Add the environment scripts directory to the list of places to search for subcommands

jupyter_core/command.py

@@ -13,6 +13,7 @@
 import json
 import os
 import sys
+import sysconfig
 from subprocess import Popen
 
 try:
@@ -148,12 +149,28 @@ def _path_with_self():
     will do /path/to/jupyter-subcommand
     even if /other/jupyter-subcommand is ahead of it on PATH
     """
+    path_list = (os.environ.get('PATH') or os.defpath).split(os.pathsep)
+
+    # Insert the "scripts" directory for this Python installation
+    # This allows the "jupyter" command to be relocated, while still
+    # finding subcommands that have been installed in the default
+    # location.
+    # We put the scripts directory at the *end* of PATH, so that
+    # if the user explicitly overrides a subcommand, that override
+    # still takes effect.
+    try:
+        bindir = sysconfig.get_path('scripts')
+    except KeyError:
+        # The Python environment does not specify a "scripts" location
+        pass
+    else:
+        path_list.append(bindir)
+
     scripts = [sys.argv[0]]
     if os.path.islink(scripts[0]):
         # include realpath, if `jupyter` is a symlink
         scripts.append(os.path.realpath(scripts[0]))
 
-    path_list = (os.environ.get('PATH') or os.defpath).split(os.pathsep)
     for script in scripts:
         bindir = os.path.dirname(script)
         if (

jupyter_core/tests/test_command.py

@@ -3,6 +3,7 @@
 import json
 import os
 import sys
+import sysconfig
 from subprocess import check_output, CalledProcessError
 
 import pytest
@@ -108,17 +109,27 @@ def test_subcommand_list(tmpdir):
                 'jupyterstuff',
                 'jupyter-yo-eyropa-ganymyde-callysto'):
         b.join(cmd).write('')
+    c = tmpdir.mkdir("c")
+    for cmd in ('jupyter-baz',
+                'jupyter-bop'):
+        c.join(cmd).write('')
 
     path = os.pathsep.join(map(str, [a, b]))
+
+    def get_path(dummy):
+        return str(c)
 
-    with patch.dict('os.environ', {'PATH': path}):
-        subcommands = list_subcommands()
-        assert subcommands == [
-            'babel-fish',
-            'foo',
-            'xyz',
-            'yo-eyropa-ganymyde-callysto',
-        ]
+    with patch.object(sysconfig, 'get_path', get_path):
+        with patch.dict('os.environ', {'PATH': path}):
+            subcommands = list_subcommands()
+            assert subcommands == [
+                'babel-fish',
+                'baz',
+                'bop',
+                'foo',
+                'xyz',
+                'yo-eyropa-ganymyde-callysto',
+            ]
 
 def test_not_on_path(tmpdir):
     a = tmpdir.mkdir("a")