feat(api): support tab completion for backends

ibis/__init__.py

@@ -1,4 +1,7 @@
 """Initialize Ibis module."""
+from __future__ import annotations
+
+import importlib.metadata as _importlib_metadata
 
 # Converting an Ibis schema to a pandas DataFrame requires registering
 # some type conversions that are currently registered in the pandas backend
@@ -12,18 +15,29 @@
 from ibis.expr import api
 from ibis.expr.api import *  # noqa: F401,F403
 
-try:
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    # TODO: remove this when Python 3.9 support is dropped
-    import importlib_metadata
-
-__all__ = ['api', 'ir', 'util', 'IbisError', 'options']
+__all__ = ['api', 'ir', 'util', 'BaseBackend', 'IbisError', 'options']
 __all__ += api.__all__
 
 __version__ = "3.0.2"
 
 
+def _get_backend_entrypoints() -> list[_importlib_metadata.EntryPoint]:
+    """Get the list of installed `ibis.backend` entrypoints"""
+    import sys
+
+    if sys.version_info < (3, 10):
+        return list(_importlib_metadata.entry_points()['ibis.backends'])
+    else:
+        return list(_importlib_metadata.entry_points(group="ibis.backends"))
+
+
+def __dir__() -> list[str]:
+    """Adds tab completion for ibis backends to the top-level module"""
+    out = set(__all__)
+    out.update(ep.name for ep in _get_backend_entrypoints())
+    return sorted(out)
+
+
 def __getattr__(name: str) -> BaseBackend:
     """Load backends in a lazy way with `ibis.<backend-name>`.
 
@@ -39,11 +53,7 @@ def __getattr__(name: str) -> BaseBackend:
     the `ibis.backends` entrypoints. If successful, the `ibis.sqlite`
     attribute is "cached", so this function is only called the first time.
     """
-    entry_points = {
-        entry_point
-        for entry_point in importlib_metadata.entry_points()["ibis.backends"]
-        if name == entry_point.name
-    }
+    entry_points = {ep for ep in _get_backend_entrypoints() if ep.name == name}
 
     if not entry_points:
         raise AttributeError(

ibis/backends/conftest.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-import importlib
+import importlib.metadata
 import os
 import platform
 from functools import lru_cache
@@ -19,12 +19,6 @@
 import ibis
 import ibis.util as util
 
-try:
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    import importlib_metadata
-
-
 TEST_TABLES = {
     "functional_alltypes": ibis.schema(
         {
@@ -236,10 +230,15 @@ def _get_backend_names() -> frozenset[str]:
     If a `set` is used, then any in-place modifications to the set
     are visible to every caller of this function.
     """
-    return frozenset(
-        entry_point.name
-        for entry_point in importlib_metadata.entry_points()["ibis.backends"]
-    )
+    import sys
+
+    if sys.version_info < (3, 10):
+        entrypoints = list(importlib.metadata.entry_points()['ibis.backends'])
+    else:
+        entrypoints = list(
+            importlib.metadata.entry_points(group="ibis.backends")
+        )
+    return frozenset(ep.name for ep in entrypoints)
 
 
 def _get_backend_conf(backend_str: str):

ibis/backends/datafusion/__init__.py

@@ -37,12 +37,9 @@ class Backend(BaseBackend):
 
     @property
     def version(self):
-        try:
-            import importlib.metadata as importlib_metadata
-        except ImportError:
-            # TODO: remove this when Python 3.9 support is dropped
-            import importlib_metadata
-        return importlib_metadata.version("datafusion")
+        import importlib.metadata
+
+        return importlib.metadata.version("datafusion")
 
     def do_connect(
         self,

ibis/backends/duckdb/__init__.py

@@ -93,12 +93,9 @@ def current_database(self) -> str:
     @property
     def version(self) -> str:
         # TODO: there is a `PRAGMA version` we could use instead
-        try:
-            import importlib.metadata as importlib_metadata
-        except ImportError:
-            # TODO: remove this when Python 3.9 support is dropped
-            import importlib_metadata
-        return importlib_metadata.version("duckdb")
+        import importlib.metadata
+
+        return importlib.metadata.version("duckdb")
 
     def do_connect(
         self,

ibis/tests/test_api.py

@@ -1,27 +1,28 @@
 from __future__ import annotations
 
 import sys
+from importlib.metadata import EntryPoint
 from typing import NamedTuple
 
 import pytest
 
 import ibis
 from ibis.backends.base import BaseBackend
 
-try:
-    import importlib.metadata as importlib_metadata
-except ImportError:
-    import importlib_metadata
 
-EntryPoint = importlib_metadata.EntryPoint
+def test_backends_are_cached():
+    assert isinstance(ibis.sqlite, BaseBackend)
+    del ibis.sqlite  # delete to force recreation
+    assert isinstance(ibis.sqlite, BaseBackend)
+    assert ibis.sqlite is ibis.sqlite
 
 
-def test_backends_are_cached():
-    # can't use `hasattr` since it calls `__getattr__`
-    if 'sqlite' in dir(ibis):
-        del ibis.sqlite
+def test_backends_tab_completion():
+    assert isinstance(ibis.sqlite, BaseBackend)
+    del ibis.sqlite  # delete to ensure not real attr
+    assert "sqlite" in dir(ibis)
     assert isinstance(ibis.sqlite, BaseBackend)
-    assert 'sqlite' in dir(ibis)
+    assert "sqlite" in dir(ibis)  # in dir even if already created
 
 
 def test_missing_backend():
@@ -31,32 +32,27 @@ def test_missing_backend():
 
 
 def test_multiple_backends(mocker):
-    if sys.version_info[:2] < (3, 8):
-        module = 'importlib_metadata'
-    else:
-        module = 'importlib.metadata'
-
-    api = f"{module}.entry_points"
-
     class Distribution(NamedTuple):
         entry_points: list[EntryPoint]
 
-    return_value = {
-        "ibis.backends": [
-            EntryPoint(
-                name="foo",
-                value='ibis.backends.backend1',
-                group="ibis.backends",
-            ),
-            EntryPoint(
-                name="foo",
-                value='ibis.backends.backend2',
-                group="ibis.backends",
-            ),
-        ],
-    }
-
-    mocker.patch(api, return_value=return_value)
+    entrypoints = [
+        EntryPoint(
+            name="foo",
+            value='ibis.backends.backend1',
+            group="ibis.backends",
+        ),
+        EntryPoint(
+            name="foo",
+            value='ibis.backends.backend2',
+            group="ibis.backends",
+        ),
+    ]
+    if sys.version_info < (3, 10):
+        return_value = {"ibis.backends": entrypoints}
+    else:
+        return_value = entrypoints
+
+    mocker.patch("importlib.metadata.entry_points", return_value=return_value)
 
     msg = r"\d+ packages found for backend 'foo'"
     with pytest.raises(RuntimeError, match=msg):