Add "networkx.plugin_info" entry point and update docstring (networkx#6911)

* Add "networkx.plugin_info" entry point and update docstring

We use a new entry point so it can be imported really fast by not needing to import the backend.

* Fix?

* Update to better dict for info (all func info now under `'functions': {...}`)

* Add backends section to online docs for functions implemented by known backends

Also, fix a few docstring issues

* Update `.circleci/config.yml` to install `nx-cugraph` when building docs

* revert change to s_metric docstring

Author: eriknw

.circleci/config.yml

@@ -38,6 +38,10 @@ jobs:
             pip install -r requirements/extra.txt
             pip install -r requirements/example.txt
             pip install -r requirements/doc.txt
+            # Install trusted backends, but not their dependencies.
+            # We only need to use the "networkx.plugin_info" entry-point.
+            # This is the nightly wheel for nx-cugraph.
+            pip install nx-cugraph-cu11 --extra-index-url https://rapidsdev:WeArePyPI@pypi.k8s.rapids.ai/simple --no-deps
             pip list
 
       - save_cache:
@@ -49,7 +53,7 @@ jobs:
           name: Install
           command: |
             source venv/bin/activate
-            pip install -e .
+            pip install -e . --no-deps
 
       - run:
           name: Build docs

.github/workflows/deploy-docs.yml

@@ -32,6 +32,10 @@ jobs:
           pip install -r requirements/example.txt
           pip install -U -r requirements/doc.txt
           pip install .
+          # Install trusted backends, but not their dependencies.
+          # We only need to use the "networkx.plugin_info" entry-point.
+          # This is the nightly wheel for nx-cugraph.
+          pip install nx-cugraph-cu11 --extra-index-url https://rapidsdev:WeArePyPI@pypi.k8s.rapids.ai/simple --no-deps
           pip list
 
       # To set up a cross-repository deploy key:

doc/conf.py

@@ -247,3 +247,48 @@
 def setup(app):
     app.add_css_file("custom.css")
     app.add_js_file("copybutton.js")
+
+
+# Monkeypatch numpydoc to show "Backends" section
+from numpydoc.docscrape import NumpyDocString
+
+orig_setitem = NumpyDocString.__setitem__
+
+
+def new_setitem(self, key, val):
+    if key != "Backends":
+        orig_setitem(self, key, val)
+        return
+    # Update how we show backend information in the online docs.
+    # Start by creating an "admonition" section to make it stand out.
+    newval = [".. admonition:: Additional backends implement this function", ""]
+    for line in val:
+        if line and not line.startswith(" "):
+            # This line must identify a backend; let's try to add a link
+            backend, *rest = line.split(" ")
+            url = networkx.utils.backends.plugin_info.get(backend, {}).get("url")
+            if url:
+                line = f"`{backend} <{url}>`_ " + " ".join(rest)
+        newval.append(f"   {line}")
+    self._parsed_data[key] = newval
+
+
+NumpyDocString.__setitem__ = new_setitem
+
+from numpydoc.docscrape_sphinx import SphinxDocString
+
+orig_str = SphinxDocString.__str__
+
+
+def new_str(self, indent=0, func_role="obj"):
+    rv = orig_str(self, indent=indent, func_role=func_role)
+    if "Backends" in self:
+        lines = self._str_section("Backends")
+        # Remove "Backends" as a section and add a divider instead
+        lines[0] = "----"
+        lines = self._str_indent(lines, indent)
+        rv += "\n".join(lines)
+    return rv
+
+
+SphinxDocString.__str__ = new_str

networkx/utils/backends.py

@@ -96,11 +96,14 @@ class WrappedSparse:
 __all__ = ["_dispatch"]
 
 
-def _get_plugins():
+def _get_plugins(group, *, load_and_call=False):
     if sys.version_info < (3, 10):
-        items = entry_points()["networkx.plugins"]
+        eps = entry_points()
+        if group not in eps:
+            return {}
+        items = eps[group]
     else:
-        items = entry_points(group="networkx.plugins")
+        items = entry_points(group=group)
     rv = {}
     for ep in items:
         if ep.name in rv:
@@ -109,14 +112,24 @@ def _get_plugins():
                 RuntimeWarning,
                 stacklevel=2,
             )
+        elif load_and_call:
+            try:
+                rv[ep.name] = ep.load()()
+            except Exception as exc:
+                warnings.warn(
+                    f"Error encountered when loading info for plugin {ep.name}: {exc}",
+                    RuntimeWarning,
+                    stacklevel=2,
+                )
         else:
             rv[ep.name] = ep
     # nx-loopback plugin is only available when testing (added in conftest.py)
-    del rv["nx-loopback"]
+    rv.pop("nx-loopback", None)
     return rv
 
 
-plugins = _get_plugins()
+plugins = _get_plugins("networkx.plugins")
+plugin_info = _get_plugins("networkx.plugin_info", load_and_call=True)
 _registered_algorithms = {}
 
 
@@ -234,7 +247,7 @@ def __new__(
         # standard function-wrapping stuff
         # __annotations__ not used
         self.__name__ = func.__name__
-        self.__doc__ = func.__doc__
+        # self.__doc__ = func.__doc__  # __doc__ handled as cached property
         self.__defaults__ = func.__defaults__
         # We "magically" add `backend=` keyword argument to allow backend to be specified
         if func.__kwdefaults__:
@@ -246,6 +259,10 @@ def __new__(
         self.__dict__.update(func.__dict__)
         self.__wrapped__ = func
 
