Add test for #11980 (#12027)

* add test for the fix for overwrite emitting error

* cr feedback

Author: zhengbli

src/harness/unittests/tsserverProjectSystem.ts

@@ -2464,4 +2464,28 @@ namespace ts.projectSystem {
 
         });
     });
+
+    describe("No overwrite emit error", () => {
+        it("for inferred project", () => {
+            const f1 = {
+                path: "/a/b/f1.js",
+                content: "function test1() { }"
+            };
+            const host = createServerHost([f1, libFile]);
+            const session = createSession(host);
+            openFilesForSession([f1], session);
+
+            const projectService = session.getProjectService();
+            checkNumberOfProjects(projectService, { inferredProjects: 1 });
+            const projectName = projectService.inferredProjects[0].getProjectName();
+
+            const diags = session.executeCommand(<server.protocol.CompilerOptionsDiagnosticsRequest>{
+                type: "request",
+                command: server.CommandNames.CompilerOptionsDiagnosticsFull,
+                seq: 2,
+                arguments: { projectFileName: projectName }
+            }).response;
+            assert.isTrue(diags.length === 0);
+        });
+    });
 }