sass-maven-plugin does not compile scss files - maven

Question

I try to integrate scss conversion into our existing maven project.
I tried to add
<plugin>
<groupId>nl.geodienstencentrum.maven</groupId>
<artifactId>sass-maven-plugin</artifactId>
<version>${maven.sass.plugin.version}</version>
<executions>
<execution>
<id>generate-css</id>
<phase>generate-resources</phase>
<goals>
<goal>update-stylesheets</goal>
</goals>
<configuration>
<sassOptions>
<always_update>true</always_update>
</sassOptions>
<includes>
<include>${scssSourceInclude}</include>
</includes>
<sassSourceDirectory>${project.basedir}/src/main/webapp/scss</sassSourceDirectory>
<destination>${project.build.directory}/${project.build.finalName}/css</destination>
<!-- <destination>${project.basedir}/src/main/webapp/css</destination> -->
</configuration>
</execution>
</executions>
</plugin>
When I run mvn clean install command, it compiles correctly for destination which is set to "target" directory:
[INFO] --- sass-maven-plugin:2.12:update-stylesheets (generate-css) # ui.web ---
[INFO] Checked 1 files for d:\work\git\repository\project\src\main\webapp\scss
[INFO] Checked 0 files for d:\work\git\repository\project\target\ui.web\css
[INFO] Compiling Sass templates
[INFO] No resource element was specified, using short configuration.
[INFO] Queueing Sass template for compile: d:\work\git\repository\project/src/main/webapp/scss => d:\work\git\repository\project/target/ui.web/css
...
In case of using second (commented) destination it skips scss compilation:
[INFO] --- sass-maven-plugin:2.12:update-stylesheets (generate-css) # ui.web ---
[INFO] Checked 1 files for d:\work\git\repository\project\src\main\webapp\scss
[INFO] Checked 959 files for d:\work\git\repository\project\src\main\webapp\css
[INFO] Skip compiling Sass templates, no changes.
The only difference is that I need generated css files in src directories due to further processing (minification, concatenation, adding licence header, etc.)
Dir structure:
src
|-main
|-webapp
|-scss
|- common.scss
|- app.scss
|- admin
|- admin.scss
|-css
Can somebody explain to me why the files are not processed into src directories? Is there some missing configuration which I should apply?

Answer 1

I think your problem would be solved by upgrading version 2.22 or later. Here's why:
The console output of the build with <destination>${project.basedir}/src/main/webapp/css</destination> shows that you already have 959 files in the destination directory. Given that you have only a single file in src/main/webapp/scss I'm assuming that most of the 959 files in src/main/webapp/css are normal, non-generated CSS files and that you intend to add those generated by the plugin.
Looking at the source of the plugin, in versions prior to 2.22, the criteria for building given that files exist in both source and destination directories is that the source directory tree has a file younger than any of the files in the destination directory. See UpdateStylesheetsMojo#buildRequired() for the 2.12 implementation. Note that the plugin does not compare source and destination files by name, it only compares "extreme" timestamps. I suspect that the build that skips compilation finds no file in src/main/webapp/scss that are younger than all files in src/main/webapp/css. You could test my hypothesis by modifying one of the .scss files before building. Issue #136: Wrong "build required" analysis when source and destination are the same describes a very similar problem. This is solved by pull request #137:
add css filter at destination when checking buildrequired which is part of version 2.22. This should make your build actually compile .scss files even in the face of newer .css files in the destination directory.
Stepping back a bit, I would advise against modifying src/ during the build. As stated in Introduction to the Standard Directory Layout
The src directory contains all of the source material for building the project [...]
whereas
The target directory is used to house all output of the build.
Behavior is built around this convention. For example mvn clean removes target/ (or more generally ${project.build.directory}). It makes no attempt at removing files generated within src/. Looking at a developer reply on the issue mentioned above it's pretty clear that the developers of the plugin share this sentiment:
Why would anyone want to mix source code and compiled code at all?
Considering this convention, I would recommend you move the .scss files to src/main/sass (the default value of sassSourceDirectory) and let the plugin output .css files to e.g. ${project.build.directory}/generated-css-resources. Then let the plugins handling minification, concatenation and license header operate on this directory as well as src/main/webapp/css. If they don't support this with configuration, you can still likely achieve this with two executions of the plugins, one for each directory. An alternative is to aggregate the generated and non-generated .css files in a directory ${project.build.directory}/aggregated-css with the help of Maven Resources Plugin's copy-resources goal, making sure the generated come first, to avoid the initial problem, and use this directory as input to further processing. I'm sure there are other ways to solve this problem as well.

Answer 2

I am not sure about the solution, but I tried the workaround mentioned in this post https://github.com/jruby/jruby/issues/2498 and it worked for me.
Basically downgrade the sass-maven-plugin version to 2.0 and it should work.