sbt-site supports simple variable and Regular Expression substitution via the PreprocessPlugin if for example you need to replace a version string in a source file or a generated HTML file. More advanced preprocessing, such as interpreting code snippets with tut, is possible via additional configuration as shown below.


The PreprocessPlugin reads files from an input directory, substitute variables and writes them to an output directory. In addition to preprocessing static content it is also possible to use the plugin either before or after invoking a site generator. To enable, add this to your build.sbt file:


By default files are read from src/site-preprocess but this is configurable by setting sourceDirectory:

sourceDirectory in Preprocess := sourceDirectory.value / "site-preprocess"

Variables are delimited by surrounding the name with @ symbols (e.g. @[email protected]). Values are assigned to variables via the setting preprocessVars: Map[String, String]. For example:

preprocessVars in Preprocess := Map("VERSION" -> version.value, "DATE" -> new Date().toString)

The plugin will generate an error if a variable is found in the source file with no matching value in preprocessVars.

More advanced substitution patterns can be used by providing Regular Expression rules via the setting preprocessRules: Seq[(Regex, Match => String)]. For example Scaladoc used to (before 2.12.9 and 2.13.0) prepend “.scala” to source links of Java files. The following preprocessing rule will find and fix such links:

preprocessRules in Preprocess := Seq(
  ("\\.java\\.scala".r, _ => ".java")

The setting preprocessIncludeFilter is used to define the filename extensions that should be processed when makeSite is run.

preprocessIncludeFilter := "*.md" | "*.markdown"

The default filter is:

"*.txt" | "*.html" | "*.md" | "*.rst"

Preprocessing Markdown files with tut

The tut sbt plugin allows you to write documentation with fenced code blocks that is typechecked and run as part of your build. For example this markdown snippet:

Here is how you add numbers:

1 + 1

Will show the result of running the code in the Scala REPL:

Here is how you add numbers:

scala> 1 + 1
res0: Int = 2    

The following example shows how to use it to preprocess a collection of markdown files before running a site generator.

enablePlugins(ParadoxPlugin, ParadoxSitePlugin, TutPlugin)
sourceDirectory in (Compile, paradox) := tutTargetDirectory.value
makeSite := makeSite.dependsOn(tut).value

The example uses the Paradox site generator but can be adapted to any site generator which understands markdown by configuring its sourceDirectory accordingly. For Jekyll, this would be:

Jekyll / sourceDirectory := tutTargetDirectory.value