Don't crash when a JS file appears in an inferred context

src/harness/unittests/tsserverProjectSystem.ts

@@ -1774,6 +1774,28 @@ namespace ts.projectSystem {
             checkProjectActualFiles(projectService.externalProjects[0], [file1.path, file2.path, file3.path]);
         });
 
+        it("regression test for crash in acquireOrUpdateDocument", () => {
+            const tsFile = {
+                fileName: "/a/b/file1.ts",
+                path: "/a/b/file1.ts",
+                content: ""
+            };
+            const jsFile = {
+                path: "/a/b/file1.js",
+                content: "var x = 10;",
+                fileName: "/a/b/file1.js",
+                scriptKind: "JS" as "JS"
+            };
+
+            const host = createServerHost([]);
+            const projectService = createProjectService(host);
+            projectService.applyChangesInOpenFiles([tsFile], [], []);
+            const projs = projectService.synchronizeProjectList([]);
+            projectService.findProject(projs[0].info.projectName).getLanguageService().getNavigationBarItems(tsFile.fileName);
+            projectService.synchronizeProjectList([projs[0].info]);
+            projectService.applyChangesInOpenFiles([jsFile], [], []);
+        });
+
         it("config file is deleted", () => {
             const file1 = {
                 path: "/a/b/f1.ts",
@@ -1874,7 +1896,7 @@ namespace ts.projectSystem {
 
             // Open HTML file
             projectService.applyChangesInOpenFiles(
-                /*openFiles*/ [{ fileName: file2.path, hasMixedContent: true, scriptKind: ScriptKind.JS, content: `var hello = "hello";` }],
+                /*openFiles*/[{ fileName: file2.path, hasMixedContent: true, scriptKind: ScriptKind.JS, content: `var hello = "hello";` }],
                 /*changedFiles*/ undefined,
                 /*closedFiles*/ undefined);
 
@@ -1891,7 +1913,7 @@ namespace ts.projectSystem {
             projectService.applyChangesInOpenFiles(
                 /*openFiles*/ undefined,
                 /*changedFiles*/ undefined,
-                /*closedFiles*/ [file2.path]);
+                /*closedFiles*/[file2.path]);
 
             // HTML file is still included in project
             checkNumberOfProjects(projectService, { configuredProjects: 1 });
@@ -3322,7 +3344,7 @@ namespace ts.projectSystem {
             const error1Result = <protocol.Diagnostic[]>session.executeCommand(dTsFile1GetErrRequest).response;
             assert.isTrue(error1Result.length === 0);
 
-             const dTsFile2GetErrRequest = makeSessionRequest<protocol.SemanticDiagnosticsSyncRequestArgs>(
+            const dTsFile2GetErrRequest = makeSessionRequest<protocol.SemanticDiagnosticsSyncRequestArgs>(
                 CommandNames.SemanticDiagnosticsSync,
                 { file: dTsFile2.path }
             );

src/server/editorServices.ts

@@ -1648,7 +1648,7 @@ namespace ts.server {
             if (openFiles) {
                 for (const file of openFiles) {
                     const scriptInfo = this.getScriptInfo(file.fileName);
-                    Debug.assert(!scriptInfo || !scriptInfo.isScriptOpen());
+                    Debug.assert(!scriptInfo || !scriptInfo.isScriptOpen(), "Script should not exist and not be open already");
                     const normalizedPath = scriptInfo ? scriptInfo.fileName : toNormalizedPath(file.fileName);
                     this.openClientFileWithNormalizedPath(normalizedPath, file.content, tryConvertScriptKindName(file.scriptKind), file.hasMixedContent);
                 }

src/services/documentRegistry.ts

@@ -173,14 +173,12 @@ namespace ts {
             const bucket = getBucketForCompilationSettings(key, /*createIfMissing*/ true);
             let entry = bucket.get(path);
             if (!entry) {
-                Debug.assert(acquiring, "How could we be trying to update a document that the registry doesn't have?");
-
                 // Have never seen this file with these settings.  Create a new source file for it.
                 const sourceFile = createLanguageServiceSourceFile(fileName, scriptSnapshot, compilationSettings.target, version, /*setNodeParents*/ false, scriptKind);
 
                 entry = {
                     sourceFile,
-                    languageServiceRefCount: 0,
+                    languageServiceRefCount: 1,
                     owners: []
                 };
                 bucket.set(path, entry);
@@ -193,15 +191,15 @@ namespace ts {
                     entry.sourceFile = updateLanguageServiceSourceFile(entry.sourceFile, scriptSnapshot, version,
                         scriptSnapshot.getChangeRange(entry.sourceFile.scriptSnapshot));
                 }
-            }
 
-            // If we're acquiring, then this is the first time this LS is asking for this document.
-            // Increase our ref count so we know there's another LS using the document.  If we're
-            // not acquiring, then that means the LS is 'updating' the file instead, and that means
-            // it has already acquired the document previously.  As such, we do not need to increase
-            // the ref count.
-            if (acquiring) {
-                entry.languageServiceRefCount++;
+                // If we're acquiring, then this is the first time this LS is asking for this document.
+                // Increase our ref count so we know there's another LS using the document.  If we're
+                // not acquiring, then that means the LS is 'updating' the file instead, and that means
+                // it has already acquired the document previously.  As such, we do not need to increase
+                // the ref count.
+                if (acquiring) {
+                    entry.languageServiceRefCount++;
+                }
             }
 
             return entry.sourceFile;