feat: add getReferencesAtPosition to capabilities

The Angular Language Service for Ivy will have a be able to provide
references for a template location so we need to add `referencesProvider` to the capabilities.

Author: atscott

integration/lsp/viewengine_spec.ts

@@ -124,6 +124,7 @@ describe('initialization', () => {
         definitionProvider: true,
         typeDefinitionProvider: false,
         hoverProvider: true,
+        referencesProvider: false,
         workspace: {
           workspaceFolders: {
             supported: true,

server/src/session.ts

@@ -103,6 +103,7 @@ export class Session {
     conn.onDidSaveTextDocument(p => this.onDidSaveTextDocument(p));
     conn.onDefinition(p => this.onDefinition(p));
     conn.onTypeDefinition(p => this.onTypeDefinition(p));
+    conn.onReferences(p => this.onReferences(p));
     conn.onHover(p => this.onHover(p));
     conn.onCompletion(p => this.onCompletion(p));
     conn.onNotification(notification.NgccComplete, p => this.handleNgccNotification(p));
@@ -262,6 +263,7 @@ export class Session {
         },
         definitionProvider: true,
         typeDefinitionProvider: this.ivy,
+        referencesProvider: this.ivy,
         hoverProvider: true,
         workspace: {
           workspaceFolders: {supported: true},
@@ -391,6 +393,25 @@ export class Session {
     return this.tsDefinitionsToLspLocationLinks(definitions);
   }
 
+  private onReferences(params: lsp.TextDocumentPositionParams): lsp.Location[]|undefined {
+    const lsInfo = this.getLSAndScriptInfo(params.textDocument);
+    if (lsInfo === undefined) {
+      return;
+    }
+    const {languageService, scriptInfo} = lsInfo;
+    const offset = lspPositionToTsPosition(scriptInfo, params.position);
+    const references = languageService.getReferencesAtPosition(scriptInfo.fileName, offset);
+    if (references === undefined) {
+      return;
+    }
+    return references.map(ref => {
+      const scriptInfo = this.projectService.getScriptInfo(ref.fileName);
+      const range = scriptInfo ? tsTextSpanToLspRange(scriptInfo, ref.textSpan) : EMPTY_RANGE;
+      const uri = filePathToUri(ref.fileName);
+      return {uri, range};
+    });
+  }
+
   private tsDefinitionsToLspLocationLinks(
       definitions: readonly ts.DefinitionInfo[],
       originSelectionRange?: lsp.Range): lsp.LocationLink[] {