geopandas: Mapping int/int64 to int32 for OGR_GMT format (#2592)

Co-authored-by: Wei Ji <23487320+weiji14@users.noreply.github.com>

pygmt/helpers/tempfile.py

@@ -126,18 +126,30 @@ def tempfile_from_geojson(geojson):
         E.g. '1a2b3c4d5e6.gmt'.
     """
     with GMTTempFile(suffix=".gmt") as tmpfile:
+        # pylint: disable=import-outside-toplevel
+        import geopandas as gpd
+
         os.remove(tmpfile.name)  # ensure file is deleted first
         ogrgmt_kwargs = {"filename": tmpfile.name, "driver": "OGR_GMT", "mode": "w"}
         try:
+            # Map int/int64 to int32 since OGR_GMT only supports 32-bit integer
+            # https://github.com/geopandas/geopandas/issues/967#issuecomment-842877704
+            # https://github.com/GenericMappingTools/pygmt/issues/2497
+            if geojson.index.name is None:
+                geojson.index.name = "index"
+            geojson = geojson.reset_index(drop=False)
+            schema = gpd.io.file.infer_schema(geojson)
+            for col, dtype in schema["properties"].items():
+                if dtype in ("int", "int64"):
+                    schema["properties"][col] = "int32"
+            ogrgmt_kwargs["schema"] = schema
             # Using geopandas.to_file to directly export to OGR_GMT format
             geojson.to_file(**ogrgmt_kwargs)
         except AttributeError:
-            # pylint: disable=import-outside-toplevel
             # Other 'geo' formats which implement __geo_interface__
             import json
 
             import fiona
-            import geopandas as gpd
 
             with fiona.Env():
                 jsontext = json.dumps(geojson.__geo_interface__)

pygmt/tests/baseline/test_geopandas_plot_int_dtypes.png.dvc

@@ -0,0 +1,4 @@
+outs:
+- md5: c1c6eda2a88adf4d96f18f4e0c5db4d5
+  size: 43582
+  path: test_geopandas_plot_int_dtypes.png

pygmt/tests/test_geopandas.py

@@ -3,7 +3,7 @@
 """
 import numpy.testing as npt
 import pytest
-from pygmt import Figure, info
+from pygmt import Figure, info, makecpt, which
 
 gpd = pytest.importorskip("geopandas")
 shapely = pytest.importorskip("shapely")
@@ -131,3 +131,54 @@ def test_geopandas_plot3d_non_default_circle():
         style="c0.2c",
     )
     return fig
+
+
+@pytest.mark.parametrize(
+    "dtype",
+    [
+        "int32",
+        "int64",
+        # Enable Int32/Int64 dtypes when geopandas>=0.13.3 is released with
+        # patch https://github.com/geopandas/geopandas/pull/2950
+        # pd.Int32Dtype(),
+        # pd.Int64Dtype(),
+    ],
+)
+@pytest.mark.mpl_image_compare(filename="test_geopandas_plot_int_dtypes.png")
+def test_geopandas_plot_int_dtypes(dtype):
+    """
+    Check that plotting a geopandas GeoDataFrame with integer columns works,
+    including int32 and int64 (non-nullable), Int32 and Int64 (nullable).
+
+    This is a regression test for
+    https://github.com/GenericMappingTools/pygmt/issues/2497
+    """
+    # Read shapefile in geopandas.GeoDataFrame
+    shapefile = which(
+        fname="@RidgeTest.shp @RidgeTest.shx @RidgeTest.dbf @RidgeTest.prj",
+        download="c",
+    )
+    gdf = gpd.read_file(shapefile[0])
+
+    # Reproject geometry and change dtype of NPOINTS column
+    gdf["geometry"] = (
+        gdf.to_crs(crs="EPSG:3857")
+        .buffer(distance=100000)
+        .to_crs(crs="OGC:CRS84")  # convert to lon/lat to prevent @null in PROJ CRS
+    )
+    gdf["NPOINTS"] = gdf.NPOINTS.astype(dtype=dtype)
+
+    # Plot figure with three polygons colored based on NPOINTS value
+    fig = Figure()
+    makecpt(cmap="lisbon", series=[10, 60, 10], continuous=True)
+    fig.plot(
+        data=gdf,
+        frame=True,
+        pen="1p,black",
+        close=True,
+        fill="+z",
+        cmap=True,
+        aspatial="Z=NPOINTS",
+    )
+    fig.colorbar()
+    return fig