). If $str is already a raw string, it returns $str as is.

By default, this function will automatically be applied to all template expressions.

This function is available in templates as the html filter, but you're better off using unmark_raw to ensure that expressions are html-escaped.

`uri_escape($str :Str) :Str`

Escapes URI unsafe characters in $str, and returns it.

This function is available in templates as the uri filter.

`html_builder { block } | \&function :CodeRef`

Wraps a block or &function with mark_raw so that the new subroutine will return a raw string.

This function is used to tell the xslate engine that &function is an HTML builder that returns HTML sources. For example:

sub some_html_builder {
    my @args = @_;
    my $html;
    # build HTML ...
    return $html;
}

my $tx = Text::Xslate->new(
    function => {
        some_html_builder => html_builder(\&some_html_builder),
    },
);

Command line interface

The xslate(1) command is provided as a CLI to the Text::Xslate module, which is used to process directory trees or to evaluate one liners. For example:

$ xslate -Dname=value -o dest_path src_path

$ xslate -e 'Hello, <: $ARGV[0] :> wolrd!' Xslate
$ xslate -s TTerse -e 'Hello, [% ARGV.0 %] world!' TTerse

See xslate(1) for details.

TEMPLATE SYNTAX

There are multiple template syntaxes available in Xslate.

Kolon

Kolon is the default syntax, using <: ... :> inline code and : ... line code, which is explained in Text::Xslate::Syntax::Kolon.
Metakolon

Metakolon is the same as Kolon except for using [% ... %] inline code and %% ... line code, instead of <: ... :> and : ....
TTerse

TTerse is a syntax that is a subset of Template-Toolkit 2 (and partially TT3), which is explained in Text::Xslate::Syntax::TTerse.
HTMLTemplate

There's HTML::Template compatible layers in CPAN.

Text::Xslate::Syntax::HTMLTemplate is a syntax for HTML::Template.

HTML::Template::Parser is a converter from HTML::Template to Text::Xslate.

NOTES

There are common notes in Xslate.

Nil/undef handling

Note that nil (i.e. undef in Perl) handling is different from Perl's. Basically it does nothing, but verbose => 2 will produce warnings on it.

to print

Prints nothing.
to access fields

Returns nil. That is, nil.foo.bar.baz produces nil.
to invoke methods

Returns nil. That is, nil.foo().bar().baz() produces nil.
to iterate

Dealt as an empty array.
equality

$var == nil returns true if and only if $var is nil.

DEPENDENCIES

Perl 5.8.1 or later.

If you have a C compiler, the XS backend will be used. Otherwise the pure Perl backend will be used.

TODO

Context controls. e.g. <: [ $foo->bar @list ] :>.
Augment modifiers.
Default arguments and named arguments for macros.

External macros.

Just idea: in the new macro concept, macros and external templates will be the same in internals:

: macro foo($lang) { "Hello, " ~ $lang ~ " world!" }
: include foo { lang => 'Xslate' }
: # => 'Hello, Xslate world!'

: extern bar 'my/bar.tx';     # 'extern bar $file' is ok
: bar( value => 42 );         # calls an external template
: include bar { value => 42 } # ditto

A "too-safe" HTML escaping filter which escape all the symbolic characters

RESOURCES

PROJECT HOME: https://github.com/xslate/

REPOSITORY: https://github.com/xslate/p5-Text-Xslate/

BUGS

Please report issues at https://github.com/xslate/p5-Text-Xslate/issues. Patches are always welcome.

ACKNOWLEDGEMENT

Thanks to lestrrat for the suggestion to the interface of render(), the contribution of Text::Xslate::Runner (was App::Xslate), and a lot of suggestions.

Thanks to tokuhirom for the ideas, feature requests, encouragement, and bug finding.

Thanks to gardejo for the proposal to the name template cascading.

Thanks to makamaka for the contribution of Text::Xslate::PP.

Thanks to jjn1056 to the concept of template overlay (now implemented as cascade with ...).

Thanks to typester for the various inspirations.

Thanks to clouder for the patch of adding AND and OR to TTerse.

Thanks to punytan for the documentation improvement.

Thanks to chiba for the bug reports and patches.

Thanks to turugina for the patch to fix Win32 problems

Thanks to Sam Graham for the bug reports.

Thanks to Mons Anderson for the bug reports and patches.

Thanks to hirose31 for the feature requests and bug reports.

Thanks to c9s for the contribution of the documents.

Thanks to shiba_yu36 for the bug reports.

Thanks to kane46taka for the bug reports.

Thanks to cho45 for the bug reports.

Thanks to shmorimo for the bug reports.

Thanks to ueda for the suggestions.

AUTHOR

Fuji, Goro (gfx) gfuji@cpan.org.

Makamaka Hannyaharamitu (makamaka) (Text::Xslate::PP)

Maki, Daisuke (lestrrat) (Text::Xslate::Runner)

LICENSE AND COPYRIGHT

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

xslate / p5-Text-Xslate

readme