fix rendering of multiple parts in sphinx

Author: mathiasertl

docs/reference.rst

@@ -83,7 +83,7 @@ The first part will just create a file (and error out if it wasn't created).
 
 .. structured-tutorial-part::
 
-The second part will test if ``ncat`` is installed and invoke it in a subshell:
+The second part will test if ``ncat`` is installed and call it after a three-second delay:
 
 .. structured-tutorial-part::
 

docs/tutorials/test-command/tutorial.yaml

@@ -20,7 +20,7 @@ parts:
               port: 1234
               delay: 2  # wait for three seconds before even trying
               retry: 3  # retry up to three times (command will be run up to four times)
-              backoff_factor: 1  # wait for 0, 5, 10 and 20 seconds between retries
+              backoff_factor: 1  # wait for 1, 2 and 4 seconds before retries
           cleanup:
             - command: pkill sleep
             - command: pkill ncat

structured_tutorials/sphinx/utils.py

@@ -87,4 +87,5 @@ def render_part(self) -> str:
             text = self.render_code_block(part)
         else:  # pragma: no cover
             raise ValueError("unsupported part type.")
+        self.next_part += 1
         return text