Merge pull request #36 from elm-tooling/fix-33-expose

Fix IDE crash on expose

Author: ahankinson

src/main/kotlin/org/elm/ide/intentions/ElmAtCaretIntentionActionBase.kt

@@ -41,6 +41,8 @@ abstract class ElmAtCaretIntentionActionBase<Ctx> : BaseElementAtCaretIntentionA
 
     abstract fun invoke(project: Project, editor: Editor, context: Ctx)
 
+    override fun startInWriteAction(): Boolean = true
+
     final override fun invoke(project: Project, editor: Editor, element: PsiElement) {
         val context = findApplicableContext(project, editor, element) ?: return
         checkWriteAccessAllowed()
@@ -51,4 +53,4 @@ abstract class ElmAtCaretIntentionActionBase<Ctx> : BaseElementAtCaretIntentionA
         checkReadAccessAllowed()
         return findApplicableContext(project, editor, element) != null
     }
-}
+}

src/main/kotlin/org/elm/openapiext/Utils.kt

@@ -21,6 +21,7 @@ import com.intellij.openapi.vfs.VirtualFile
 import com.intellij.openapi.vfs.VirtualFileManager
 import com.intellij.psi.PsiFile
 import com.intellij.psi.PsiManager
+import com.intellij.codeInsight.intention.preview.IntentionPreviewUtils
 import org.jdom.Element
 import org.jdom.input.SAXBuilder
 import java.nio.file.Path
@@ -38,6 +39,9 @@ val Project.modules: Collection<Module>
 
 
 fun checkWriteAccessAllowed() {
+    // In preview we must not assert write access; the platform runs without it.
+    if (IntentionPreviewUtils.isIntentionPreviewActive()) return
+
     check(ApplicationManager.getApplication().isWriteAccessAllowed) {
         "Needs write action"
     }