Turn back into binary agent or userdata if dict

To properly assemble a multipart data we need raw bytes
If both are bytes just pass them as they are.
If either user or agent data is dict we need to assemble back
the raw binary data (including the content type stenza)

(Maybe we should reload the files in their binary form instead?)

cloudinit/sources/DataSourceWSL.py

@@ -320,13 +320,24 @@ def _get_data(self) -> bool:
         if not any([user_data, agent_data]):
             return False
 
-        # If we cannot reliably model data files as dicts, then we cannot merge
-        # ourselves, so we can pass the data in ascending order as a list for
-        # cloud-init to handle internally
-        if isinstance(agent_data, bytes) or isinstance(user_data, bytes):
+        # If we cannot reliably model both data files as dicts, then we cannot
+        # merge them ourselves, so we can pass the data in ascending order as
+        # a list of binary contents for cloud-init to handle internally
+        if isinstance(agent_data, bytes) and isinstance(user_data, bytes):
             self.userdata_raw = cast(Any, [user_data, agent_data])
             return True
 
+        if isinstance(user_data, bytes):
+            self.userdata_raw = cast(
+                Any, [user_data, "#cloud-config\n%s" % yaml.dump(agent_data)]
+            )
+            return True
+
+        if isinstance(agent_data, bytes):
+            self.userdata_raw = cast(
+                Any, ["#cloud-config\n%s" % yaml.dump(user_data), agent_data]
+            )
+            return True
         # We only care about overriding modules entirely, so we can just
         # iterate over the top level keys and write over them if the agent
         # provides them instead.

tests/unittests/sources/test_wsl.py

@@ -625,6 +625,67 @@ def test_landscape_empty_data(self, m_get_linux_dist, tmpdir, paths):
             "agent_test" in userdata and "agent_token" in userdata
         ), "Agent data should be present"
 
+    @mock.patch("cloudinit.util.get_linux_distro")
+    def test_landscape_shell_script(self, m_get_linux_dist, tmpdir, paths):
+        """Asserts that Pro for WSL and Landscape goes multipart"""
+
+        m_get_linux_dist.return_value = SAMPLE_LINUX_DISTRO
+
+        ubuntu_pro_tmp = tmpdir.join(".ubuntupro", ".cloud-init")
+        os.makedirs(ubuntu_pro_tmp, exist_ok=True)
+
+        agent_file = ubuntu_pro_tmp.join("agent.yaml")
+        agent_file.write(
+            """#cloud-config
+landscape:
+    host:
+        url: hosted.com:6554
+    client:
+        account_name: agent_test
+        url: https://hosted.com/message-system
+        ping_url: https://hosted.com/ping
+        ssl_public_key: C:\\Users\\User\\server.pem
+        tags: wsl
+ubuntu_pro:
+    token: agent_token"""
+        )
+
+        COMMAND = "echo Hello cloud-init on WSL!"
+        landscape_file = ubuntu_pro_tmp.join("%s.user-data" % INSTANCE_NAME)
+        landscape_file.write(f"#!/bin/sh\n{COMMAND}\n")
+
+        # Run the datasource
+        ds = wsl.DataSourceWSL(
+            sys_cfg=SAMPLE_CFG,
+            distro=_get_distro("ubuntu"),
+            paths=paths,
+        )
+
+        # Assert Landscape and Agent combine, with Agent taking precedence
+        assert ds.get_data() is True
+        ud = ds.get_userdata()
+
+        assert ud is not None
+        userdata = cast(
+            str,
+            join_payloads_from_content_type(
+                cast(MIMEMultipart, ud), "text/cloud-config"
+            ),
+        )
+
+        assert (
+            "agent_test" in userdata and "agent_token" in userdata
+        ), "Agent data should be present"
+
+        shell_script = cast(
+            str,
+            join_payloads_from_content_type(
+                cast(MIMEMultipart, ud), "text/x-shellscript"
+            ),
+        )
+
+        assert COMMAND in shell_script
+
     @mock.patch("cloudinit.util.get_linux_distro")
     def test_with_landscape_no_tags(self, m_get_linux_dist, tmpdir, paths):
         """Validates the Pro For WSL default Landscape tags are applied"""