Awesome
jekyll_plugin_support
![Gem Version](https://badge.fury.io/rb/jekyll_plugin_support.svg)
Jekyll_plugin_support
is a Ruby gem that provides a framework for writing and testing Jekyll plugins.
Jekyll_plugin_support
can be used to create simple Jekyll plugins in
the _plugins/
directory of your Jekyll project, or gem-based Jekyll plugins.
At present, only Jekyll tags and blocks are supported.
Plugins that use jekyll_plugin_support
include:
... and also the demonstration plugins in
jekyll_plugin_support
Features
Jekyll plugin tags created from jekyll_plugin_support
framework automatically have the following features:
- Boilerplate is removed, so you can focus on the required logic and output.
- Arguments are parsed for keywords and name/value parameters.
- Single or double quotes can be used for arguments and parameters.
- Important variables are defined.
- Error handling is standardized, and includes an automatically defined error type and corresponding CSS tag for each Jekyll tag.
- Liquid variables can be passed as parameters to tags, and used in the body of block tags.
- Registration is automatic, and important configuration details are reported during registration.
- A custom logger is created for each tag, independent of the default Jekyll logger.
- Variables can be defined in
_config.yml
, and optionally have different values for debug mode, production mode and test mode. - An attribution message is available.
- Draft pages are automatically detected.
In addition, a demonstration website is provided for easy testing of your plugins.
Installation
Jekyll_plugin_support
is packaged as a Ruby gem.
If your project is a custom plugin that will reside in a Jekyll project’s _plugins
directory,
add the following line to your Jekyll plugin’s Gemfile
.
group :jekyll_plugins do
# ...
gem 'jekyll_plugin_support', '>= 0.8.0'
# ...
end
Otherwise, if your custom plugin will be packaged into a gem, add the following to your plugin’s .gemspec
:
Gem::Specification.new do |spec|
# ...
spec.add_dependency 'jekyll_plugin_support', '>= 0.8.0'
# ...
end
Install the jekyll_plugin_support
Ruby gem and mark it as a dependency of your project by typing:
$ bundle
Copy the CSS classes from demo/assets/css/jekyll_plugin_support.css
to your Jekyll project’s CSS file.
About jekyll_plugin_support
JekyllSupport::JekyllBlock
and JekyllSupport::JekyllTag
provide support for Jekyll tag block plugins
and Jekyll inline tag plugins, respectively.
They are very similar in construction and usage.
Instead of subclassing your custom Jekyll block tag class from Liquid::Block
,
subclass from JekyllSupport::JekyllBlock
.
Similarly, instead of subclassing your custom Jekyll tag class from Liquid::Tag
,
subclass from JekyllSupport::JekyllTag
.
Both JekyllSupport classes instantiate new instances of
PluginMetaLogger
(called @logger
) and
JekyllPluginHelper
(called @helper
).
JekyllPluginHelper
defines a generic initialize method, and your tag or block tag class should not need to override it.
Also, your tag or block tag class should not define a method called render, because jekyll_plugin_support
defines one.
Instead, define a method called render_impl
.
For inline tags, render_impl
does not accept any parameters.
For block tags, a single parameter is required, which contains text passed from your block in the page.
Your implementation of render_impl can parse parameters passed to the tag / block tag, as described in Tag Parameter Parsing.
General Usage
Please see the demo/
project for a well-documented set of demonstration Jekyll plugins that are built from jekyll_plugin_support
.
Additional information is available here and the
jekyll_plugin_support
documentation.
JekyllSupport::JekyllBlock
and
JekyllSupport::JekyllTag
provide
support for Jekyll block tags and Jekyll inline tags, respectively.
They are similar in construction and usage.
Instead of subclassing your Jekyll block tag class from Liquid::Block
,
subclass from JekyllSupport::JekyllBlock
instead.
Likewise, instead of subclassing your Jekyll inline tag class from Liquid::Tag
,
subclass from JekyllSupport::JekyllTag
instead.
Both JekyllSupport
classes instantiate new instances of
PluginMetaLogger
(called @logger
) and
JekyllPluginHelper
(called @helper
).