+        # Supplement docstring with backend info; compute and cache when needed
+        self._orig_doc = func.__doc__
+        self._cached_doc = None
+
         self.orig_func = func
         self.name = name
         self.edge_attrs = edge_attrs
@@ -306,13 +323,35 @@ def __new__(
         # Compute and cache the signature on-demand
         self._sig = None
 
+        # Load and cache backends on-demand
+        self._backends = {}
+
+        # Which backends implement this function?
+        self.backends = {
+            backend
+            for backend, info in plugin_info.items()
+            if "functions" in info and name in info["functions"]
+        }
+
         if name in _registered_algorithms:
             raise KeyError(
                 f"Algorithm already exists in dispatch registry: {name}"
             ) from None
         _registered_algorithms[name] = self
         return self
 
+    @property
+    def __doc__(self):
+        if (rv := self._cached_doc) is not None:
+            return rv
+        rv = self._cached_doc = self._make_doc()
+        return rv
+
+    @__doc__.setter
+    def __doc__(self, val):
+        self._orig_doc = val
+        self._cached_doc = None
+
     @property
     def __signature__(self):
         if self._sig is None:
@@ -462,7 +501,7 @@ def __call__(self, /, *args, backend=None, **kwargs):
                     f"{self.name}() has networkx and {plugin_name} graphs, but NetworkX is not "
                     f"configured to automatically convert graphs from networkx to {plugin_name}."
                 )
-            backend = plugins[plugin_name].load()
+            backend = self._load_backend(plugin_name)
             if hasattr(backend, self.name):
                 if "networkx" in plugin_names:
                     # We need to convert networkx graphs to backend graphs
@@ -494,9 +533,15 @@ def __call__(self, /, *args, backend=None, **kwargs):
         # Default: run with networkx on networkx inputs
         return self.orig_func(*args, **kwargs)
 
+    def _load_backend(self, plugin_name):
+        if plugin_name in self._backends:
+            return self._backends[plugin_name]
+        rv = self._backends[plugin_name] = plugins[plugin_name].load()
+        return rv
+
     def _can_backend_run(self, plugin_name, /, *args, **kwargs):
         """Can the specified backend run this algorithms with these arguments?"""
-        backend = plugins[plugin_name].load()
+        backend = self._load_backend(plugin_name)
         return hasattr(backend, self.name) and (
             not hasattr(backend, "can_run") or backend.can_run(self.name, args, kwargs)
         )
@@ -645,7 +690,7 @@ def _convert_arguments(self, plugin_name, args, kwargs):
 
         # It should be safe to assume that we either have networkx graphs or backend graphs.
         # Future work: allow conversions between backends.
-        backend = plugins[plugin_name].load()
+        backend = self._load_backend(plugin_name)
         for gname in self.graphs:
             if gname in self.list_graphs:
                 bound.arguments[gname] = [
@@ -704,7 +749,7 @@ def _convert_arguments(self, plugin_name, args, kwargs):
 
     def _convert_and_call(self, plugin_name, args, kwargs, *, fallback_to_nx=False):
         """Call this dispatchable function with a backend, converting graphs if necessary."""
-        backend = plugins[plugin_name].load()
+        backend = self._load_backend(plugin_name)
         if not self._can_backend_run(plugin_name, *args, **kwargs):
             if fallback_to_nx:
                 return self.orig_func(*args, **kwargs)
@@ -729,7 +774,7 @@ def _convert_and_call_for_tests(
         self, plugin_name, args, kwargs, *, fallback_to_nx=False
     ):
         """Call this dispatchable function with a backend; for use with testing."""
-        backend = plugins[plugin_name].load()
+        backend = self._load_backend(plugin_name)
         if not self._can_backend_run(plugin_name, *args, **kwargs):
             if fallback_to_nx:
                 return self.orig_func(*args, **kwargs)
@@ -807,6 +852,49 @@ def _convert_and_call_for_tests(
 
         return backend.convert_to_nx(result, name=self.name)
 
+    def _make_doc(self):
+        if not self.backends:
+            return self._orig_doc
+        lines = [
+            "Backends",
+            "--------",
+        ]
+        for backend in sorted(self.backends):
+            info = plugin_info[backend]
+            if "short_summary" in info:
+                lines.append(f"{backend} : {info['short_summary']}")
+            else:
+                lines.append(backend)
+            if "functions" not in info or self.name not in info["functions"]:
+                lines.append("")
+                continue
+
+            func_info = info["functions"][self.name]
+            if "extra_docstring" in func_info:
+                lines.extend(
+                    f"  {line}" if line else line
+                    for line in func_info["extra_docstring"].split("\n")
+                )
+                add_gap = True
+            else:
+                add_gap = False
+            if "extra_parameters" in func_info:
+                if add_gap:
+                    lines.append("")
+                lines.append("  Extra parameters:")
+                extra_parameters = func_info["extra_parameters"]
+                for param in sorted(extra_parameters):
+                    lines.append(f"    {param}")
+                    if desc := extra_parameters[param]:
+                        lines.append(f"      {desc}")
+                    lines.append("")
+            else:
+                lines.append("")
+
+        lines.pop()  # Remove last empty line
+        to_add = "\n    ".join(lines)
+        return f"{self._orig_doc.rstrip()}\n\n    {to_add}"
+
     def __reduce__(self):
         """Allow this object to be serialized with pickle.