ersatz (historical revision 28483) - The CHICKEN Scheme wiki

You are looking at historical revision 28483 of this page. It may differ significantly from its current revision.

ersatz

A template engine compatible with Jinja2.

ersatz
Usage
Documentation
1. Procedures
2. Data types
Examples
About this egg

Documentation

The ersatz library provides a template engine somewhat compatible with the Jinja2 Python template engine. It is a based on a port of the Ocaml Jingoo library by Masaki WATANABE.

Procedures

Template environment and context initalization

[procedure] template-std-env :: [autoescape: BOOL] [search-path: STRING LIST] [filters: STRING LIST] [lexer-table: LEXER-TABLE] -> TEMPLATE-ENVIRONMENT

Creates a template evaluation environment to be used with init-context and the parsing and evaluation procedures in the next sections. The following optional arguments are recognized:

autoescape: BOOL: indicates whether to escape special HTML characters in expansion statements (#f by default)
search-path: STRING LIST: a list of directories to be searched for include files
filters: STRING LIST: a list of filters to be applied to the inpurt
lexer-table: LEXER-TABLE: a table generated by make-lexer-table

[procedure] init-context :: [env: TEMPLATE-ENVIRONMENT] [models: ALIST] [open-buffer: VOID -> PORT] -> TEMPLATE-CONTEXT

Initializes template context. The following optional arguments are recognized:

env: TEMPLATE-ENVIRONMENT: a structure created by template-std-env above
models: ALIST: an association list of the form (NAME . VALUE) where name is a symbol, and value is a template value, described below; names in the models list are to be substituted in expansion statements found in the input
open-buffer: VOID -> PORT: alternative procedure for creating the output port

Parsing

[procedure] statements-from-string :: TEMPLATE-ENVIRONMENT * STRING -> TSTMT LIST

Parses the given string and returns a list of template statements. See the section on data types for detailed definitions of the environment and statement types.

[procedure] statements-from-file :: TEMPLATE-ENVIRONMENT * STRING -> TSTMT LIST

Parses the given file and returns a list of template statements. See the section on data types for detailed definitions of the environment and statement types.

Evaluation

[procedure] from-string :: STRING [env: TEMPLATE-ENVIRONMENT] [models: ALIST] [ctx: TEMPLATE-CONTEXT] -> STRING

Parses the given string and evaluates the resulting template statements in the given context and models. See the section on data types for detailed definitions of the environment, context and statement types.

[procedure] from-file :: STRING [env: TEMPLATE-ENVIRONMENT] [models: ALIST] [ctx: TEMPLATE-CONTEXT] -> STRING

Parses the given file and evaluates the resulting template statements in the given context and models. See the section on data types for detailed definitions of the environment, context and statement types.

[procedure] eval-expr :: TEMPLATE-ENVIRONMENT * TEMPLATE-CONTEXT * TEXPR -> TVALUE
[procedure] eval-statement :: TEMPLATE-ENVIRONMENT * TEMPLATE-CONTEXT * TSTMT -> TEMPLATE-CONTEXT

Data types

(define-datatype tvalue tvalue? ...)

Representation of values in the template language. The value definitions are:

(Tnull): null value
(Tint (i integer?)): integers
(Tbool (b boolean?)): booleans
(Tfloat (n number?)): floating point numbers
(Tstr (s string?)): strings
(Tobj (x tvalue-alist?)): template objects; represented as alists where the key is a symbol and the value is a tvalue
(Tlist (x tvalue-list?)): lists
(Tset (x tvalue-list?)): sets
(Tfun (p procedure?)): template functions

Examples

`from-string`

 ;; expand and escape
 (from-string "{{danger}}" models: `((danger . ,(Tstr "<script>alert(1)</script>" ))))
  
 ==>

 "&lt;script&gt;alert(1)&lt;/script&gt;"


 ;; safe expand
 (from-string "{{danger|safe}}" models: `((danger . ,(Tstr "<script>alert(1)</script>" ))))
  
 ==>

 "<script>alert(1)</script>"

;; expand with filter
(from-string "{{pi|int}}" models: (list (cons 'pi (Tfloat 3.14))))

==>

"3"

;; if statement
(let* ( (source "{% if x <= 1 %}one{% elseif x == 2 %}two{% else %}three{% endif %}") )
  (from-string source  models: `((x . ,(Tint 3)))))
 
 ==>

 "three"

(print
  (let ( (source #<<EOF
{% for p in posts %}
 <div class="blog-post">
   <h3>{{ p.title }}</h3>
   <div class="post-body">
    {{ p.body }}
   </div>
 </div>
{% endfor %}
EOF
))
 (from-string source
   models:
     `((posts . ,(Tlist
                  (list (Tobj `((title . ,(Tstr "Post One title"))
                                (body  . ,(Tstr "Post One body"))
                         ))
                        (Tobj `((title . ,(Tstr "Post Two title"))
                                (body  . ,(Tstr "Post Two body"))
                         ))
                  ))
               )
           )) 
))

