feat(language-service): add services to support editors (#12987)

modules/@angular/language-service/src/hover.ts

@@ -0,0 +1,28 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {TemplateInfo} from './common';
+import {locateSymbol} from './locate_symbol';
+import {Hover, HoverTextSection, Symbol} from './types';
+
+export function getHover(info: TemplateInfo): Hover {
+  const result = locateSymbol(info);
+  if (result) {
+    return {text: hoverTextOf(result.symbol), span: result.span};
+  }
+}
+
+function hoverTextOf(symbol: Symbol): HoverTextSection[] {
+  const result: HoverTextSection[] =
+      [{text: symbol.kind}, {text: ' '}, {text: symbol.name, language: symbol.language}];
+  const container = symbol.container;
+  if (container) {
+    result.push({text: ' of '}, {text: container.name, language: container.language});
+  }
+  return result;
+}