Add generic try_import helper and adopt it for optional deps

lumen/sources/duckdb.py

@@ -19,9 +19,7 @@
 from ..transforms.sql import (
     SQLCount, SQLFilter, SQLLimit, SQLSelectFrom,
 )
-from ..util import (
-    detect_file_encoding, normalize_table_name, try_import_geopandas,
-)
+from ..util import detect_file_encoding, normalize_table_name, try_import
 from .base import BaseSQLSource, Source, cached
 
 if TYPE_CHECKING:
@@ -530,7 +528,7 @@ def _fetch_df(
         wrapped = f'SELECT {selected} FROM ({sql_expr})'
         rel = cursor.execute(wrapped, params) if params else cursor.execute(wrapped)
         df = rel.fetch_df(date_as_object=date_as_object)
-        if gpd := try_import_geopandas():
+        if gpd := try_import("geopandas"):
             for col in geom_cols:
                 df[col] = gpd.GeoSeries.from_wkb(
                     df[col].apply(bytes), crs=self.geometry_crs

lumen/tests/ai/test_controls/test_upload.py

@@ -9,13 +9,7 @@
 from lumen.ai.controls import SourceResult, UploadedFileRow
 from lumen.ai.controls.ingest.utils import read_geo_file
 from lumen.sources.duckdb import DuckDBSource
-
-try:
-    import geopandas as gpd
-
-    from shapely.geometry import Polygon
-except ImportError:
-    gpd = None
+from lumen.tests.utils import Polygon, gpd, requires_geopandas
 
 
 @pytest.mark.asyncio
@@ -373,11 +367,10 @@ def test_upload_button_label_is_explicit(self, upload_controls):
         assert upload_controls._add_button.name == "Upload file(s)"
 
 
+@requires_geopandas
 def test_read_geo_file_captures_crs():
     """read_geo_file surfaces the source CRS in source_params so DuckDBSource
     can reapply it after the WKB roundtrip (gh-1904)."""
-    if gpd is None:
-        pytest.skip("geopandas is not installed")
     gdf = gpd.GeoDataFrame(
         {"name": ["a"]}, geometry=[Polygon([(0, 0), (1, 0), (1, 1)])], crs="EPSG:4326"
     )

lumen/tests/sources/test_duckdb.py

@@ -8,6 +8,7 @@
 import pandas as pd
 import pytest
 
+from lumen.tests.utils import Polygon, gpd
 from lumen.transforms.sql import SQLGroupBy
 
 try:
@@ -18,13 +19,6 @@
 except ImportError:
     pytestmark = pytest.mark.skip(reason="Duckdb is not installed")
 
-try:
-    import geopandas as gpd
-
-    from shapely.geometry import Polygon
-except ImportError:
-    gpd = None
-
 
 @pytest.fixture
 def duckdb_file_source():

lumen/tests/sources/test_optional_imports.py

@@ -7,14 +7,15 @@
 
 import builtins
 import importlib
+import json
 import sys
 
 from pathlib import Path
 from unittest.mock import patch
 
 import pytest
 
-from lumen.util import try_import_geopandas, try_import_xarray
+from lumen.util import try_import, try_import_xarray
 
 # Each entry: (module_path, class_name, guard_package, pip_extra)
 OPTIONAL_SOURCES = [
@@ -88,14 +89,35 @@ def mock_import(name, *args, **kwargs):
         sys.modules.update(saved)
 
 
+def test_try_import_returns_module_when_installed():
+    """try_import returns the module object for an importable module."""
+    assert try_import("json") is json
+
+
+def test_try_import_returns_none_when_missing():
+    """try_import returns None (not raises) for a module that cannot be imported."""
+    assert try_import("a_module_that_does_not_exist_xyz") is None
+
+
+def test_try_import_load_false_returns_already_imported_module():
+    """try_import(load=False) returns a module that is already imported."""
+    assert try_import("json", load=False) is json
+
+
+def test_try_import_load_false_never_imports():
+    """try_import(load=False) must not trigger an import, only consult sys.modules."""
+    with patch("lumen.util.importlib.import_module", side_effect=AssertionError("imported")):
+        assert try_import("a_module_that_does_not_exist_xyz", load=False) is None
+
+
 def test_try_import_geopandas_returns_module_when_installed():
-    """try_import_geopandas returns the geopandas module when importable."""
+    """try_import returns the geopandas module when it is importable."""
     gpd = pytest.importorskip("geopandas")
-    assert try_import_geopandas() is gpd
+    assert try_import("geopandas") is gpd
 
