feat(language-server): understand the api binding attribute

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/language-server/src/html-service.ts

@@ -5,6 +5,7 @@
 // cleanly, so import it explicitly.
 import {
   getLanguageService,
+  newHTMLDataProvider,
   TextDocument as HtmlTextDocument,
 } from "vscode-html-languageservice/lib/esm/htmlLanguageService.js";
 import { isInsideHtml, virtualHtmlDocument } from "./html-regions.ts";
@@ -19,7 +20,21 @@ export interface HtmlCompletionItem {
   insertText?: string;
 }
 
-const service = getLanguageService();
+/**
+ * `api="<name>"` / `api="<name>()"` / `api="<name>({ field: value })"` is a
+ * WRNexus data-api binding, not arbitrary markup — declaring it here keeps
+ * the HTML service from treating it as an unrecognized attribute on any
+ * element, without inventing an attribute-value grammar the library would
+ * try to spell-check as prose.
+ */
+const wrnexusDataProvider = newHTMLDataProvider("wrnexus", {
+  version: 1,
+  globalAttributes: [
+    { name: "api", description: "Binds this element to a declared `apis { }` entry." },
+  ],
+});
+
+const service = getLanguageService({ customDataProviders: [wrnexusDataProvider] });
 
 /** The virtual document as the HTML service's own document type. */
 function htmlDocument(document: TextDocument) {
@@ -41,8 +56,24 @@ function markdown(value: unknown): string | undefined {
  * Every item carries the `1` sortText prefix so the server can rank WRNexus
  * entries above these without filtering either list.
  */
+/**
+ * True when `offset` sits inside the quotes of an `api="…"` attribute value.
+ *
+ * The value is a call expression (`name`, `name()`, `name({ field: value })`),
+ * not prose, so completion there is routed to `apiCallCompletions` instead of
+ * the HTML service's own (text-oriented) attribute-value completion.
+ */
+export function isApiAttributeValuePosition(document: TextDocument, position: Position): boolean {
+  const offset = offsetAt(document.text, position);
+  if (!isInsideHtml(document, offset)) return false;
+
+  const before = document.text.slice(0, offset);
+  return /\bapi\s*=\s*(["'])(?:(?!\1)[^\n])*$/.test(before);
+}
+
 export function htmlCompletions(document: TextDocument, position: Position): HtmlCompletionItem[] {
   if (!isInsideHtml(document, offsetAt(document.text, position))) return [];
+  if (isApiAttributeValuePosition(document, position)) return [];
 
   const virtual = htmlDocument(document);
   const parsed = service.parseHTMLDocument(virtual);