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Intellij comes ready-equipped to support Daffodil with only a few changed required to add the plugins for Scala and SBT support.
In order to make sure all the required libraries, including Scala, are downloaded you should first run sbt from the command line. This will call Ivy to retrieve any missing libraries so that when you run Intellij you can point to the right libraries for the project build.
Next, in In the Intellij UI, open File->Settings and in the left pane scroll down to the section labeled Plugins (this is below the middle divider). In plugins select "Browse repositories,,," and from this list select "Scala" and "SBT" (use the search feature to help find them). Then click the Download and install icon (the disk with the arrow toolbar button or via context menu). When the two plugins are loaded, close Intellij and restart.
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