 
 def test_try_import_geopandas_none_when_missing():
-    """try_import_geopandas returns None (not raises) when geopandas is absent."""
+    """try_import returns None (not raises) when geopandas is absent."""
     real_import = builtins.__import__
 
     def mock_import(name, *args, **kwargs):
@@ -109,7 +131,7 @@ def mock_import(name, *args, **kwargs):
     }
     try:
         with patch("builtins.__import__", side_effect=mock_import):
-            assert try_import_geopandas() is None
+            assert try_import("geopandas") is None
     finally:
         sys.modules.update(saved)
 

lumen/tests/test_pipeline.py

@@ -15,19 +15,13 @@
 except Exception:
     duckdb = None
 
-try:
-    import geopandas as gpd
-
-    from shapely.geometry import Polygon
-except Exception:
-    gpd = None
-
 from panel.widgets import Select
 
 from lumen.filters.base import ConstantFilter
 from lumen.pipeline import Pipeline
 from lumen.sources.intake_sql import IntakeSQLSource
 from lumen.state import state
+from lumen.tests.utils import Polygon, gpd, requires_geopandas
 from lumen.transforms.base import Columns, Transform
 from lumen.transforms.sql import SQLColumns, SQLGroupBy
 from lumen.validation import ValidationError
@@ -400,10 +394,11 @@ def apply(self, table):
     assert not pipeline._update_widget.loading
 
 
+@requires_geopandas
 def test_pipeline_preserves_geodataframe():
     """A GeoDataFrame survives source -> filter -> Pipeline.data without downcast."""
-    if gpd is None or duckdb is None:
-        pytest.skip("geopandas or duckdb is not installed")
+    if duckdb is None:
+        pytest.skip("duckdb is not installed")
     try:
         source = DuckDBSource(
             uri=':memory:',

lumen/tests/test_schema.py

@@ -4,20 +4,13 @@
 
 import pandas as pd
 import panel as pn
-import pytest
 
 from panel_material_ui import Checkbox, FloatSlider, Select
 
 from lumen.schema import JSONSchema
+from lumen.tests.utils import Polygon, gpd, requires_geopandas
 from lumen.util import get_dataframe_schema
 
-try:
-    import geopandas as gpd
-
-    from shapely.geometry import Polygon
-except ImportError:
-    gpd = None
-
 
 def test_boolean_schema():
     json_schema = JSONSchema(schema={'bool': {'type': 'boolean'}}, multi=False)
@@ -41,10 +34,9 @@ def test_enum_schema():
     assert widget.options == ['A', 'B', 'C']
 
 
+@requires_geopandas
 def test_get_dataframe_schema_geometry():
     """A geometry column is emitted as a compact, JSON-serializable marker."""
-    if gpd is None:
-        pytest.skip("geopandas is not installed")
     gdf = gpd.GeoDataFrame(
         {
             "name": ["a", "b"],
@@ -70,10 +62,9 @@ def test_get_dataframe_schema_geometry():
     json.dumps(schema)
 
 
+@requires_geopandas
 def test_get_dataframe_schema_geometry_empty():
     """An empty GeoDataFrame yields geometry_type 'unknown' without raising."""
-    if gpd is None:
-        pytest.skip("geopandas is not installed")
     gdf = gpd.GeoDataFrame({"name": [], "geometry": []})
     schema = get_dataframe_schema(gdf)
     assert schema["items"]["properties"]["geometry"]["format"] == "geometry"

lumen/tests/utils.py

@@ -0,0 +1,20 @@
+"""Shared test helpers for optional geospatial dependencies.
+
+Importing geopandas at module top would break collection where it is not
+installed, so guard it once here and let tests import ``gpd``/``Polygon`` and
+skip via ``requires_geopandas`` instead of repeating the guard per file.
+"""
+import pytest
+
+try:
+    import geopandas as gpd
+
+    from shapely.geometry import Polygon
+except ImportError:
+    gpd = None
+    Polygon = None
+
+# geopandas depends on shapely, so a single geopandas check covers both.
+requires_geopandas = pytest.mark.skipif(
+    gpd is None, reason="geopandas is not installed"
+)

lumen/tests/views/test_base.py

@@ -10,26 +10,14 @@
 from lumen.panel import DownloadButton
 from lumen.pipeline import Pipeline
 from lumen.sources.base import FileSource
+from lumen.sources.duckdb import DuckDBSource
 from lumen.state import state
+from lumen.tests.utils import Polygon, gpd, requires_geopandas
 from lumen.variables.base import Variables
 from lumen.views.base import (
     DeckGLView, Panel, Table, VegaLiteView, View, hvOverlayView, hvPlotView,
 )
 