==>

 <div class="blog-post">
   <h3>Post One title</h3>
   <div class="post-body">
    Post One body
   </div>
 </div>

 <div class="blog-post">
   <h3>Post Two title</h3>
   <div class="post-body">
    Post Two body
   </div>
 </div>

`from-file`

 (from-file "cheatsheet.tmpl" env: (template-std-env search-path: '("dir/tmpl")))

Template cheat sheet


include test
============

{% include "header.tmpl" %}

binop
======

1+1 = {{ 1 + 1 }}
1-1 = {{ 1 - 1 }}
2*3 = {{ 2 * 3 }}
4/2 = {{ 4 / 2 }}
8^3 = {{ 8 ** 3 }}
8%3 = {{ 8 % 3 }}
not true = {{ !true }}
not true(2) = {{ not true }} 

single quote string test
=========================

{% set single_quoted = 'hoge' %}
single_quoted = {{single_quoted}}

expand test
===========

{% set danger = "<script>alert(1)</script>" %}
expand with escape = {{ danger }}
expand with safe = {{ danger|safe }}

set test
=========

set hoge = "ok"
{% set hoge = "ok" %}
now hoge = {{ hoge }}

if test
=======

{% if hoge == "ok" %}
value of hoge == "ok"
{% else %}
value of hoge != "ok"
{% endif %}

for test
========


{% for item in [1,2,3,4,5] %}
{% set tmp = "hoge" %}
<p>{{item}}</p>
<p>{{loop.cycle(1,2,3)}}</p>
<p>tmp = {{item}}</p>
{% endfor %}

{% for href, title in [ ("http://yahoo.co.jp", "yahoo japan") ] %}
<a href="{{href}}">{{title}}</a>
{% endfor %}

{% for href, title in [("http://yahoo.co.jp", "yahoo japan"), ("http://google.co.jp", "google japan")] %}
<a href="{{href}}">{{title}}</a>
{% endfor %}

{% for href, title in [("http://yahoo.co.jp", "yahoo japan"), ("http://google.co.jp", "google japan")] %}
<a href="{{href}}">{{title}}</a>
{% endfor %}

 obj test
=========

{% set obj = { age:10, name: 'aa' } %}

name = {{obj.name}}
age = {{obj.age}}
obj["name"] = {{ obj["name"] }}
obj["age"] = {{ obj["age"] }}

filter test
===========

upper test:{{ "must be upper"|upper }}
word count for "hoge hage hige" = {{ "hoge hage hige"|wordcount}}

func test
=========

range(0,3) = {% for x in range(0,3) %}{{x}}{% endfor %}
range(3,0) = {% for x in range(3,0) %}{{x}}{% endfor %}

strlen("testtest") = {{ strlen("testtest") }}
strlen("日本語") = {{ strlen("日本語") }}

round floor of 1.5 = {{1.5|round("floor")|int}}
round ceil of 1.5 = {{1.5|round("ceil")|int}}

join(",", [1,2,3,4,5]) = {{ join(",", [1,2,3,4,5]) }}

{% with long_list =  [10,20,30,40,50,60,70,80,90,100] %}
{% for row in slice(4, long_list) %}
  {% set y = loop.index %}
  {% for col in row %}
  {% set x = loop.index %}
  {{x}},{{y}} = {{col}}
  {% endfor %}
{% endfor %}
{% endwith %}


filter tag test
===============

{% filter upper %}
must be upper
{% endfilter %}

list expr
=========

{% for x in [1,2,3,4.5,"str"] %}{{x}}{% endfor %}
{% for x in [] %}{{x}}{% endfor %}

{{ join("-", [1,2,3]) }}

{{ "{{" }}

syntax test "is"
================

6 is divisibleby 4 = {{ 6 is divisibleby(4) }}
6 is divisibleby 3 = {{ 6 is divisibleby(3) }}
6 is divisibleby 2 = {{ 6 is divisibleby(2) }}
6 is divisibleby 2 = {{ 6 is divisibleby 2 }}
6 is divisibleby 3 via func = {{ divisibleby(3,6) }}

macro test
==========

{% macro hoge_macro(i,j) %}
{{i}},{{j}}
{% endmacro %}

{{ hoge_macro(10,20) }}

{# at this point, delay_macro is not declared, but we can call it. #}
{{ delay_macro(10,20) }}

{% macro delay_macro(x,y) %}
{{x}} {{ caller(1,2) }} {{y}}
{% endmacro %}

{% call(a,b) delay_macro("from", "to") %}
inner text!
args of call = {{a}},{{b}}
macro name = {{delay_macro.name}}
via caller = {{delay_macro.caller}}
{% endcall %}

1.3: Bug fixes in parsing of two-character operators
1.0: Initial release

License

Copyright 2012-2013 Ivan Raikov. 

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

A full copy of the GPL license can be found at
<http://www.gnu.org/licenses/>.