Inline and Block Tag Plugin Implementation
Both JekyllSupport
classes define a generic initialize
method,
and your inline tag or block tag class should not override it.
Also, your inline tag or block tag class should not define a method called render
,
because both JekyllSupport
classes define this method.
Instead, define a method called render_impl
.
For inline tags, render_impl
does not accept any parameters.
For block tags, a single parameter is required, which contains any text enclosed within your block.
Predefined Plugin Variables
Jekyll_plugin_support
defines the following Ruby variables that you can use in your plugin’s render_impl
method:
-
@argument_string
Unparsed markup passed as a parameter to your block tag and inline tag. -
@attribution
Attribution markup -
@helper
JekyllPluginHelper
instance for your plugin. -
@layout
Layout information -
@logger
jekyll_plugin_logger
instance for your Jekyll plugin. -
@mode
Indicatesproduction
,test
ordevelopment
mode. -
@page
Page variables -
@paginator
Pagination variables -
@site
Site variables -
@tag_config
Contents of the section of_config.yml
named after your plugin. -
@tag_name
Name of your Jekyll block tag or inline tag plugin. -
@theme
Theme variables -
text
Content provided to your block tag.
Argument Parsing
Tag arguments can be obtained within render_impl
.
Both keyword options and name/value parameters are supported.
Both JekyllTag
and JekyllBlock
use the standard Ruby mechanism for parsing command-line options:
shellwords
and
key_value_parser
.
All your code has to do is to specify the keywords to search for in the string
passed from the HTML page that your tag is embedded in.
The included demo
website has examples;
both demo/_plugins/demo_inline_tag.rb
and
demo/_plugins/demo_block_tag.rb
contain the following:
@keyword1 = @helper.parameter_specified? 'keyword1'
@keyword2 = @helper.parameter_specified? 'keyword2'
@name1 = @helper.parameter_specified? 'name1'
@name2 = @helper.parameter_specified? 'name2'
If an argument has a variable reference in it, the value of the variable is substituted for the reference. For example, given:
_layouts/default.html
defines a variable calledvar_layout
in its front matter.index.html
defines a variable calledvar_page
in its front matter.index.html
assigns a variable calledx
via the liquidassign
statement.
... then the following references in a page will be substituted for their values in arguments and in block tag bodies:
{% my_block_tag
param1="x={{x}}"
param2="var_page={{page.var_page}}"
param3="var_layout={{layout.var_layout}}"
%}
Assigned variables do not need a namespace: x={{x}}
Page variables must be qualified with the 'page' namespace:
var_page={{page.var_page}}
Layout variables must be qualified with the 'layout' namespace:
var_layout={{layout.var_layout}}
{% endmy_block_tag %}
You can see similar code in demo/demo_inline_tag.html
.
The page['excerpt']
and page['output']
key/value pairs are removed from processing because of recursion issues.
You cannot look up those values from a jekyll_plugin_support
plugin.
Keyword Options
For all keyword options, values specified in the document may be provided.
If a value is not provided, the value true
is assumed.
Otherwise, if a value is provided, it must be wrapped in single or double quotes.
Examples
The following examples use the die_if_error
keyword option for the
pre
and
exec
tags from the jekyll_pre
plugin %}.
Specifying Tag Option Values
The following sets die_if_error
true
:
{% pre die_if_error %} ... {% endpre %}
The above is the same as writing:
{% pre die_if_error='true' %} ... {% endpre %}
Or writing:
{% pre die_if_error="true" %} ... {% endpre %}
Neglecting to provide surrounding quotes around the provided value causes the parser to not recognize the option.
Instead, what you had intended to be the keyword/value pair will be parsed as part of the command.
For the pre
tag, this means the erroneous string becomes part of the label
value,
unless label
is explicitly specified.
For the exec
tag, this means the erroneous string becomes part of the command to execute.
The following demonstrates the error.
{% pre die_if_error=false %} ... {% endpre %}
The above causes the label to be die_if_error=false
.
{% exec die_if_error=false ls %} ... {% endpre %}
The above causes the command to be executed to be die_if_error=false ls
instead of ls
.
Quoting
Parameter values can be quoted.
