Add IPython completion hook

Author: tkf

julia/magic.py

@@ -66,6 +66,74 @@ def julia(self, line, cell=None):
         return ans
 
 
+class JuliaCompleter(object):
+
+    """
+    Simple completion for ``%julia`` line magic.
+    """
+
+    @property
+    def jlcomplete_texts(self):
+        try:
+            return self._jlcomplete_texts
+        except AttributeError:
+            pass
+
+        julia = Julia()
+        if julia.eval('VERSION < v"0.7-"'):
+            self._jlcomplete_texts = lambda *_: []
+            return self._jlcomplete_texts
+
+        self._jlcomplete_texts = julia.eval("""
+        import REPL
+        (str, pos) -> begin
+            ret, _, should_complete =
+                REPL.completions(str, pos)
+            if should_complete
+                return map(REPL.completion_text, ret)
+            else
+                return []
+            end
+        end
+        """)
+        return self._jlcomplete_texts
+
+    def complete_command(self, _ip, event):
+        pos = event.text_until_cursor.find("%julia")
+        if pos < 0:
+            return []
+        pos += len("%julia")  # pos: beginning of Julia code
+        julia_code = event.line[pos:]
+        julia_pos = len(event.text_until_cursor) - pos
+
+        completions = self.jlcomplete_texts(julia_code, julia_pos)
+        if "." in event.symbol:
+            # When completing (say) "Base.s" we need to add the prefix "Base."
+            prefix = event.symbol.rsplit(".", 1)[0]
+            completions = [".".join((prefix, c)) for c in completions]
+        return completions
+    # See:
+    # IPython.core.completer.dispatch_custom_completer
+
+    @classmethod
+    def register(cls, ip):
+        """
+        Register `.complete_command` to IPython hook.
+
+        Parameters
+        ----------
+        ip : IPython.InteractiveShell
+            IPython `.InteractiveShell` instance passed to
+            `load_ipython_extension`.
+        """
+        ip.set_hook("complete_command", cls().complete_command,
+                    str_key="%julia")
+# See:
+# https://ipython.readthedocs.io/en/stable/api/generated/IPython.core.hooks.html
+# IPython.core.interactiveshell.init_completer
+# IPython.core.completerlib (quick_completer etc.)
+
+
 # Add to the global docstring the class information.
 __doc__ = __doc__.format(
     JULIAMAGICS_DOC=' ' * 8 + JuliaMagics.__doc__,
@@ -80,3 +148,4 @@ def julia(self, line, cell=None):
 def load_ipython_extension(ip):
     """Load the extension in IPython."""
     ip.register_magics(JuliaMagics)
+    JuliaCompleter.register(ip)

test/test_magic.py

@@ -1,6 +1,20 @@
 from IPython.testing.globalipapp import get_ipython
+import pytest
+
+from julia.core import Julia
+from julia.magic import JuliaCompleter
 import julia.magic
 
+try:
+    from types import SimpleNamespace
+except ImportError:
+    from argparse import Namespace as SimpleNamespace  # Python 2
+
+try:
+    string_types = (unicode, str)
+except NameError:
+    string_types = (str,)
+
 
 def get_julia_magics():
     return julia.magic.JuliaMagics(shell=get_ipython())
@@ -32,3 +46,50 @@ def test_failure_cell():
     jm = get_julia_magics()
     ans = jm.julia(None, '1 += 1')
     assert ans is None
+
+
+def make_event(line, text_until_cursor=None, symbol=""):
+    if text_until_cursor is None:
+        text_until_cursor = line
+    return SimpleNamespace(
+        line=line,
+        text_until_cursor=text_until_cursor,
+        symbol=symbol,
+    )
+
+
+completable_events = [
+    make_event("%julia "),
+    make_event("%julia si"),
+    make_event("%julia Base.si"),
+]
+
+uncompletable_events = [
+    make_event(""),
+    make_event("%julia si", text_until_cursor="%ju"),
+]
+
+
+def check_version():
+    julia = Julia()
+    if julia.eval('VERSION < v"0.7-"'):
+        raise pytest.skip("Completion not supported in Julia 0.6")
+
+
+@pytest.mark.parametrize("event", completable_events)
+def test_completable_events(event):
+    jc = JuliaCompleter()
+    dummy_ipython = None
+    completions = jc.complete_command(dummy_ipython, event)
+    assert isinstance(completions, list)
+    check_version()
+    assert set(map(type, completions)) <= set(string_types)
+
+
+@pytest.mark.parametrize("event", uncompletable_events)
+def test_uncompletable_events(event):
+    jc = JuliaCompleter()
+    dummy_ipython = None
+    completions = jc.complete_command(dummy_ipython, event)
+    assert isinstance(completions, list)
+    assert not completions