-try:
-    import geopandas as gpd
-
-    from shapely.geometry import Polygon
-
-    from lumen.sources.duckdb import DuckDBSource
-    _GEO_DEPS = True
-except ImportError:
-    _GEO_DEPS = False
-
-requires_geo = pytest.mark.skipif(
-    not _GEO_DEPS, reason="geopandas, shapely or duckdb not installed"
-)
-
 # geoviews is checked without importing it: importing geoviews (-> matplotlib)
 # at collection under xdist can deadlock the font cache on macOS. hvplot imports
 # it lazily when the geometry plot is actually rendered.
@@ -390,7 +378,7 @@ def test_vega_datasets(set_root):
     pd.testing.assert_frame_equal(final_spec["datasets"]["test"], pipeline.data)
 
 
-@requires_geo
+@requires_geopandas
 @requires_geoviews
 def test_view_hvplot_geometry_auto_kind():
     """A GeoDataFrame view renders its geometry with an auto-selected kind."""
@@ -427,7 +415,7 @@ def test_view_hvplot_geometry_auto_kind():
     assert type(plot).__name__ == 'Polygons'
 
 
-@requires_geo
+@requires_geopandas
 def test_table_view_geometry_rendered_as_wkt():
     """Table view converts geometry columns to WKT so Bokeh can serialize them."""
     try:
@@ -458,7 +446,7 @@ def test_table_view_geometry_rendered_as_wkt():
     view.get_panel()
 
 
-@requires_geo
+@requires_geopandas
 def test_deckgl_view_geometry_as_geojson():
     """DeckGLView emits a GeoDataFrame as a GeoJSON FeatureCollection for layers."""
     try:

lumen/util.py

@@ -510,21 +510,28 @@ def normalize_table_name(name: str) -> str:
     return re.sub(r'\W+', '_', name).strip('_').lower()
 
 
-def try_import_xarray():
-    """Import and return xarray, or None if xarray or xarray-sql is unavailable."""
+def try_import(module_name, load=True):
+    """Import and return a module, or None if it is unavailable.
+
+    With load=False the module is returned only if it has already been
+    imported, a cheap check that never triggers an import; this lets a hot path
+    ask whether an optional dependency is in play without paying to import it.
+    With load=True (the default) the module is imported on demand.
+    """
+    if not load:
+        return sys.modules.get(module_name)
     try:
-        import xarray
-        import xarray_sql  # noqa
-        return xarray
+        return importlib.import_module(module_name)
     except ImportError:
         return None
 
 
-def try_import_geopandas():
-    """Import and return geopandas, or None if it is not installed."""
+def try_import_xarray():
+    """Import and return xarray, or None if xarray or xarray-sql is unavailable."""
     try:
-        import geopandas
-        return geopandas
+        import xarray
+        import xarray_sql  # noqa
+        return xarray
     except ImportError:
         return None
 
@@ -536,7 +543,7 @@ def is_geodataframe(df):
     a GeoDataFrame unless geopandas is loaded, so this stays cheap on the hot
     path and never speculatively imports geopandas.
     """
-    gpd = sys.modules.get("geopandas")
+    gpd = try_import("geopandas", load=False)
     return gpd is not None and isinstance(df, gpd.GeoDataFrame)
 
 
@@ -546,7 +553,7 @@ def geometry_columns(df):
     Empty when geopandas is not imported (no geometry column can exist without
     it) or df has no geometry columns; never speculatively imports geopandas.
     """
-    gpd = sys.modules.get("geopandas")
+    gpd = try_import("geopandas", load=False)
     if gpd is None:
         return []
     return [c for c in df.columns if isinstance(df[c].dtype, gpd.array.GeometryDtype)]
@@ -563,7 +570,7 @@ def geometry_to_wkt(df):
     geom_cols = geometry_columns(df)
     if not geom_cols:
         return df
-    gpd = sys.modules["geopandas"]
+    gpd = try_import("geopandas", load=False)
     df = pd.DataFrame(df).copy()
     for col in geom_cols:
         df[col] = gpd.GeoSeries(df[col]).to_wkt()