If the value consists of only one token then quoting is optional. The following name/value parameters all have the same result:
pay_tuesday="true"
pay_tuesday='true'
pay_tuesday=true
pay_tuesday
If the values consist of more than one token, quotes must be used. The following examples both yield the same result:
pay_tuesday="maybe not"
pay_tuesday='maybe not'
Remaining Markup
After your plugin has parsed all the keyword options and name/value parameters,
call @helper.remaining_markup
to obtain the remaining markup that was passed to your plugin.
Configuration Variables
jekyll_plugin_support
provides support for
Liquid variables
to be defined in _config.yml
, in a section called liquid-vars
.
These variables behave exactly like Liquid variables defined by assign
and capture
expressions,
except they are global in scope; these variables are available in every Jekyll web page.
The following _config.yml
fragment defines 3 variables called var1
, var2
and var3
:
liquid-vars:
var1: value1
var2: 'value 2'
var3: value3
Liquid variables defined in this manner are intended to be embedded in a webpage. They are can be used like any other Liquid variable.
Variable Expansion
Jekyll expands Liquid variable references during the page rendering process.
Jekyll does not expand Liquid variable references passes as parameters to tag and block plugins, however.
However, plugins made from jekyll_plugin_support
automatically
expand all types of variable references passed as parameters and in block tag bodies.
Jekyll_plugin_support
tag and block plugins expand the following types of variables:
- Jekyll_plugin_support configuration variables, discussed above.
- Jekyll page and layout variables.
- Inline Liquid variables (defined in assign and capture statements).
In the following example web page, Jekyll expands the var1
reference within the <p></p>
tag,
but not the var1
or var2
references passed to my_plugin
.
<p>This is the value of var1: {{var1}}.</p>
{% my_plugin param1="{{var1}}" param2="{{var2}}" %}
Assuming that my_plugin
was written as a jekyll_plugin_support
plugin,
all variable references in its parameters are expanded.
Thus, the above is interpreted as follows when my_plugin
is evaluated during the Jekyll rendering process:
<p>This is the value of var1: value1.</p>
{% my_plugin param1="value1" param2="value 2" %}
Jekyll_plugin_support
expands most of the plugin variables described above,
replacing Liquid variable references with their values.
The exception is @argument_string
, which is not expanded.
Liquid Variable Values Specific To Production And Development Modes
jekyll_plugin_support
allows Liquid variables defined in _config.yml
to have different values
when Jekyll is running in development
, production
and test
modes.
When injecting variables into your Jekyll website, Jekyll_plugin_support
refers to definitions specific to the current environment,
and then refers to other definitions that are not overridden.
Here is an example:
liquid-vars:
development:
var1: 'http://localhost:4444/demo_block_tag.html'
var2: 'http://localhost:4444/demo_inline_tag.html'
production:
var1: 'https://github.com/django/django/blob/3.1.7'
var2: 'https://github.com/django-oscar/django-oscar/blob/3.0.2'
var3: 'https://github.com/mslinn'
For the above, the following variable values are set in development
mode:
var1
:http://localhost:4444/demo_block_tag.html
var2
:http://localhost:4444/demo_inline_tag.html
var3
:https://github.com/mslinn
... and the following variable values are set in production
and test
modes:
var1
:https://github.com/django/django/blob/3.1.7
var2
:https://github.com/django-oscar/django-oscar/blob/3.0.2
var3
:https://github.com/mslinn
Liquid Variables in jekyll_plugin_support
Subclasses
You can define additional Liquid variables in plugins built using jekyll_plugin_support
.
To do this, make entries in _config.yml
under a key named after the value of @tag_name
.
For example, let’s imagine you create a plugin using jekyll_plugin_support
,
and hou register it with the name phonetic_alphabet
.
You could define Liquid variables that would be made available to content pages in web applications that
incorporate the phonetic_alphabet
plugin.
The following section in _config.yml
defines variables called x
, y
and z
,
with values xray
, yankee
and zulu
, respectively:
phonetic_alphabet:
x: xray
y: yankee
z: zulu
The above definitions allow you to write content pages that use those variables, like the following page containing markup:
---
layout: default
title: Variable demo
---
The letter `x` is pronounced {{x}}.
Similarly, the letters `y` and `z` are pronounced {{y}} and {{z}}.
