Construct valid signatures for remote methods

This allows client-side inspection of argument names, types and default values.

tests/test.py

@@ -9,6 +9,7 @@
 import pytest
 import requests
 import subprocess
+import inspect
 
 try:
     import test_module as tm
@@ -430,7 +431,11 @@ async def test_tuberpy_method_docstrings(tuber_call, accept_types, simple):
     """Ensure docstrings in C++ methods end up in the TuberObject's __doc__ dunder."""
 
     s = await resolve("Wrapper", accept_types, simple)
-    assert s.increment.__doc__.strip() == tm.Wrapper.increment.__doc__.strip()
+    assert s.increment.__doc__.strip() == tm.Wrapper.increment.__doc__.split("\n", 1)[-1].strip()
+
+    # check signature
+    sig = inspect.signature(s.increment)
+    assert "x" in sig.parameters
 
 
 @pytest.mark.parametrize("simple", [False])

tuber/client.py

@@ -7,6 +7,7 @@
 import textwrap
 import types
 import warnings
+import inspect
 
 from . import TuberError, TuberStateError, TuberRemoteError
 from .codecs import AcceptTypes, Codecs
@@ -60,6 +61,30 @@ def attribute_blacklisted(name):
     return False
 
 
+def tuber_wrapper(func, props):
+    """
+    Annotate the wrapper function with docstrings and signature.
+    """
+
+    # Attach docstring, if provided and valid
+    try:
+        func.__doc__ = textwrap.dedent(props.__doc__)
+    except:
+        pass
+
+    # Attach a function signature, if provided and valid
+    try:
+        # build a dummy function to parse its signature with inspect
+        code = compile(f"def sigfunc{props.__signature__}:\n pass", "sigfunc", "single")
+        exec(code, globals())
+        sig = inspect.signature(sigfunc)
+        func.__signature__ = sig
+    except:
+        pass
+
+    return func
+
+
 class SubContext:
     """A container for attributes of a top-level (registry) Context object"""
 
@@ -449,22 +474,16 @@ def tuber_resolve(self, force=False):
 
         for methname in getattr(meta, "methods", []):
             # Generate a callable prototype
-            def invoke_wrapper(name):
+            def invoke_wrapper(name, props):
                 def invoke(self, *args, **kwargs):
                     with self.tuber_context() as ctx:
                         getattr(ctx, name)(*args, **kwargs)
                         results = ctx()
                     return results[0]
 
-                return invoke
+                return tuber_wrapper(invoke, props)
 
-            invoke = invoke_wrapper(methname)
-
-            # Attach DocStrings, if provided and valid
-            try:
-                invoke.__doc__ = textwrap.dedent(methods[methname].__doc__)
-            except:
-                pass
+            invoke = invoke_wrapper(methname, methods[methname])
 
             # Associate as a class method.
             setattr(self, methname, types.MethodType(invoke, self))
@@ -530,21 +549,15 @@ async def tuber_resolve(self, force=False):
 
         for methname in getattr(meta, "methods", []):
             # Generate a callable prototype
-            def invoke_wrapper(name):
+            def invoke_wrapper(name, props):
                 async def invoke(self, *args, **kwargs):
                     async with self.tuber_context() as ctx:
                         result = getattr(ctx, name)(*args, **kwargs)
                     return await result
 
-                return invoke
+                return tuber_wrapper(invoke, props)
 
-            invoke = invoke_wrapper(methname)
-
-            # Attach DocStrings, if provided and valid
-            try:
-                invoke.__doc__ = textwrap.dedent(methods[methname].__doc__)
-            except:
-                pass
+            invoke = invoke_wrapper(methname, methods[methname])
 
             # Associate as a class method.
             setattr(self, methname, types.MethodType(invoke, self))

tuber/server.py

@@ -82,6 +82,21 @@ def describe(registry, request):
             return result_response(attr)
 
         # Complex case: return a description of a method
-        return result_response(__doc__=inspect.getdoc(attr))
+        doc = inspect.getdoc(attr)
+        sig = None
+        try:
+            sig = str(inspect.signature(attr))
+        except:
+            # pybind docstrings include a signature as the first line
+            if doc and doc.startswith(attr.__name__ + "("):
+                if "\n" in doc:
+                    sig, doc = doc.split("\n", 1)
+                    doc = doc.strip()
+                else:
+                    sig = doc
+                    doc = None
+                sig = "(" + sig.split("(", 1)[1]
+
+        return result_response(__doc__=doc, __signature__=sig)
 
     return error_response(f"Invalid request (object={objname}, method={methodname}, property={propertyname})")