spec installer to _metakernel module; run_as_main.

All classes are tightly coupled anyways and having everything together
avoids having to create a weird InstallerApp subclass on the fly.

Also drop pretense of import working in absence of IPython and Jupyter,
this was already not the case due to the import in metakernel.config.

metakernel/__init__.py

@@ -1,6 +1,5 @@
 from ._metakernel import (
-    MetaKernel, MetaKernelApp, IPythonKernel,
-    register_ipython_magics, get_metakernel)
+    MetaKernel, IPythonKernel, register_ipython_magics, get_metakernel)
 from . import pexpect
 from .replwrap import REPLWrapper, u
 from .process_metakernel import ProcessMetaKernel

metakernel/_metakernel.py

@@ -1,48 +1,43 @@
 from __future__ import print_function
 
+import base64
+import codecs
+import glob
+import imp
+import inspect
+import json
+import logging
+import os
+import pkgutil
+import subprocess
+from subprocess import CalledProcessError
 import sys
 import warnings
+
 warnings.filterwarnings('ignore', module='IPython.html.widgets')
 
 try:
-    try:
-        from ipykernel.kernelapp import IPKernelApp
-        from ipykernel.kernelbase import Kernel
-        from ipykernel.comm import CommManager
-        from IPython.paths import get_ipython_dir
-    except ImportError:
-        from IPython.kernel.zmq.kernelapp import IPKernelApp
-        from IPython.kernel.zmq.kernelbase import Kernel
-        from IPython.kernel.comm import CommManager
-        from IPython.utils.path import get_ipython_dir
-    from IPython.display import HTML
-    try:
-        from ipywidgets.widgets.widget import Widget
-    except ImportError:
-        try:
-            from IPython.html.widgets import Widget
-        except ImportError:
-            Widget = None
-    from IPython.core.formatters import IPythonDisplayFormatter
-except ImportError as e:
-    warnings.warn(
-        "Cannot load module {name} so metakernel will not be available to "
-        "IPython/jupyter.".format(name=getattr(e, 'name', '')))
-    # This module won't be useful without IPython
-    # (other parts of metakernel may be useful)
-    # but we make it loadable anyway
-    Kernel = object
-import os
-import sys
-import glob
-import base64
-import imp
-import inspect
-import logging
-import codecs
+    from IPython.paths import get_ipython_dir
+    from ipykernel.kernelapp import IPKernelApp
+    from ipykernel.kernelbase import Kernel
+    from ipykernel.comm import CommManager
+    from ipywidgets.widgets.widget import Widget
+    from traitlets.config import Application
+    _module_name = 'jupyter'
+except ImportError:
+    from IPython.utils.path import get_ipython_dir
+    from IPython.kernel.zmq.kernelapp import IPKernelApp
+    from IPython.kernel.zmq.kernelbase import Kernel
+    from IPython.kernel.comm import CommManager
+    from IPython.html.widgets import Widget
+    from IPython.config import Application
+    _module_name = 'IPython'
+
+from IPython.core.formatters import IPythonDisplayFormatter
+from IPython.display import HTML
+from IPython.utils.tempdir import TemporaryDirectory
 
 from .config import get_history_file, get_local_magics_dir
-from .utils.installer import BaseInstallerApp
 from .parser import Parser
 
 PY3 = (sys.version_info[0] >= 3)
@@ -87,6 +82,17 @@ class MetaKernel(Kernel):
     }
     meta_kernel = None
 
+    @classmethod
+    def run_as_main(cls):
+        """Launch or install a metakernel.
+
+        Modules implementing a metakernel subclass can use the following lines:
+
+            if __name__ == '__main__':
+                MetaKernelSubclass.run_as_main()
+        """
+        _MetaKernelApp.launch_instance(kernel_class=cls)
+
     def __init__(self, *args, **kwargs):
         super(MetaKernel, self).__init__(*args, **kwargs)
         if MetaKernel.meta_kernel is None:
@@ -651,16 +657,39 @@ def _get_sticky_magics(self):
         return retval
 
 
-class MetaKernelApp(IPKernelApp):
+class _MetaKernelApp(IPKernelApp):
 
     @property
     def subcommands(self):
         # Slightly awkward way to pass the actual kernel class to the install
         # subcommand.
 
-        class KernelInstallerApp(BaseInstallerApp):
+        class KernelInstallerApp(Application):
             kernel_class = self.kernel_class
 
+            def initialize(self, argv=None):
+                self.argv = argv
+
+            def start(self):
+                kernel_spec = self.kernel_class.kernel_json
+                with TemporaryDirectory() as td:
+                    dirname = os.path.join(td, kernel_spec['name'])
+                    os.mkdir(dirname)
+                    with open(os.path.join(dirname, 'kernel.json'), 'w') as f:
+                        json.dump(kernel_spec, f, sort_keys=True)
+                    filenames = ['logo-64x64.png', 'logo-32x32.png']
+                    for filename in filenames:
+                        data = pkgutil.get_data(__name__.split('.')[0],
+                                                'images/' + filename)
+                        with open(os.path.join(dirname, filename), 'wb') as f:
+                            f.write(data)
+                    try:
+                        subprocess.check_call(
+                            [sys.executable, '-m', _module_name,
+                            'kernelspec', 'install'] + self.argv + [dirname])
+                    except CalledProcessError as exc:
+                        sys.exit(exc.returncode)
+
         return {'install': (KernelInstallerApp, 'Install this kernel')}
 
 

metakernel_bash/metakernel_bash.py

@@ -60,5 +60,4 @@ def repr(self, data):
 
 
 if __name__ == '__main__':
-    from metakernel import MetaKernelApp
-    MetaKernelApp.launch_instance(kernel_class=MetaKernelBash)
+    MetaKernelBash.run_as_main()

metakernel_echo/metakernel_echo.py

@@ -41,5 +41,4 @@ def repr(self, data):
 
 
 if __name__ == '__main__':
-    from metakernel import MetaKernelApp
-    MetaKernelApp.launch_instance(kernel_class=MetaKernelEcho)
+    MetaKernelEcho.run_as_main()

metakernel_python/metakernel_python.py

@@ -69,5 +69,4 @@ def get_kernel_help_on(self, info, level=0, none_on_fail=False):
 
 
 if __name__ == '__main__':
-    from metakernel import MetaKernelApp
-    MetaKernelApp.launch_instance(kernel_class=MetaKernelPython)
+    MetaKernelPython.run_as_main()