Automatically Created Error Classes
JekyllSupport::JekyllBlock
and JekyllSupport::JekyllTag
subclasses
automatically create error classes, named after the subclass.
For example, if you create a JekyllSupport::JekyllBlock
subclass called DemoBlockTag
,
the automatically generated error class will be called DemoBlockTagError
.
Although you could use it as you would any other error class, JekyllPluginSupport
provides some helper methods.
These methods fill in the page path and line number that caused the error, shorten the stack trace,
log an error message, and can be used to return an HTML-friendly version of the message to the web page.
The following example is a shortened version of demo/_plugins/demo_block_tag.rb
.
You might want to write similar code in your rescue
blocks.
class DemoBlock < JekyllSupport::JekyllBlock
VERSION = '0.1.2'.freeze
def render_impl(text)
raise DemoBlockTagError, 'Fall down, go boom.'
rescue DemoBlockTagError => e
@logger.error e.logger_message
exit! 1 if @die_on_demo_block_error
e.html_message
end
end
Error class methods have been provided for standardized and convenient error handling:
shorten_backtrace
- most of the lines that spew from a Jekyll backtrace are uninteresting.logger_message
- The message is constructed from the string provided when the error was raised, with the page path and line number added.html_message
- The same aslogger_message
, but constructed with HTML.
Self-Reporting Upon Registration
When each tag is registered, it self-reports, for example:
INFO PluginMetaLogger: Loaded plugin demo_inline_tag v0.1.2. It has:
Error class: DemoTagError
CSS class for error messages: demo_tag_error
_config.yml contains the following configuration for this plugin:
{"die_on_demo_tag_error"=>false, "die_on_standard_error"=>false}
INFO PluginMetaLogger: Loaded plugin demo_inline_tag_no_arg v0.1.0. It has:
Error class: DemoTagNoArgsError
CSS class for error messages: demo_tag_no_args_error
_config.yml does not contain configuration information for this plugin.
You could add a section containing default values by specifying a section for the tag name,
and an entry whose name starts with `die_on_`, followed by a snake_case version of the error name.
demo_inline_tag_no_arg:
die_on_demo_tag_no_args_error: false
no_arg_parsing
Optimization
If your tag or block plugin only needs access to the raw arguments passed from the web page,
without tokenization, and you expect that the plugin might be invoked with large amounts of text,
derive your plugin from JekyllBlockNoArgParsing
or JekyllTagNoArgParsing
.
Attribution
JekyllTag
and JekyllBlock
subclasses of jekyll_plugin_support
can utilize the attribution
option if they are published as a gem.
JekyllTagNoArgParsing
and JekyllBlockNoArgParsing
subclasses cannot.
This feature is usually only desired for JekyllBlock
subclasses.
- When used as a keyword option, a default value is used for the attribution string.
- When used as a name/value option, the attribution string can be specified.
Using the attribution
option cause subclasses to replace their usual output with HTML that looks like:
<div id="jps_attribute_12345" class="jps_attribute">
<a href="https://github.com/mslinn/jekyll_outline">
<b>Generated by <code>jekyll_outline</code>.
</a>
</div>
The id
attribute is in the sample HTML above is randomized so more than one attribution can appear on a page.
Attribution Generation
You can decide where you want the attribution string for your Jekyll tag to appear by invoking @helper.attribute
.
For example, this is how the
jekyll_outline
tag generates output:
<<~HEREDOC
<div class="outer_posts">
#{make_entries(collection)&.join("\n")}
</div>
#{@helper.attribute if @helper.attribution}
HEREDOC
Usage
Typical usage for the attribution
tag is:
{% my_block_tag attribution %}
Content of my_block_tag.
{% endmy_block_tag %}
The normal processing of my_block_tag
is augmented by interpolating the attribution format string,
which is a Ruby-compatible interpolated string.
The default attribution format string is:
"Generated by the #{name} #{version} Jekyll plugin, written by #{author} #{date}."
Because jekyll_plugin_suppprt
subclasses are gem
s, their gemfile
s define values for
name
, version
, homepage
, and authors
, as well as many other properties.
The date
property is obtained from the plugin/gem publishing date.
