Hover provider for crossrefs

packages/langium/src/default-module.ts

@@ -14,7 +14,7 @@ import { DefaultDocumentHighlighter } from './lsp/document-highlighter';
 import { DefaultDocumentSymbolProvider } from './lsp/document-symbol-provider';
 import { DefaultFoldingRangeProvider } from './lsp/folding-range-provider';
 import { DefaultGoToResolverProvider } from './lsp/goto';
-import { MultilineCommentHoverProvider } from './lsp/hover-provider';
+import { LangiumGrammarHoverProvider } from './lsp/langium-grammar-hover-provider';
 import { DefaultReferenceFinder } from './lsp/reference-finder';
 import { DefaultRenameHandler } from './lsp/rename-refactoring';
 import { createLangiumParser } from './parser/langium-parser-builder';
@@ -62,7 +62,7 @@ export function createDefaultModule(context: DefaultModuleContext): Module<Langi
                 RuleInterpreter: () => new RuleInterpreter()
             },
             DocumentSymbolProvider: (services) => new DefaultDocumentSymbolProvider(services),
-            HoverProvider: (services) => new MultilineCommentHoverProvider(services),
+            HoverProvider: (services) => new LangiumGrammarHoverProvider(services),
             FoldingRangeProvider: (services) => new DefaultFoldingRangeProvider(services),
             ReferenceFinder: (services) => new DefaultReferenceFinder(services),
             GoToResolver: (services) => new DefaultGoToResolverProvider(services),

packages/langium/src/lsp/langium-grammar-hover-provider.ts

@@ -0,0 +1,74 @@
+/******************************************************************************
+ * Copyright 2021 TypeFox GmbH
+ * This program and the accompanying materials are made available under the
+ * terms of the MIT License, which is available in the project root.
+ ******************************************************************************/
+import { Hover, HoverParams } from 'vscode-languageserver';
+import {CrossReference, findLeafNodeAtOffset, findNameAssignment, Grammar, isCrossReference, isParserRule, isType, LangiumDocuments, LangiumServices, RuleCall } from '..';
+import { AstNode } from '../syntax-tree';
+import { findRelevantNode } from '../utils/cst-util';
+import { MaybePromise } from '../utils/promise-util';
+import { LangiumDocument } from '../workspace/documents';
+import { MultilineCommentHoverProvider } from './hover-provider';
+
+export class LangiumGrammarHoverProvider extends MultilineCommentHoverProvider {
+
+    readonly grammar: Grammar;
+    readonly documents: LangiumDocuments;
+    constructor(services: LangiumServices) {
+        super(services);
+        this.grammar = services.Grammar;
+        this.documents = services.shared.workspace.LangiumDocuments;
+    }
+
+    getHoverContent(document: LangiumDocument<AstNode>, params: HoverParams): MaybePromise<Hover | undefined> {
+        const rootNode = document.parseResult?.value?.$cstNode;
+        if(rootNode)  {
+            const offset = document.textDocument.offsetAt(params.position);
+            const cstNode = findLeafNodeAtOffset(rootNode, offset);
+            if(cstNode){
+                const relevantNode = findRelevantNode(cstNode);
+                if(isCrossReference(relevantNode)){
+                    return this.getCrossReferenceHoverContent(relevantNode);
+                } else {
+                    return super.getHoverContent(document, params);
+                }
+            }
+        }
+        return undefined;
+    }
+
+    getCrossReferenceHoverContent(node: CrossReference): MaybePromise<Hover | undefined> {
+
+        const ref = node.type.ref;
+
+        if(ref){
+            if(isType(ref)){
+                return {
+                    contents: {
+                        kind: 'markdown',
+                        value: ref.$cstNode!.text
+                    }
+                };
+            }
+            else if(isParserRule(ref)){
+                let terminal;
+                if(node.$cstNode?.text.includes(':')){
+                    terminal = node.$cstNode?.text.split(':')[1].replace(']', '');
+                } else {
+                    terminal = (findNameAssignment(ref)?.terminal as RuleCall).rule.$refText;
+                }
+
+                return {
+                    contents: {
+                        kind: 'markdown',
+                        value: `[${ref.name}:${terminal}]`,
+                    },
+                };
+            }
+        }
+
+        return undefined;
+    }
+
+}