Allow IPython directory to be passed down to kernel selection from App

With apologies to @ivanov for creating a new Manager class.

IPython/consoleapp.py

@@ -341,6 +341,7 b' class IPythonConsoleApp(ConnectionFileMixin):'
                                 connection_file=self.connection_file,
                                 kernel_name=self.kernel_name,
                                 parent=self,
+                                ipython_dir=self.ipython_dir,
         )
         self.kernel_manager.client_factory = self.kernel_client_class
         self.kernel_manager.start_kernel(extra_arguments=self.kernel_argv)

IPython/kernel/kernelspec.py

@@ -9,8 +9,6 b' from IPython.utils.path import get_ipython_dir'
 from IPython.utils.py3compat import PY3
 from IPython.utils.traitlets import HasTraits, List, Unicode, Dict
 
-USER_KERNEL_DIR = pjoin(get_ipython_dir(), 'kernels')
-
 if os.name == 'nt':
     programdata = os.environ.get('PROGRAMDATA', None)
     if programdata:
@@ -19,12 +17,6 b" if os.name == 'nt':"
         SYSTEM_KERNEL_DIR = None
 else:
     SYSTEM_KERNEL_DIR = "/usr/share/ipython/kernels"
-
-# List of kernel directories to search. Later ones take priority over earlier.
-kernel_dirs = [
-    SYSTEM_KERNEL_DIR,
-    USER_KERNEL_DIR,
-]
     
 NATIVE_KERNEL_NAME = 'python3' if PY3 else 'python2'
 
@@ -61,53 +53,83 b' def _is_kernel_dir(path):'
     return os.path.isdir(path) and os.path.isfile(pjoin(path, 'kernel.json'))
 
 def _list_kernels_in(dir):
-    """Ensure dir exists, and return a mapping of kernel names to resource
-    directories from it.
+    """Return a mapping of kernel names to resource directories from dir.
+    
+    If dir is None or does not exist, returns an empty dict.
     """
     if dir is None or not os.path.isdir(dir):
         return {}
     return {f.lower(): pjoin(dir, f) for f in os.listdir(dir)
                         if _is_kernel_dir(pjoin(dir, f))}
 
-def _make_native_kernel_dir():
-    """Makes a kernel directory for the native kernel.
+class KernelSpecManager(HasTraits):
+    ipython_dir = Unicode()
+    def _ipython_dir_default(self):
+        return get_ipython_dir()
+
+    user_kernel_dir = Unicode()
+    def _user_kernel_dir_default(self):
+        return pjoin(self.ipython_dir, 'kernels')
     
-    The native kernel is the kernel using the same Python runtime as this
-    process. This will put its informatino in the user kernels directory.
-    """
-    path = pjoin(USER_KERNEL_DIR, NATIVE_KERNEL_NAME)
-    os.makedirs(path, mode=0o755)
-    with open(pjoin(path, 'kernel.json'), 'w') as f:
-        json.dump({'argv':[NATIVE_KERNEL_NAME, '-c',
-                           'from IPython.kernel.zmq.kernelapp import main; main()',
-                            '-f', '{connection_file}'],
-                   'display_name': 'Python 3' if PY3 else 'Python 2',
-                   'language': 'python',
-                   'codemirror_mode': {'name': 'python',
-                                       'version': sys.version_info[0]},
-                  },
-                  f, indent=1)
-    # TODO: Copy icons into directory
-    return path
+    kernel_dirs = List(
+        help="List of kernel directories to search. Later ones take priority over earlier."    
+    )    
+    def _kernel_dirs_default(self):
+        return [
+            SYSTEM_KERNEL_DIR,
+            self.user_kernel_dir,
+        ]
+
+    def _make_native_kernel_dir(self):
+        """Makes a kernel directory for the native kernel.
+        
+        The native kernel is the kernel using the same Python runtime as this
+        process. This will put its informatino in the user kernels directory.
+        """
+        path = pjoin(self.user_kernel_dir, NATIVE_KERNEL_NAME)
+        os.makedirs(path, mode=0o755)
+        with open(pjoin(path, 'kernel.json'), 'w') as f:
+            json.dump({'argv':[NATIVE_KERNEL_NAME, '-c',
+                               'from IPython.kernel.zmq.kernelapp import main; main()',
+                                '-f', '{connection_file}'],
+                       'display_name': 'Python 3' if PY3 else 'Python 2',
+                       'language': 'python',
+                       'codemirror_mode': {'name': 'python',
+                                           'version': sys.version_info[0]},
+                      },
+                      f, indent=1)
+        # TODO: Copy icons into directory
+        return path
+    
+    def find_kernel_specs(self):
+        """Returns a dict mapping kernel names to resource directories."""
+        d = {}
+        for kernel_dir in self.kernel_dirs:
+            d.update(_list_kernels_in(kernel_dir))
+        
+        if NATIVE_KERNEL_NAME not in d:
+            d[NATIVE_KERNEL_NAME] = self._make_native_kernel_dir()
+        return d
+        # TODO: Caching?
+    
+    def get_kernel_spec(self, kernel_name):
+        """Returns a :class:`KernelSpec` instance for the given kernel_name.
+        
+        Raises KeyError if the given kernel name is not found.
+        """
+        if kernel_name == 'python':
+            kernel_name = NATIVE_KERNEL_NAME
+        d = self.find_kernel_specs()
+        resource_dir = d[kernel_name.lower()]
+        return KernelSpec.from_resource_dir(resource_dir)
 
