Add IPython completion hook

Author: tkf

julia/magic.py

@@ -66,6 +66,37 @@ def julia(self, line, cell=None):
         return ans
 
 
+def julia_completer(self, event):
+    pos = event.line.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
+
+    julia = Julia()
+    completions = julia.eval("""
+    import REPL
+    (string, pos) -> begin
+        ret, _, should_complete =
+            REPL.completions(string, pos)
+        if should_complete
+            return map(REPL.completion_text, ret)
+        else
+            return String[]
+        end
+    end
+    """)(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
+
+
 # Add to the global docstring the class information.
 __doc__ = __doc__.format(
     JULIAMAGICS_DOC=' ' * 8 + JuliaMagics.__doc__,
@@ -80,3 +111,9 @@ def julia(self, line, cell=None):
 def load_ipython_extension(ip):
     """Load the extension in IPython."""
     ip.register_magics(JuliaMagics)
+    ip.set_hook("complete_command", julia_completer,
+                re_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.)