TS: Other review comments

Author: asgerf

javascript/extractor/lib/typescript/src/main.ts

@@ -318,7 +318,7 @@ function handleOpenProjectCommand(command: OpenProjectCommand) {
     console.warn('TypeScript: reported ' + diagnostics.length + ' semantic errors.');
     for (let diagnostic of diagnostics) {
         let text = diagnostic.messageText;
-        if (typeof text !== 'string') {
+        if (text && typeof text !== 'string') {
             text = text.messageText;
         }
         let locationStr = '';

javascript/extractor/lib/typescript/src/virtual_source_root.ts

@@ -2,7 +2,8 @@ import * as pathlib from "path";
 import * as ts from "./typescript";
 
 /**
- * Mapping from the source root to the virtual source root.
+ * Mapping from the real source root to the virtual source root,
+ * a directory whose folder structure mirrors the real source root, but with `node_modules` installed.
  */
 export class VirtualSourceRoot {
   constructor(

javascript/extractor/src/com/semmle/js/extractor/AutoBuild.java

@@ -709,12 +709,12 @@ protected DependencyInstallationResult installDependencies(Set<Path> filesToExtr
                 propsToRemove.add(packageName);
               } else {
                 // Remove file dependency on a package that don't exist in the checkout.
-                String dependecy = getChildAsString(dependencyObj, packageName);
-                if (dependecy != null && (dependecy.startsWith("file:") || dependecy.startsWith("./") || dependecy.startsWith("../"))) {
-                    if (dependecy.startsWith("file:")) {
-                      dependecy = dependecy.substring("file:".length());
+                String dependency = getChildAsString(dependencyObj, packageName);
+                if (dependency != null && (dependency.startsWith("file:") || dependency.startsWith("./") || dependency.startsWith("../"))) {
+                    if (dependency.startsWith("file:")) {
+                      dependency = dependency.substring("file:".length());
                     }
-                    Path resolvedPackage = path.getParent().resolve(dependecy + "/package.json");
+                    Path resolvedPackage = path.getParent().resolve(dependency + "/package.json");
                     if (!Files.exists(resolvedPackage)) {
                       propsToRemove.add(packageName);
                     }