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ginger2: Jinja templates for Haskell

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Ginger2 approximates Jinja2 (https:/jinja.palletsprojects.com) in Haskell.

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Versions 2.0.0.0, 2.1.0.0, 2.1.0.1, 2.2.0.0, 2.3.0.0
Change log CHANGELOG
Dependencies aeson (>=2.2.3.0 && <2.3), array (>=0.5.4 && <0.6), base (>=4.14.0.0 && <5), base64-bytestring (>=1.2.1.0 && <1.3), bytestring (>=0.12.2.0 && <0.13), cmark (>=0.6.1 && <0.7), containers (>=0.7 && <0.9), directory (>=1.3.9 && <1.4), filepath (>=1.5.4.0 && <1.6), ginger2, megaparsec (>=9.7.0 && <9.8), MonadRandom (>=0.6.2 && <0.7), mtl (>=2.3.1 && <2.4), optparse-applicative (>=0.18.1.0 && <0.19), random (>=1.3.1 && <1.4), regex-tdfa (>=1.3.2.3 && <1.4), scientific (>=0.3.8 && <0.4), SHA (>=1.6.4.4 && <1.7), tasty (>=1.5.3 && <1.6), tasty-quickcheck (>=0.11.1 && <0.12), template-haskell (>=2.18.0.0 && <2.24), text (>=2.0 && <2.3), time (>=1.12 && <1.15), vector (>=0.13.2 && <0.14), yaml (>=0.10.0 && <0.12) [details]
License MIT
Copyright 2025 Tobias Dammers
Author Tobias Dammers
Maintainer tdammers@gmail.com
Category Language
Bug tracker https://github.com/tdammers/ginger2/issues
Source repo head: git clone https://github.com/tdammers/ginger2
Uploaded by TobiasDammers at 2025-06-13T20:51:30Z

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Ginger 2

A Haskell implementation of the Jinja template language.

Introduction

Ginger2 provides most of the Jinja template language, as much as that makes sense in a Haskell host application.

We do, however, avoid some of the most blatant Pythonisms, especially where we felt the features in question were more of an accidental result of binding template constructs to Python constructs.

We also add some optional features that are absent from the Python implementation, but that we felt useful and worth adding.

Installation

Ginger is available from Hackage, and can be installed using the usual methods.

Installing with Cabal:

cabal install ginger2

Using as part of another project:

Add the following to your .cabal's build-depends:

ginger2 ^>=2.0.0

Template Syntax

Template syntax largely follows Jinja2.

Important deviations are listed below.

Minimal example template

<!DOCTYPE html>
<html>
    <head>
        <title>{{ title }}</title>
    </head>
    {# This is a comment. Comments are removed from the output. #}
    <body>
        <menu id="nav-main">
        {% for item in navigation %}
            <li><a href="{{ item.url }}">{{ item.label }}</a></li>
        {% endfor %}
        </menu>
        <div class="layout-content-main">
            <h1>{{ title }}</h1>
            {{ body }}
        </div>
    </body>
</html>

For a full description of the syntax, refer to the Haddock documentation for the Language.Ginger module

Jinja syntax features absent from Ginger 2

Jinja functions, filters, and tests absent in Ginger 2

Functions/filters

Tests

Haskell API

The Haskell API is documented fully through Haddock documentation, available from Hackage. We'll just provide a short overview here.

Loading And Running A Template

The most straightforward way to run a template is to use the ginger function, which is parametrized over an underlying "carrier" Monad, m, and takes the following arguments:

Working With Ginger Values

The main data structure to represent Ginger values is Value; this type captures the "unitype" that Ginger uses internally.

The ToValue and FromValue typeclasses can be used to marshal Haskell values to and from Ginger, or you can work with Values directly.

Other types that appear in the surface API are Identifier (represents a variable or attribute name) and Scalar (represents a "scalar" type, i.e., none, booleans, numbers, strings, byte arrays, and encoded strings).

The GingerT Monad Transformer

The GingerT transformer captures an execution context/environment in which Ginger templates (and template fragments) can be evaluated/run. It adds the following concerns to the transformed base monad:

However, in some cases, it is necessary to implement functionality in terms of the raw base monad, representing failures as Either, and passing in context and, where necessary, execution state, as arguments. This is especially true when adding user-defined Haskell functions or native Haskell objects into the execution environment.