Deprecate %U username substitution

docs/source/api/spawner.rst

@@ -13,6 +13,6 @@ Module: :mod:`jupyterhub.spawner`
 ----------------
 
 .. autoclass:: Spawner
-    :members: options_from_form, poll, start, stop, get_args, get_env, get_state
+    :members: options_from_form, poll, start, stop, get_args, get_env, get_state, template_namespace, format_string
 
 .. autoclass:: LocalProcessSpawner

jupyterhub/spawner.py

@@ -21,6 +21,7 @@
 from traitlets.config import LoggingConfigurable
 from traitlets import (
     Any, Bool, Dict, Instance, Integer, Float, List, Unicode,
+    validate,
 )
 
 from .traitlets import Command
@@ -147,7 +148,7 @@ def options_from_form(self, form_data):
         help="""The notebook directory for the single-user server
 
         `~` will be expanded to the user's home directory
-        `%U` will be expanded to the user's username
+        `{username}` will be expanded to the user's username
         """
     ).tag(config=True)
 
@@ -158,10 +159,22 @@ def options_from_form(self, form_data):
         full filesystem traversal, while preserving user's homedir as
         landing page for notebook
 
-        `%U` will be expanded to the user's username
+        `{username}` will be expanded to the user's username
         """
     ).tag(config=True)
 
+    @validate('notebook_dir', 'default_url')
+    def _deprecate_percent_u(self, proposal):
+        print(proposal)
+        v = proposal['value']
+        if '%U' in v:
+            self.log.warn("%%U for username in %s is deprecated in JupyterHub 0.7, use {username}",
+                proposal['trait'].name,
+            )
+            v = v.replace('%U', '{username}')
+            self.log.warn("Converting %r to %r", proposal['value'], v)
+        return v
+
     disable_user_config = Bool(False,
         help="""Disable per-user configuration of single-user servers.
 
@@ -243,7 +256,45 @@ def get_env(self):
 
         env['JPY_API_TOKEN'] = self.api_token
         return env
-
+
+    def template_namespace(self):
+        """Return the template namespace for format-string formatting.
+
+        Currently used on default_url and notebook_dir.
+
+        Subclasses may add items to the available namespace.
+
+        The default implementation includes::
+
+            {
+              'username': user.name,
+              'base_url': users_base_url,
+            }
+
+        Returns:
+
+            ns (dict): namespace for string formatting.
+        """
+        d = {'username': self.user.name}
+        if self.user.server:
+            d['base_url'] = self.user.server.base_url
+        return d
+
+    def format_string(self, s):
+        """Render a Python format string
+
+        Uses :meth:`Spawner.template_namespace` to populate format namespace.
+
+        Args:
+
+            s (str): Python format-string to be formatted.
+
+        Returns:
+
+            str: Formatted string, rendered
+        """
+        return s.format(**self.template_namespace())
+
     def get_args(self):
         """Return the arguments to be passed after self.cmd"""
         args = [
@@ -264,11 +315,11 @@ def get_args(self):
             args.append('--port=%i' % self.user.server.port)
 
         if self.notebook_dir:
-            self.notebook_dir = self.notebook_dir.replace("%U",self.user.name)
-            args.append('--notebook-dir=%s' % self.notebook_dir)
+            notebook_dir = self.format_string(self.notebook_dir)
+            args.append('--notebook-dir=%s' % notebook_dir)
         if self.default_url:
-            self.default_url = self.default_url.replace("%U",self.user.name)
-            args.append('--NotebookApp.default_url=%s' % self.default_url)
+            default_url = self.format_string(self.default_url)
+            args.append('--NotebookApp.default_url=%s' % default_url)
 
         if self.debug:
             args.append('--debug')

jupyterhub/tests/test_spawner.py

@@ -41,6 +41,8 @@ def new_spawner(db, **kwargs):
     kwargs.setdefault('cmd', [sys.executable, '-c', _echo_sleep])
     kwargs.setdefault('user', db.query(orm.User).first())
     kwargs.setdefault('hub', db.query(orm.Hub).first())
+    kwargs.setdefault('notebook_dir', os.getcwd())
+    kwargs.setdefault('default_url', '/user/{username}/lab')
     kwargs.setdefault('INTERRUPT_TIMEOUT', 1)
     kwargs.setdefault('TERM_TIMEOUT', 1)
     kwargs.setdefault('KILL_TIMEOUT', 1)
@@ -128,6 +130,7 @@ def test_stop_spawner_stop_now(db, io_loop):
     status = io_loop.run_sync(spawner.poll)
     assert status == -signal.SIGTERM
 
+
 def test_spawner_poll(db, io_loop):
     first_spawner = new_spawner(db)
     user = first_spawner.user
@@ -160,6 +163,7 @@ def test_spawner_poll(db, io_loop):
     status = io_loop.run_sync(spawner.poll)
     assert status is not None
 
+
 def test_setcwd():
     cwd = os.getcwd()
     with tempfile.TemporaryDirectory() as td:
@@ -178,3 +182,13 @@ def raiser(path):
         spawnermod._try_setcwd(cwd)
         assert os.getcwd().startswith(temp_root)
     os.chdir(cwd)
+
+
+def test_string_formatting(db):
+    s = new_spawner(db, notebook_dir='user/%U/', default_url='/base/{username}')
+    name = s.user.name
+    assert s.notebook_dir == 'user/{username}/'
+    assert s.default_url == '/base/{username}'
+    assert s.format_string(s.notebook_dir) == 'user/%s/' % name
+    assert s.format_string(s.default_url) == '/base/%s' % name
+