feat(vscode): Add completions for Grain Doc comments (#80)

editor-extensions/vscode/client/src/GrainDocCompletionProvider.ts

@@ -0,0 +1,65 @@
+// Based on https://github.com/microsoft/vscode/blob/94c9ea46838a9a619aeafb7e8afd1170c967bb55/extensions/typescript-language-features/src/languageFeatures/jsDocCompletions.ts
+import * as vscode from "vscode";
+import { LanguageClient } from "vscode-languageclient";
+
+const defaultGrainDoc = new vscode.SnippetString(`/**\n * $0\n */`);
+
+class GrainDocCompletionItem extends vscode.CompletionItem {
+  constructor(
+    public readonly document: vscode.TextDocument,
+    public readonly position: vscode.Position
+  ) {
+    super("/** */", vscode.CompletionItemKind.Text);
+    this.detail = "Grain Doc Comment";
+    this.sortText = "\0";
+
+    const line = document.lineAt(position.line).text;
+    const prefix = line.slice(0, position.character).match(/\/\**\s*$/);
+    const suffix = line.slice(position.character).match(/^\s*\**\//);
+    const start = position.translate(0, prefix ? -prefix[0].length : 0);
+    const range = new vscode.Range(
+      start,
+      position.translate(0, suffix ? suffix[0].length : 0)
+    );
+    this.range = { inserting: range, replacing: range };
+  }
+}
+
+export class GrainDocCompletionProvider
+  implements vscode.CompletionItemProvider {
+  constructor(readonly client: LanguageClient) {}
+
+  public async provideCompletionItems(
+    document: vscode.TextDocument,
+    position: vscode.Position,
+    token: vscode.CancellationToken
+  ): Promise<vscode.CompletionItem[] | undefined> {
+    if (!this.isPotentiallyValidDocCompletionPosition(document, position)) {
+      return undefined;
+    }
+
+    const item = new GrainDocCompletionItem(document, position);
+
+    // TODO: Get param and returns details from `grain lsp`
+    item.insertText = defaultGrainDoc;
+
+    return [item];
+  }
+
+  private isPotentiallyValidDocCompletionPosition(
+    document: vscode.TextDocument,
+    position: vscode.Position
+  ): boolean {
+    // Only show the GrainDoc completion when the everything before the cursor is whitespace
+    // or could be the opening of a comment
+    const line = document.lineAt(position.line).text;
+    const prefix = line.slice(0, position.character);
+    if (!/^\s*$|\/\*\*\s*$|^\s*\/\*\*+\s*$/.test(prefix)) {
+      return false;
+    }
+
+    // And everything after is possibly a closing comment or more whitespace
+    const suffix = line.slice(position.character);
+    return /^\s*(\*+\/)?\s*$/.test(suffix);
+  }
+}

editor-extensions/vscode/client/src/extension.ts

@@ -16,12 +16,14 @@ import {
 } from "vscode-languageclient";
 
 import { CodelensProvider } from "./CodelensProvider";
+import { GrainDocCompletionProvider } from "./GrainDocCompletionProvider";
 
 let client: LanguageClient;
 
 let disposables: Disposable[] = [];
 
 let codelensProvider: CodelensProvider;
+let grainDocCompletionProvider: GrainDocCompletionProvider;
 
 export function activate(context: ExtensionContext) {
   // The server is implemented in node
@@ -68,6 +70,13 @@ export function activate(context: ExtensionContext) {
     codelensProvider = new CodelensProvider(client);
     languages.registerCodeLensProvider("grain", codelensProvider);
 
+    grainDocCompletionProvider = new GrainDocCompletionProvider(client);
+    languages.registerCompletionItemProvider(
+      "grain",
+      grainDocCompletionProvider,
+      "*"
+    );
+
     codelensProvider.triggerRefresh();
     client.onNotification("grainlsp/lensesLoaded", (files: Array<String>) => {
       codelensProvider.triggerRefresh();