Fixes error messages displayed when notebooks are started in non-jupy…

…ter based environments. Fixes #98

src/jupyter_matlab_kernel/base_kernel.py

@@ -441,7 +441,9 @@ def display_output(self, out):
             response = out["content"]
         self.send_response(self.iopub_socket, msg_type, response)
 
-    async def perform_startup_checks(self, iframe_src: str = None):
+    async def perform_startup_checks(
+        self, jupyter_base_url: str = None, matlab_proxy_base_url: str = None
+    ):
         """
         One time checks triggered during the first execution request. Displays
         login window if matlab is not licensed using matlab-proxy.
@@ -470,19 +472,32 @@ async def perform_startup_checks(self, iframe_src: str = None):
         # as src for iframe to avoid hardcoding any hostname/domain information. This is done to
         # ensure the kernel works in Jupyter deployments. VS Code however does not work the same way
         # as other browser based Jupyter clients.
-        #
-        # TODO: Find a workaround for users to be able to use our Jupyter kernel in VS Code.
         if not is_matlab_licensed:
+            if not jupyter_base_url:
+                # happens for non-jupyter environments (like VSCode), we expect licensing to
+                # be completed before hand
+                self.log.debug(
+                    "MATLAB is not licensed and is in a non-jupyter environment. licensing via other means required."
+                )
+                raise MATLABConnectionError(
+                    """
+                    Error: Cannot start MATLAB as no licensing information was found. 
+                    Resolution: Set the environment variable MLM_LICENSE_FILE to provide a network license manager, 
+                    or set MWI_USE_EXISTING_LICENSE to True if the installed MATLAB is already licensed. 
+                    See https://github.com/mathworks/matlab-proxy/blob/main/Advanced-Usage.md for more information.
+                    To use Online licensing, start a MATLAB Kernel in a Jupyter notebook and login using the web interface 
+                    shown upon execution of any code.
+                    """
+                )
             self.log.debug(
                 "MATLAB is not licensed. Displaying HTML output to enable licensing."
             )
-            self.log.debug(f"{iframe_src=}")
             self.display_output(
                 {
                     "type": "display_data",
                     "content": {
                         "data": {
-                            "text/html": f'<iframe src={iframe_src} width=700 height=600"></iframe>'
+                            "text/html": f'<iframe src={jupyter_base_url}{matlab_proxy_base_url} width=700 height=600"></iframe>'
                         },
                         "metadata": {},
                     },

src/jupyter_matlab_kernel/jsp_kernel.py

@@ -201,5 +201,4 @@ async def do_shutdown(self, restart):
 
     async def perform_startup_checks(self):
         """Overriding base function to provide a different iframe source"""
-        iframe_src: str = f'{self.jupyter_base_url + "matlab"}'
-        await super().perform_startup_checks(iframe_src)
+        await super().perform_startup_checks(self.jupyter_base_url, "matlab")

src/jupyter_matlab_kernel/mpm_kernel.py

@@ -92,10 +92,9 @@ async def do_shutdown(self, restart):
 
     async def perform_startup_checks(self):
         """Overriding base function to provide a different iframe source"""
-        iframe_src: str = (
-            f'{self.jupyter_base_url}{self.matlab_proxy_base_url.lstrip("/")}/'
+        await super().perform_startup_checks(
+            self.jupyter_base_url, f'{self.matlab_proxy_base_url.lstrip("/")}/'
         )
-        await super().perform_startup_checks(iframe_src)
 
     # Helper functions
 

tests/unit/jupyter_matlab_kernel/test_kernel.py

@@ -6,7 +6,7 @@
 from jupyter_server import serverapp
 from mocks.mock_jupyter_server import MockJupyterServerFixture
 
-from jupyter_matlab_kernel.jsp_kernel import start_matlab_proxy
+from jupyter_matlab_kernel.jsp_kernel import MATLABKernelUsingJSP, start_matlab_proxy
 from jupyter_matlab_kernel.mwi_exceptions import MATLABConnectionError
 
 
@@ -84,3 +84,32 @@ def test_start_matlab_proxy_jh_api_token(monkeypatch, MockJupyterServerFixture):
     monkeypatch.setenv("JUPYTERHUB_API_TOKEN", token)
     _, _, headers = start_matlab_proxy()
     assert headers == {"Authorization": f"token {token}"}
+
+
+async def test_matlab_not_licensed_non_jupyter(mocker):
+    """
+    Test case for MATLAB not being licensed in a non-Jupyter environment.
+
+    This test mocks a MATLABKernelUsingJSP instance to simulate a non-Jupyter
+    environment where MATLAB is not licensed. It checks if the appropriate
+    exception (MATLABConnectionError) is raised when performing startup checks.
+    """
+    # Mock the kernel's jupyter_base_url attribute to simulate a non-Jupyter environment
+    kernel = mocker.MagicMock(spec=MATLABKernelUsingJSP)
+    kernel.jupyter_base_url = None
+    kernel.startup_error = None
+    kernel.mwi_comm_helper = mocker.Mock()
+    kernel.mwi_comm_helper.fetch_matlab_proxy_status = mocker.AsyncMock(
+        return_value=(False, "down", False)
+    )
+
+    # Mock the perform_startup_checks method to actually call the implementation
+    async def mock_perform_startup_checks(*args, **kwargs):
+        return await MATLABKernelUsingJSP.perform_startup_checks(
+            kernel, *args, **kwargs
+        )
+
+    kernel.perform_startup_checks.side_effect = mock_perform_startup_checks
+
+    with pytest.raises(MATLABConnectionError):
+        await kernel.perform_startup_checks()