Add test to verify the document is released from source file when info is orphan

src/harness/unittests/tsserverProjectSystem.ts

@@ -8383,4 +8383,47 @@ new C();`
             verifyCompletionListWithNewFileInSubFolder(TestFSWithWatch.Tsc_WatchDirectory.DynamicPolling);
         });
     });
+
+    describe("document registry in project service", () => {
+        it("Caches the source file if script info is orphan", () => {
+            const projectRootPath = "/user/username/projects/project";
+            const importModuleContent = `import {a} from "./module1"`;
+            const file: File = {
+                path: `${projectRootPath}/index.ts`,
+                content: importModuleContent
+            };
+            const moduleFile: File = {
+                path: `${projectRootPath}/module1.d.ts`,
+                content: "export const a: number;"
+            };
+            const configFile: File = {
+                path: `${projectRootPath}/tsconfig.json`,
+                content: JSON.stringify({ files: ["index.ts"] })
+            };
+            const host = createServerHost([file, moduleFile, libFile, configFile]);
+            const service = createProjectService(host);
+            service.openClientFile(file.path);
+            const project = service.configuredProjects.get(configFile.path);
+            checkProject(/*moduleIsOrphan*/ false);
+
+            // edit file
+            const info = service.getScriptInfo(file.path);
+            service.applyChangesToFile(info, [{ span: { start: 0, length: importModuleContent.length }, newText: "" }]);
+            checkProject(/*moduleIsOrphan*/ true);
+
+            // write content back
+            service.applyChangesToFile(info, [{ span: { start: 0, length: 0 }, newText: importModuleContent }]);
+            checkProject(/*moduleIsOrphan*/ false);
+
+            function checkProject(moduleIsOrphan: boolean) {
+                // Update the project
+                project.getLanguageService();
+                checkProjectActualFiles(project, [file.path, libFile.path, configFile.path, ...(moduleIsOrphan ? [] : [moduleFile.path])]);
+                const moduleInfo = service.getScriptInfo(moduleFile.path);
+                assert.isDefined(moduleInfo);
+                assert.equal(moduleInfo.isOrphan(), moduleIsOrphan);
+                assert.equal(service.documentRegistry.hasDocument(moduleInfo.path), !moduleIsOrphan);
+            }
+        });
+    });
 }

src/server/editorServices.ts

@@ -339,7 +339,8 @@ namespace ts.server {
         /*@internal*/
         readonly typingsCache: TypingsCache;
 
-        private readonly documentRegistry: DocumentRegistry;
+        /*@internal*/
+        readonly documentRegistry: DocumentRegistry;
 
         /**
          * Container of all known scripts

src/services/documentRegistry.ts

@@ -87,6 +87,9 @@ namespace ts {
 
         releaseDocumentWithKey(path: Path, key: DocumentRegistryBucketKey): void;
 
+        /*@internal*/
+        hasDocument(path: Path): boolean;
+
         reportStats(): string;
     }
 
@@ -225,6 +228,10 @@ namespace ts {
             }
         }
 
+        function hasDocument(path: Path) {
+            return !!forEachEntry(buckets, bucket => bucket.has(path));
+        }
+
         return {
             acquireDocument,
             acquireDocumentWithKey,
@@ -232,6 +239,7 @@ namespace ts {
             updateDocumentWithKey,
             releaseDocument,
             releaseDocumentWithKey,
+            hasDocument,
             reportStats,
             getKeyForCompilationSettings
         };

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -8124,7 +8124,6 @@ declare namespace ts.server {
         syntaxOnly?: boolean;
     }
     class ProjectService {
-        private readonly documentRegistry;
         /**
          * Container of all known scripts
          */