Raise an error for zero increment grid (GenericMappingTools#1484)

Raise GMTInvalidInput error when xarray.DataArray
grid input has zero increment coordinates to prevent
segmentation fault in the PyGMT clib API.

Co-authored-by: Dongdong Tian <[email protected]>
Co-authored-by: Wei Ji <[email protected]>

pygmt/clib/conversion.py

@@ -82,7 +82,7 @@ def dataarray_to_matrix(grid):
     """
     if len(grid.dims) != 2:
         raise GMTInvalidInput(
-            "Invalid number of grid dimensions '{}'. Must be 2.".format(len(grid.dims))
+            f"Invalid number of grid dimensions '{len(grid.dims)}'. Must be 2."
         )
     # Extract region and inc from the grid
     region = []
@@ -96,9 +96,11 @@ def dataarray_to_matrix(grid):
         coord_inc = coord_incs[0]
         if not np.allclose(coord_incs, coord_inc):
             raise GMTInvalidInput(
-                "Grid appears to have irregular spacing in the '{}' dimension.".format(
-                    dim
-                )
+                f"Grid appears to have irregular spacing in the '{dim}' dimension."
+            )
+        if coord_inc == 0:
+            raise GMTInvalidInput(
+                f"Grid has a zero increment in the '{dim}' dimension."
             )
         region.extend(
             [

pygmt/tests/test_clib.py

@@ -743,6 +743,24 @@ def test_dataarray_to_matrix_inc_fails():
         dataarray_to_matrix(grid)
 
 
+def test_dataarray_to_matrix_zero_inc_fails():
+    """
+    Check that dataarray_to_matrix fails for zero increments grid.
+    """
+    data = np.ones((5, 5), dtype="float32")
+    x = np.linspace(0, 1, 5)
+    y = np.zeros_like(x)
+    grid = xr.DataArray(data, coords=[("y", y), ("x", x)])
+    with pytest.raises(GMTInvalidInput):
+        dataarray_to_matrix(grid)
+
+    y = np.linspace(0, 1, 5)
+    x = np.zeros_like(x)
+    grid = xr.DataArray(data, coords=[("y", y), ("x", x)])
+    with pytest.raises(GMTInvalidInput):
+        dataarray_to_matrix(grid)
+
+
 def test_get_default():
     """
     Make sure get_default works without crashing and gives reasonable results.