An alternative attribution string can be specified properties can be output using any of the above properties:
{% my_tag attribution="Generated by the #{name} #{version} Jekyll plugin, written by #{author} #{date}" %}
Subclassing
Jekyll plugins created using jekyll_plugin_support
are implemented as Ruby classes.
If you would like to create a version of an existing Jekyll plugin, you will need to subclass the plugin.
In order to do that, you will need to override the plugin name and version, which are defined as constants.
Jekyll_plugin_support
provides a method that allows
a constant to be redefined, called redef_without_warning
.
Use it in a subclass like this:
redef_without_warning :PLUGIN_NAME, 'my_plugin'.freeze
redef_without_warning :VERSION, '0.1.0'.freeze
Development
After checking out the jekyll_plugin_suppprt
repository, run bin/setup
to install dependencies.
bin/console
provides an interactive prompt that allows you to experiment.
To build and install this gem onto your local machine, run:
$ bundle exec rake install
jekyll_plugin_support 0.1.0 built to pkg/jekyll_plugin_support-0.1.0.gem.
jekyll_plugin_support (0.1.0) installed.
Examine the newly built gem:
$ gem info jekyll_plugin_support
*** LOCAL GEMS ***
jekyll_plugin_support (0.1.0)
Author: Mike Slinn
Homepage:
https://github.com/mslinn/jekyll_plugin_support
License: MIT
Installed at: /home/mslinn/.gems
Provides support for writing Jekyll plugins.
Pry Breakpoint On StandardError
A pry
breakpoint will be set in the StandardError
handler if pry_on_standard_error: true
is set in variable configuration section of _config.yml
.
For example, if your plugin is called blah
, enable the breakpoint with the following section:
blah:
pry_on_standard_error: true
Demonstration Plugins and Website
A demo / test website is provided in the demo
directory.
It can be used to debug the plugin or to run freely.
Run Freely
-
Run from the command line:
$ demo/_bin/debug -r
-
View the generated website, which might be at
http://localhost:4444
, depending on how you configured it.
Plugin Debugging
-
Set breakpoints in Visual Studio Code.
-
Initiate a debug session from the command line by running the
demo/_bin/debug
script:$ demo/_bin/debug Fetching gem metadata from https://rubygems.org/.......... Resolving dependencies... Fetching public_suffix 5.0.4 Fetching nokogiri 1.15.5 (x86_64-linux) Installing public_suffix 5.0.4 Installing nokogiri 1.15.5 (x86_64-linux) Bundle complete! 17 Gemfile dependencies, 96 gems now installed. Use `bundle info [gemname]` to see where a bundled gem is installed. INFO PluginMetaLogger: Loaded DraftFilter plugin. INFO PluginMetaLogger: Loaded outline_js v1.2.1 plugin. INFO PluginMetaLogger: Loaded outline v1.2.1 plugin. Configuration file: /mnt/f/jekyll_plugin_support/demo/_config.yml Cleaner: Removing /mnt/f/jekyll_plugin_support/demo/_site... Cleaner: Removing /mnt/f/jekyll_plugin_support/demo/.jekyll-metadata... Cleaner: Removing /mnt/f/jekyll_plugin_support/demo/.jekyll-cache... Cleaner: Nothing to do for .sass-cache. DEBUGGER: Debugger can attach via TCP/IP (127.0.0.1:37177) DEBUGGER: wait for debugger connection...
-
Once the
DEBUGGER: wait for debugger connection...
message appears, run the Visual Studio Code launch configuration calledAttach with rdbg
. -
View the generated website, which might be at
http://localhost:4444
, depending on how you configured it.
Build and Push to RubyGems
To release a new version:
-
Update the version number in
version.rb
. -
Add an entry to
CHANGELOG.md
describing the changes since the previous version. -
Commit all changes to git; if you don't the next step might fail with an unexplainable error message.
-
Run the following:
$ bundle exec rake release
The above creates a git tag for the version, commits the created tag, and pushes the new
.gem
file to RubyGems.org.
Contributing
- Fork the project
- Create a descriptively named feature branch
- Add your feature
- Submit a pull request
License
The gem is available as open source under the terms of the MIT License.