Once you open a project in the IDE you have to select a Maven profile (in Maven tab): it should be kotlin-js or kotlin-jvm, you shouldn't enable both otherwise IDEA inspections will not work.

You can build the project only using Maven. If you run Maven via the IDEA runner please ensure you have -Pkotlin-js,kotlin-jvm in the command line

You have to install shared module before build other dependant submodules. Don't forget to reinstall shared once you have changed something in shared

You can build all by maven by command line

./mvnw clean package

If some tag or attribute is missing then

• look at buildSrc/src/main/resources/html_5.xsd
• modify it accordingly
• In the Gradle task view, go to source-generation and execute the generate task
• In the Gradle task view, go to verification and execute the allTests task

See commit Add figcaption element for an example