shimming.md

Transitioning from Jupyter Notebook to Jupyter Server.

A story about configuration

Trait path

Steps to handling traits during a "Transition and Deprecation Period".

1. If the argument is prefixed with ServerApp, pass this trait to ServerApp.
2. If the argument is prefixed with NotebookApp,
   • If the argument is a trait of NotebookApp and ServerApp:
     1. Raise a warning—for the extension developers—that there's redundant traits.
     2. Pass trait to NotebookApp.
   • If the argument is a trait of just ServerApp only (i.e. the trait moved from NotebookApp to ServerApp):
     1. Raise a "DeprecationWarning: this trait has moved" for the user.
     2. Migrate/write the trait to a new config file if it came from a config file.
     3. Pass trait to ServerApp.
   • If the argument is a trait of NotebookApp only, pass trait to NotebookApp.
   • If the argument is not found in any object, raise a "Trait not found." error.
3. If the argument is prefixed with ExtensionApp:
   • If the argument is a trait of ExtensionApp and either NotebookApp or ServerApp,
     1. Raise a warning—for the extension developers—that there's redundant traits.
     2. Pass trait to Step 2 above.
   • If the argument is not a trait of ExtensionApp, but is a trait of either NotebookApp or ServerApp (i.e. the trait moved from ExtensionApp to NotebookApp/ServerApp):
     1. Raise a "DeprecationWarning: this trait has moved" for the user.
     2. Migrate/write the trait to a new config file if it came from a config file.
     3. Pass trait to Step 2 above.
   • If the argument is not a trait of ExtensionApp and not a trait of either NotebookApp or ServerApp, raise a "Trait not found." error.

How JupyterApp's Parse Config.

Valid for traitlets 4.3.x

Here's a snapshot of how JupyterApp's are initialized. The order of operations we care about goes as follows:

1. argv is parsed.
2. parse_command_line() is called and argv is passed to this method.
3. load_config_file() is called to load traits from various files.

# Pulled from Traitlets 4.3.2

    @catch_config_error
    def initialize(self, argv=None):
        # don't hook up crash handler before parsing command-line
        if argv is None:
            argv = sys.argv[1:]
        if argv:
            subc = self._find_subcommand(argv[0])
            if subc:
                self.argv = argv
                self.subcommand = subc
                return
        self.parse_command_line(argv)
        cl_config = deepcopy(self.config)
        if self._dispatching:
            return
        self.migrate_config()
        self.load_config_file()
        # enforce cl-opts override configfile opts:
        self.update_config(cl_config)
        if allow_insecure_writes:
            issue_insecure_write_warning()

Where do we add the steps above?