When iterating to load configured project, create copy.

Author: sheetalkamat

src/server/editorServices.ts

@@ -410,8 +410,8 @@ namespace ts.server {
     }
 
     function setProjectOptionsUsed(project: ConfiguredProject | ExternalProject) {
-        if (project.projectKind === ProjectKind.Configured) {
-            (project as ConfiguredProject).projectOptions = true;
+        if (isConfiguredProject(project)) {
+            project.projectOptions = true;
         }
     }
 
@@ -1606,7 +1606,7 @@ namespace ts.server {
                 return;
             }
 
-            const projectOptions = project.projectKind === ProjectKind.Configured ? (project as ConfiguredProject).projectOptions as ProjectOptions : undefined;
+            const projectOptions = isConfiguredProject(project) ? project.projectOptions as ProjectOptions : undefined;
             setProjectOptionsUsed(project);
             const data: ProjectInfoTelemetryEventData = {
                 projectId: this.host.createSHA256Hash(project.projectName),
@@ -2399,8 +2399,8 @@ namespace ts.server {
 
             // Add configured projects as referenced
             originalScriptInfo.containingProjects.forEach(project => {
-                if (project.projectKind === ProjectKind.Configured) {
-                    addOriginalConfiguredProject(project as ConfiguredProject);
+                if (isConfiguredProject(project)) {
+                    addOriginalConfiguredProject(project);
                 }
             });
             return originalLocation;
@@ -2536,7 +2536,9 @@ namespace ts.server {
         /*@internal*/
         loadAncestorAndReferenceConfiguredProjects(forProjects: ReadonlyMap<Project>) {
             // Load all the projects ancestor projects for seen projects
-            this.configuredProjects.forEach(project => {
+            // Because the configured projects can update in the callback, get the copy to iterate
+            const currentConfigProjects = arrayFrom(this.configuredProjects.values());
+            currentConfigProjects.forEach(project => {
                 if (project.isInitialLoadPending() &&
                     project.forEachProjectReference(returnFalse, returnFalse, path => forProjects.has(path))) {
                     // Load the project

src/server/project.ts

@@ -92,6 +92,10 @@ namespace ts.server {
         return value instanceof ScriptInfo;
     }
 
+    export function isConfiguredProject(p: Project): p is ConfiguredProject {
+        return p.projectKind === ProjectKind.Configured;
+    }
+
     export abstract class Project implements LanguageServiceHost, ModuleResolutionHost {
         private rootFiles: ScriptInfo[] = [];
         private rootFilesMap: Map<ProjectRoot> = createMap<ProjectRoot>();

src/server/session.ts

@@ -421,9 +421,8 @@ namespace ts.server {
 
         // After initial references are collected, go over every other project and see if it has a reference for the symbol definition.
         if (getDefinition) {
-            projectService.loadAncestorAndReferenceConfiguredProjects(seenProjects);
-
             const memGetDefinition = memoize(getDefinition);
+            projectService.loadAncestorAndReferenceConfiguredProjects(seenProjects);
             projectService.forEachEnabledProject(project => {
                 if (!addToSeen(seenProjects, project)) return;
                 const definition = getDefinitionInProject(memGetDefinition(), defaultProject, project);
@@ -449,7 +448,7 @@ namespace ts.server {
     }
 
     function getProjectKey(project: Project) {
-        return project.projectKind === ProjectKind.Configured ? (project as ConfiguredProject).canonicalConfigFilePath : project.projectName;
+        return isConfiguredProject(project) ? project.canonicalConfigFilePath : project.projectName;
     }
 
     function callbackProjectAndLocation<TLocation extends sourcemaps.SourceMappableLocation | undefined>(