Do not remove inferred project immediately and try to reuse it on next file open

src/server/project.ts

@@ -591,6 +591,11 @@ namespace ts.server {
             return this.rootFiles && this.rootFiles.length > 0;
         }
 
+        /*@internal*/
+        isOrphan() {
+            return false;
+        }
+
         getRootFiles() {
             return this.rootFiles && this.rootFiles.map(info => info.fileName);
         }
@@ -1173,6 +1178,10 @@ namespace ts.server {
         /** this is canonical project root path */
         readonly projectRootPath: string | undefined;
 
+        /*@internal*/
+        /** stored only if their is no projectRootPath and this isnt single inferred project */
+        readonly canonicalCurrentDirectory: string | undefined;
+
         /*@internal*/
         constructor(
             projectService: ProjectService,
@@ -1191,6 +1200,9 @@ namespace ts.server {
                 projectService.host,
                 currentDirectory);
             this.projectRootPath = projectRootPath && projectService.toCanonicalFileName(projectRootPath);
+            if (!projectRootPath && !projectService.useSingleInferredProject) {
+                this.canonicalCurrentDirectory = projectService.toCanonicalFileName(this.currentDirectory);
+            }
             this.enableGlobalPlugins();
         }
 
@@ -1213,6 +1225,11 @@ namespace ts.server {
             }
         }
 
+        /*@internal*/
+        isOrphan() {
+            return !this.hasRoots();
+        }
+
         isProjectWithSingleRoot() {
             // - when useSingleInferredProject is not set and projectRootPath is not set,
             //   we can guarantee that this will be the only root