80eba3e5ff
The current documentation claims template files live in src, rather than resources - a fact trivially disprovable by either (a) referring to Leiningen's default templates in resources/leiningen/new or (b) actually trying to make a new template yourself. This commit updates the documentation to refer to the correct directory.
164 lines
6 KiB
Markdown
164 lines
6 KiB
Markdown
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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**Table of Contents** *generated with [DocToc](https://github.com/thlorenz/doctoc)*
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- [Writing Templates](#writing-templates)
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- [Structure](#structure)
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- [Templating System](#templating-system)
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- [A warning about Mustache tag delimiters](#a-warning-about-mustache-tag-delimiters)
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- [Distributing your Template](#distributing-your-template)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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# Writing Templates
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Suppose you've written a fabulously popular library, used the world
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over by adoring fans. For the purposes of this document, let's say
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this library is called "liquid-cool". If using liquid-cool takes a bit
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of setup, or if you'd just like to give your users a little guidance
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on how one might best create a new project which uses liquid-cool, you
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might want to provide a template for it (just like how `lein` already
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provides built-in templates for "app", "plugin", and so on).
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Let's assume your library's project dir is `~/dev/liquid-cool`. Create
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a template for it like so:
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cd ~/dev
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lein new template liquid-cool --to-dir liquid-cool-template
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Your new template would look like:
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liquid-cool-template
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├── LICENSE
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├── project.clj
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├── README.md
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├── resources
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| └── leiningen
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| └── new
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| └── liquid_cool
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| └── foo.clj
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└── src
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└── leiningen
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└── new
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└── liquid_cool.clj
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Note that you'll now have a new and separate project named
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"liquid-cool-template". It will have a group-id of "liquid-cool", and
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an artifact-id of "lein-template".
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> All lein templates have an artifact-id of "lein-template", and are
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> differentiated by their group-id, which always should match the
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> project for which they provide a template.
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## Structure
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The files that your template will provide to users are in
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`resources/leiningen/new/liquid_cool`. The template generator starts you off
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with just one, named "foo.clj". You can see it referenced in
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`src/leiningen/new/liquid_cool.clj`, right underneath the
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`->files data` line.
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You can delete `foo.clj` if you like (and its corresponding line in
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`liquid_cool.clj`), and start populating that
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`resources/leiningen/new/liquid_cool` directory with the files you wish to be
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part of your template. For everything you add, make sure the
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`liquid_cool.clj` file receives corresponding entries in that `->files`
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call. For examples to follow, have a look inside [the \*.clj files for
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the built-in
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templates](https://github.com/technomancy/leiningen/tree/stable/resources/leiningen/new).
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## Testing Your Template
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While developing a template, if you're in the template project directory,
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leiningen will pick it up and you'll be able to test it. e.g. from the
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`liquid-cool-template` dir:
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$ lein new liquid-cool myproject
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will create a directory called `myproject`, built from your template.
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Alternately, if you want to test your template from another directory on
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your system (without publishing your template to clojars yet), just run:
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$ lein install
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You should then be able to run `lein new liquid-cool myproject` from any
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directory on your system.
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## Templating System
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The default generated template uses [stencil][] for templating, which implements the
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language-agnostic templating system [Mustache][]. All the available tag types
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can be found in the [Mustache manual][mustache-manual]; we will only go through
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the most common tag type here.
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Suppose we want to add in a standard markdown readme file where the input name
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is the main header of the file. To be able to do so, we must do two things:
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Ensure that the input name is contained within the `data` mapped to the key X,
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and that we have a template file which looks up the key X by wrapping it in
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double mustaches like so: `{{X}}`. As for our input name, `data` already
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contains the line `:name name`, which means we can lookup the input name by
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writing `{{name}}` in the template file. To try it out, save the following
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contents in the file `resources/leiningen/new/liquid_cool/README.md`:
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```markdown
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# {{name}}
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This is our readme!
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```
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And add the following line right underneath the `->files data` line:
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```clj
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["README.md" (render "README.md" data)]
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```
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Now, if we for instance say `lein new liquid-cool liquid-cool-app`, the newly
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generated project will contain a file named `README.md` where the header is
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`liquid-cool-app`.
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[stencil]: https://github.com/davidsantiago/stencil
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[Mustache]: https://mustache.github.io/
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[mustache-manual]: https://mustache.github.io/mustache.5.html
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#### A warning about Mustache tag delimiters
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Clojure syntax can conflict with the default mustache tag delimiter. For
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example, when destructuring a nested map:
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```clj
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(let [{{:keys [a b]} :ab} some-map]
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(do-something a b))
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```
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Stencil will interpret the `{{` as the start of a mustache tag, but since the
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contents are not valid mustache, the render fails. To get around this, we can
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change the mustache delimiter temporarily, like so:
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```clj
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{{! Change mustache delimiter to <% and %> }}
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{{=<% %>=}}
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(let [{{:keys [a b]} :ab} some-map]
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(do-something a b))
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<%! Reset mustache delimiter %>
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<%={{ }}=%>
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```
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## Distributing your Template
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Templates are just maven artifacts. Particularly, they need only be on
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the classpath when `lein new` is called. So, as a side-effect, you
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can just put your templates in a jar and toss them on clojars and have
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people install them like normal Leiningen plugins.
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In Leiningen 2.x, templates get dynamically fetched if they're not
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found. So for instance `lein new heroku myproject` will find the
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latest version of the `heroku/lein-template` project from Clojars and
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use that.
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Users of Leiningen 1.x (1.6.2 or later) can also use the template if
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they install the `lein-newnew` plugin:
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$ lein plugin install lein-newnew 0.3.6
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$ lein new foo
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$ lein new plugin lein-foo
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