 def find_kernel_specs():
     """Returns a dict mapping kernel names to resource directories."""
-    d = {}
-    for kernel_dir in kernel_dirs:
-        d.update(_list_kernels_in(kernel_dir))
-    
-    if NATIVE_KERNEL_NAME not in d:
-        d[NATIVE_KERNEL_NAME] = _make_native_kernel_dir()
-    return d
-    # TODO: Caching?
+    return KernelSpecManager().find_kernel_specs()
 
 def get_kernel_spec(kernel_name):
     """Returns a :class:`KernelSpec` instance for the given kernel_name.
     
     Raises KeyError if the given kernel name is not found.
     """
-    if kernel_name == 'python':
-        kernel_name = NATIVE_KERNEL_NAME
-    d = find_kernel_specs()
-    resource_dir = d[kernel_name.lower()]
-    return KernelSpec.from_resource_dir(resource_dir)
  No newline at end of file
+    return KernelSpecManager().get_kernel_spec(kernel_name)
  No newline at end of file

IPython/kernel/manager.py

@@ -19,6 +19,7 b' import zmq'
 from IPython.config.configurable import LoggingConfigurable
 from IPython.utils.importstring import import_item
 from IPython.utils.localinterfaces import is_local_ip, local_ips
+from IPython.utils.path import get_ipython_dir
 from IPython.utils.traitlets import (
     Any, Instance, Unicode, List, Bool, Type, DottedObjectName
 )
@@ -60,15 +61,20 b' class KernelManager(LoggingConfigurable, ConnectionFileMixin):'
     # generally a Popen instance
     kernel = Any()
     
+    kernel_spec_manager = Instance(kernelspec.KernelSpecManager)
+    
+    def _kernel_spec_manager_default(self):
+        return kernelspec.KernelSpecManager(ipython_dir=self.ipython_dir)
+    
     kernel_name = Unicode('python')
     
     kernel_spec = Instance(kernelspec.KernelSpec)
     
     def _kernel_spec_default(self):
-        return kernelspec.get_kernel_spec(self.kernel_name)
+        return self.kernel_spec_manager.get_kernel_spec(self.kernel_name)
     
     def _kernel_name_changed(self, name, old, new):
-        self.kernel_spec = kernelspec.get_kernel_spec(new)
+        self.kernel_spec = self.kernel_spec_manager.get_kernel_spec(new)
         self.ipython_kernel = new in {'python', 'python2', 'python3'}
 
     kernel_cmd = List(Unicode, config=True,
@@ -91,6 +97,10 b' class KernelManager(LoggingConfigurable, ConnectionFileMixin):'
         self.ipython_kernel = False
 
     ipython_kernel = Bool(True)
+    
+    ipython_dir = Unicode()
+    def _ipython_dir_default(self):
+        return get_ipython_dir()
 
     # Protected traits
     _launch_args = Any()