Soupault 1.8.0 release, with improved plugin support

Estimated reading time: 2 minutes.


Soupault 1.8.0 is available for download. This release is focused on improving plugin support. First big improvement is that Lua plugin execution errors are treated exactly like all other errors: in strict mode, they fail the build. There's also a bunch of new plugin functions.

Now to the improvements…

Plugin execution error handling

In older versions, Lua syntax errors and runtime errors were logged, but they could not stop the build even in strict mode. That was a limitation of Lua-ML, so I had to fix it there.

Now plugin errors correctly fail the build.

TARGET_DIR environment variable

One possible use of plugins and executable called with the preprocess_element widget is processing existing assets or creating new ones.

For example, it’s quite easy to resize images to their width and height attributes, create PNG versions of Graphviz graphs, or run chunks of the page through a text to speech program.

However, one thing was overlooked in 1.7.0: there was no easy way to see where the page file will be stored and create correct relative links. Directory structure varies depending on the clean_urls option, so you’d have to put all generated files in a single directory and use absolute paths.

Now there is: programs called from preprocess_element and exec widgets can access it via TARGET_DIR environment variable, and Lua plugins got a target_dir global.

Now you can easily store processed/generated assets together with pages:

  widget = 'preprocess_element'
  selector = '.graphviz-png'
  command = 'dot -Tpng > $TARGET_DIR/graph_$ATTR_ID.png && echo \<img src="graph_$ATTR_ID.png"\>'
  action = 'replace_element'

For example, when this widget runs on site/articles/dijkstra.html and encounters <pre class="graphviz-png" id="sample">, it will save the PNG version to build/articles/dijkstra/graph_sample.png if clean URLs are on, or to build/articles/graph_sample.png if not. In both cases relative src will work as expected.

Build profiles

Sometimes you may want to enable certain widgets only for some builds. For example, include analytics scripts only in production builds.

Now it’s easy to do. Add a profile option to your widget:

  profile = "live"
  widget = "include"
  file = "includes/analytics.html"
  selector = "body"

Then soupault will only process that widget if you run soupault --profile live. If you run soupault --profile dev, or just soupault, it will ignore that widget.

Specifying minimum supported version in plugins

It can be frustrating to see a plugin fail mysteriously and then find out it simply wants a newer version.

Now it’s easy to specify minimum supported version:


If soupault version is less than 42.0.0, the build will fail like this:

[ERROR] Could not process page site/index.html: Plugin requires soupault 42.0.0 or newer, current version is 1.8.0

You can specify either a full version like 1.8.0, but you can also write 1.8 and it’s assumed to mean 1.8.0.

There is no way to specify maximum supported version, but if I make any incompatible change to soupault, I will add a function for that.

Plugins that use Plugin.require_version will obviously fail to work with versions older than 1.8.8 because they didn’t have that function. For this reason you should only use it in new plugins that rely on functions introduced in 1.8.0 or later.

New plugin functions

Most of these are not really new, but rather internal functions now available to plugins.

Generates a random integer number from 0 to max. Example: `Sys.random(100)`. Numbers are not cryptographically secure.
Executes a command in the system shell (/bin/sh on UNIX, cmd.exe on Windows) and returns its output. Execution errors are logged to stderr.
If settings.debug is true, shows a message in the build log. Otherwise does nothing.
HTML.replace_element and HTML.delete_element
Aliases for HTML.replace and HTML.delete added for consistency.
Removes extra spaces from a string.
Removes all characters other than English letters and digits from a string and replaces them with hyphens.