feat: Added a file view provider for LSP files that yields fake PSI elements for words.

src/main/java/com/redhat/devtools/lsp4ij/features/documentSymbol/LSPDocumentFileViewProviderFactory.java

@@ -0,0 +1,78 @@
+/*******************************************************************************
+ * Copyright (c) 2020 Red Hat, Inc.
+ * Distributed under license by Red Hat, Inc. All rights reserved.
+ * This program is made available under the terms of the
+ * Eclipse Public License v2.0 which accompanies this distribution,
+ * and is available at https://www.eclipse.org/legal/epl-v20.html
+ *
+ * Contributors:
+ * Red Hat, Inc. - initial API and implementation
+ ******************************************************************************/
+
+package com.redhat.devtools.lsp4ij.features.documentSymbol;
+
+import com.intellij.lang.Language;
+import com.intellij.openapi.editor.Document;
+import com.intellij.openapi.project.Project;
+import com.intellij.openapi.util.TextRange;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.psi.*;
+import com.redhat.devtools.lsp4ij.LSPIJUtils;
+import com.redhat.devtools.lsp4ij.features.LSPPsiElement;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * File view provider factory for LSP files that yields simple PSI elements for the word under the caret. This helps
+ * with a number of plugin SDK EPs that need to find distinct elements.
+ */
+public class LSPDocumentFileViewProviderFactory implements FileViewProviderFactory {
+
+    @Override
+    @NotNull
+    public FileViewProvider createFileViewProvider(@NotNull VirtualFile virtualFile,
+                                                   Language language,
+                                                   @NotNull PsiManager manager,
+                                                   boolean eventSystemEnabled) {
+        Project project = manager.getProject();
+        if (!project.isDisposed() && !virtualFile.isDirectory() && virtualFile.isValid()) {
+            // NOTE: We can't filter by LSP here, so we just have to make sure that this view provider behaves as the
+            // standard view provider for non-LSP files
+            return new LSPDocumentFileViewProvider(manager, virtualFile, eventSystemEnabled);
+        }
+
+        return new SingleRootFileViewProvider(manager, virtualFile, eventSystemEnabled);
+    }
+
+    private static class LSPDocumentFileViewProvider extends SingleRootFileViewProvider {
+        public LSPDocumentFileViewProvider(@NotNull PsiManager manager,
+                                           @NotNull VirtualFile virtualFile,
+                                           boolean eventSystemEnabled) {
+            super(manager, virtualFile, eventSystemEnabled);
+        }
+
+        @Override
+        public PsiElement findElementAt(int offset) {
+            VirtualFile virtualFile = getVirtualFile();
+            Project project = getManager().getProject();
+            PsiFile file = LSPIJUtils.getPsiFile(virtualFile, project);
+            // TODO: How can we quickly and simply check whether this is an LSP4IJ-managed file?
+            if (file != null) {
+                Document document = LSPIJUtils.getDocument(file);
+                if (document != null) {
+                    TextRange wordTextRange = LSPIJUtils.getWordRangeAt(document, file, offset);
+                    if (wordTextRange != null) {
+                        return new LSPPsiElement(file, wordTextRange) {
+                            @Override
+                            // NOTE: We have to report this as physical even though it's not
+                            public boolean isPhysical() {
+                                return true;
+                            }
+                        };
+                    }
+                }
+            }
+
+            return super.findElementAt(offset);
+        }
+    }
+}

src/main/resources/META-INF/plugin.xml

@@ -274,6 +274,14 @@ L
                 id="LSPDocumentLinkGotoDeclarationHandler"
                 implementation="com.redhat.devtools.lsp4ij.features.documentLink.LSPDocumentLinkGotoDeclarationHandler"/>
 
+        <!-- LSP file view provider to yield some PSI structure to otherwise flat files -->
+        <lang.fileViewProviderFactory
+                language="TEXT"
+                implementationClass="com.redhat.devtools.lsp4ij.features.documentSymbol.LSPDocumentFileViewProviderFactory"/>
+        <lang.fileViewProviderFactory
+                language="textmate"
+                implementationClass="com.redhat.devtools.lsp4ij.features.documentSymbol.LSPDocumentFileViewProviderFactory"/>
+
         <!-- LSP textDocument/documentSymbol request support -->
         <lang.psiStructureViewFactory
                 id="LSPDocumentSymbolStructureViewFactoryForText"