• the project has the following structure:
  the top directory contains following folders:
  -master/pom.xml <- parent pom, contains module(s)
  -module1/pom.xml <- module pom
  -roots_to_add/... <- directory containing 2 subdirectories - src and test - to be added using build-helper plugin

the pom.xml of module module1 contains following:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <version>1.0</version>
    <executions>
        <execution>
            <id>add extra sources</id>
            <goals>
                <goal>add-source</goal>
            </goals>
            <configuration>
                <sources>
                    <source>../sources_to_add/src</source>
                </sources>
            </configuration>
        </execution>
        <execution>
            <id>add extra test sources</id>
            <goals>
                <goal>add-test-source</goal>
            </goals>
            <configuration>
                <sources>
                    <source>../sources_to_add/test</source>
                </sources>
            </configuration>
        </execution>
    </executions>
</plugin>

Try to open master/pom.xml as idea project: exception, project is not open. The ipr file is created, but no modules etc.

Error during dispatching of java.awt.event.MouseEvent[MOUSE_RELEASED,(38,48),absolute(55,101),button=1,modifiers=Button1,clickCount=1] on ###overrideRedirect###: Argument 0 for @NotNull parameter of com/intellij/openapi/util/io/FileUtil.toSystemIndependentName must not be null
java.lang.IllegalArgumentException: Argument 0 for @NotNull parameter of com/intellij/openapi/util/io/FileUtil.toSystemIndependentName must not be null
at com.intellij.openapi.util.io.FileUtil.toSystemIndependentName(FileUtil.java)
at org.jetbrains.idea.maven.core.util.Path.<init>(Path.java:12)
at org.jetbrains.idea.maven.project.RootModelAdapter.toUrl(RootModelAdapter.java:107)
at org.jetbrains.idea.maven.project.RootModelAdapter.addSourceDir(RootModelAdapter.java:83)
at org.jetbrains.idea.maven.project.MavenToIdeaModuleConfigurator.addBuildHelperPluginSource(MavenToIdeaModuleConfigurator.java:145)
at org.jetbrains.idea.maven.project.MavenToIdeaModuleConfigurator.configBuildHelperPluginSources(MavenToIdeaModuleConfigurator.java:134)
at org.jetbrains.idea.maven.project.MavenToIdeaModuleConfigurator.configFolders(MavenToIdeaModuleConfigurator.java:81)
at org.jetbrains.idea.maven.project.MavenToIdeaModuleConfigurator.configModule(MavenToIdeaModuleConfigurator.java:63)
at org.jetbrains.idea.maven.project.MavenToIdeaModuleConfigurator.config(MavenToIdeaModuleConfigurator.java:58)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator.convertNode(MavenToIdeaConfigurator.java:97)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator.access$000(MavenToIdeaConfigurator.java:18)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator$2.visit(MavenToIdeaConfigurator.java:83)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator$2.visit(MavenToIdeaConfigurator.java:79)
at org.jetbrains.idea.maven.core.util.Tree.visit(Tree.java:54)
at org.jetbrains.idea.maven.core.util.Tree.visit(Tree.java:74)
at org.jetbrains.idea.maven.project.MavenProjectModel.visit(MavenProjectModel.java:193)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator.configModules(MavenToIdeaConfigurator.java:79)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator.config(MavenToIdeaConfigurator.java:54)
at org.jetbrains.idea.maven.project.MavenToIdeaConfigurator.config(MavenToIdeaConfigurator.java:34)
at org.jetbrains.idea.maven.project.MavenImportProcessor$3.run(MavenImportProcessor.java:111)
at com.intellij.openapi.application.impl.ApplicationImpl.runWriteAction(ApplicationImpl.java:69)
at org.jetbrains.idea.maven.project.MavenImportProcessor.commit(MavenImportProcessor.java:109)
at org.jetbrains.idea.maven.project.action.MavenImportBuilder.commit(MavenImportBuilder.java:75)
at com.intellij.projectImport.ProjectOpenProcessorBase.doOpenProject(ProjectOpenProcessorBase.java:9)
at com.intellij.ide.impl.ProjectUtil.openOrImport(ProjectUtil.java:26)
at com.intellij.ide.actions.OpenProjectAction.actionPerformed(OpenProjectAction.java:2)
at com.intellij.openapi.actionSystem.impl.ActionMenuItem$ActionTransmitter.actionPerformed(ActionMenuItem.java:13)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at com.intellij.openapi.actionSystem.impl.ActionMenuItem.fireActionPerformed(ActionMenuItem.java:55)
at com.intellij.ui.plaf.beg.BegMenuItemUI.a(BegMenuItemUI.java:244)
at com.intellij.ui.plaf.beg.BegMenuItemUI.access$300(BegMenuItemUI.java:104)
at com.intellij.ui.plaf.beg.BegMenuItemUI$MyMouseInputHandler.mouseReleased(BegMenuItemUI.java:8)
at java.awt.Component.processMouseEvent(Component.java:6041)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
at java.awt.Component.processEvent(Component.java:5806)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4413)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4243)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
at java.awt.Container.dispatchEventImpl(Container.java:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2440)
at java.awt.Component.dispatchEvent(Component.java:4243)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at com.intellij.ide.IdeEventQueue.c(IdeEventQueue.java:64)
at com.intellij.ide.IdeEventQueue.b(IdeEventQueue.java:124)
at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.java:205)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)