refactor(language-service): add missing helper method

PR angular#42559 added a reference to a helper method that was only in the 12.1.x branch.
This commit adds the helper to the 12.0.x branch.

packages/language-service/ivy/references_and_rename_utils.ts

@@ -0,0 +1,64 @@
+/**
+ * @license
+ * Copyright Google LLC 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 {absoluteFrom} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {TemplateTypeChecker} from '@angular/compiler-cli/src/ngtsc/typecheck/api';
+import {ExpressionIdentifier, hasExpressionIdentifier} from '@angular/compiler-cli/src/ngtsc/typecheck/src/comments';
+import * as ts from 'typescript';
+
+import {findTightestNode} from './ts_utils';
+import {getTemplateLocationFromShimLocation, toTextSpan} from './utils';
+
+
+/**
+ * Converts a given `ts.DocumentSpan` in a shim file to its equivalent `ts.DocumentSpan` in the
+ * template.
+ *
+ * You can optionally provide a `requiredNodeText` that ensures the equivalent template node's text
+ * matches. If it does not, this function will return `null`.
+ */
+export function convertToTemplateDocumentSpan<T extends ts.DocumentSpan>(
+    shimDocumentSpan: T, templateTypeChecker: TemplateTypeChecker, program: ts.Program,
+    requiredNodeText?: string): T|null {
+  const sf = program.getSourceFile(shimDocumentSpan.fileName);
+  if (sf === undefined) {
+    return null;
+  }
+  const tcbNode = findTightestNode(sf, shimDocumentSpan.textSpan.start);
+  if (tcbNode === undefined ||
+      hasExpressionIdentifier(sf, tcbNode, ExpressionIdentifier.EVENT_PARAMETER)) {
+    // If the reference result is the $event parameter in the subscribe/addEventListener
+    // function in the TCB, we want to filter this result out of the references. We really only
+    // want to return references to the parameter in the template itself.
+    return null;
+  }
+  // TODO(atscott): Determine how to consistently resolve paths. i.e. with the project
+  // serverHost or LSParseConfigHost in the adapter. We should have a better defined way to
+  // normalize paths.
+  const mapping = getTemplateLocationFromShimLocation(
+      templateTypeChecker, absoluteFrom(shimDocumentSpan.fileName),
+      shimDocumentSpan.textSpan.start);
+  if (mapping === null) {
+    return null;
+  }
+
+  const {span, templateUrl} = mapping;
+  if (requiredNodeText !== undefined && span.toString() !== requiredNodeText) {
+    return null;
+  }
+
+  return {
+    ...shimDocumentSpan,
+    fileName: templateUrl,
+    textSpan: toTextSpan(span),
+    // Specifically clear other text span values because we do not have enough knowledge to
+    // convert these to spans in the template.
+    contextSpan: undefined,
+    originalContextSpan: undefined,
+    originalTextSpan: undefined,
+  };
+}