Call Julia(init_julia=False) automatically

Author: tkf

src/ipython_jl/ipyext.py

@@ -1,3 +1,10 @@
+from __future__ import print_function
+
+from contextlib import contextmanager
+import os
+import sys
+import traceback
+
 from .core import get_cached_api
 
 try:
@@ -53,6 +60,43 @@ def julia_inputhook(context):
         jl_sleep(0.05)
 
 
+@contextmanager
+def init_julia_message_on_failure():
+    try:
+        yield
+    except Exception:
+        traceback.print_exc()
+        print(file=sys.stderr)
+        print("Executing `julia.Julia(init_julia=False)` failed.",
+              "It is safe to ignore this exception unless you are",
+              "going to use PyJulia.",
+              file=sys.stderr)
+        print("To suppress automatic PyJulia initialization,",
+              "set environment variable `IPYTHON_JL_SETUP_PYJULIA`",
+              'to "no".',
+              file=sys.stderr)
+
+
+def maybe_load_pyjulia():
+    """
+    Execute ``julia.Julia(init_julia=False)`` if appropriate.
+
+    It is useful since it skips initialization when creating the
+    global "cached" API.  This makes PyJuli initialization slightly
+    faster and also makes sure to not load incompatible `libjulia`
+    when the name of the julia command of this process is not `julia`.
+    """
+    if (os.environ.get("IPYTHON_JL_SETUP_PYJULIA", "yes").lower()
+            in ("yes", "t", "true")):
+        try:
+            from julia import Julia
+        except ImportError:
+            pass
+        else:
+            with init_julia_message_on_failure():
+                Julia(init_julia=False)
+
+
 def load_ipython_extension(ip):
     global _unregister_key_bindings
     _unregister_key_bindings = register_key_bindings(ip)
@@ -62,6 +106,8 @@ def load_ipython_extension(ip):
     if not ip.active_eventloop:
         ip.enable_gui("julia")
 
+    maybe_load_pyjulia()
+
     ip.set_hook("complete_command", _julia_completer,
                 re_key=r""".*\bMain\.eval\(["']""")
 # See:

src/ipython_jl/tests/test_ipyext.py

@@ -1,6 +1,6 @@
 import pytest
 
-from ..ipyext import julia_completer
+from ..ipyext import julia_completer, init_julia_message_on_failure
 
 try:
     from types import SimpleNamespace
@@ -60,3 +60,18 @@ def test_uncompletable_events(julia, event):
 
 def test_inputhook_registration(ipy_with_magic):
     assert ipy_with_magic.active_eventloop == "julia"
+
+
+def test_init_julia_message_on_failure__with_exception(capsys):
+    msg = "exception must be captured"
+    with init_julia_message_on_failure():
+        raise Exception(msg)
+    captured = capsys.readouterr()
+    assert not captured.out
+    assert msg in captured.err
+    assert "It is safe to ignore this exception" in captured.err
+
+
+def test_init_julia_message_on_failure__no_exception():
+    with init_julia_message_on_failure():
+        pass