Fix eclipse error reporting

org.lflang/src/org/lflang/FileConfig.java

@@ -7,6 +7,7 @@
 import java.util.function.Consumer;
 
 import org.eclipse.core.resources.IProject;
+import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.ResourcesPlugin;
 import org.eclipse.emf.common.util.URI;
 import org.eclipse.emf.ecore.resource.Resource;
@@ -66,6 +67,16 @@ public class FileConfig {
      */
     public final Resource resource;
 
+    /**
+     * If running in an Eclipse IDE, the iResource refers to the
+     * IFile representing the Lingua Franca program.
+     * This is the XText view of the file, which is distinct
+     * from the Eclipse eCore view of the file and the OS view of the file.
+     *
+     * This is null if running outside an Eclipse IDE.
+     */
+    public final IResource iResource;
+
     /**
      * The full path to the file containing the .lf file including the
      * full filename with the .lf extension.
@@ -138,6 +149,8 @@ public FileConfig(Resource resource, Path srcGenBasePath, boolean useHierarchica
 
         Path binRoot = outPath.resolve(DEFAULT_BIN_DIR);
         this.binPath = useHierarchicalBin ? binRoot.resolve(getSubPkgPath(srcPath)) : binRoot;
+
+        this.iResource = FileUtil.getIResource(resource);
     }
 
     /**

org.lflang/src/org/lflang/generator/EclipseErrorReporter.java

@@ -36,6 +36,7 @@
 import org.eclipse.emf.ecore.EObject;
 import org.eclipse.xtext.diagnostics.Severity;
 import org.eclipse.xtext.validation.EObjectDiagnosticImpl;
+
 import org.lflang.ErrorReporter;
 import org.lflang.FileConfig;
 import org.lflang.util.FileUtil;
@@ -113,10 +114,7 @@ private String report(String message, Severity severity, Integer line, Path file
 
         // Create a marker in the IDE for the error.
         // See: https://help.eclipse.org/2020-03/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Fguide%2FresAdv_markers.htm
-        final IResource iResource = file != null
-                ? FileUtil.getIResource(file)
-                : FileUtil.getIResource(fileConfig.resource);
-
+        IResource iResource = file != null ? FileUtil.getIResource(file) : fileConfig.iResource;
         try {
             IMarker marker = iResource.createMarker(IMarker.PROBLEM);
 

org.lflang/src/org/lflang/util/FileUtil.java

@@ -357,8 +357,8 @@ public static void deleteDirectory(Path dir) throws IOException {
      * Get the iResource corresponding to the provided resource if it can be
      * found.
      */
-    public static IResource getIResource(Resource r)  {
-        return getIResource(java.net.URI.create(r.getURI().toString()));
+    public static IResource getIResource(Resource r) throws IOException {
+        return getIResource(FileUtil.toPath(r).toFile().toURI());
     }
 
     /**
@@ -371,20 +371,25 @@ public static IResource getIResource(Path path) {
     /**
      * Get the specified uri as an Eclipse IResource or null if it is not found.
      *
+     * Also returns null if this is not called from within a running Eclipse instance.
+     *
      * @param uri A java.net.uri of the form "file://path".
      */
     public static IResource getIResource(java.net.URI uri) {
-        IResource resource = null;
         // For some peculiar reason known only to Eclipse developers,
         // the resource cannot be used directly but has to be converted
         // a resource relative to the workspace root.
-        IWorkspaceRoot workspaceRoot = ResourcesPlugin.getWorkspace().getRoot();
+        try {
+            IWorkspaceRoot workspaceRoot = ResourcesPlugin.getWorkspace().getRoot();
 
-        IFile[] files = workspaceRoot.findFilesForLocationURI(uri);
-        if (files != null && files.length > 0 && files[0] != null) {
-            resource = files[0];
+            IFile[] files = workspaceRoot.findFilesForLocationURI(uri);
+            if (files != null && files.length > 0 && files[0] != null) {
+                return files[0];
+            }
+        } catch (IllegalStateException e) {
+            // We are outside of Eclipse.
         }
-        return resource;
+        return null;
     }
 
     /**