pygmt.grdfill: Add new parameter 'inquire' to inquire the bounds of holes

Author: seisman

pygmt/src/grdfill.py

@@ -76,6 +76,7 @@ def grdfill(
     gridfill: str | xr.DataArray | None = None,
     neighborfill: float | bool | None = None,
     splinefill: float | bool | None = None,
+    inquire: bool = False,
     **kwargs,
 ) -> xr.DataArray | None:
     r"""
@@ -111,6 +112,9 @@ def grdfill(
     hole : float
         Set the node value used to identify a point as a member of a hole [Default is
         NaN].
+    inquire
+        Output the bounds of each hole. The bounds are 2-D numpy arrays in the form of
+        (west, east, south, north). No grid fill takes place and ``outgrid`` is ignored.
     mode : str
         Specify the hole-filling algorithm to use. Choose from **c** for constant fill
         and append the constant value, **n** for nearest neighbor (and optionally append
@@ -155,10 +159,34 @@ def grdfill(
         # Determine the -A option from the fill parameters.
         kwargs["A"] = _parse_fill_mode(constantfill, gridfill, neighborfill, splinefill)
 
-    if kwargs.get("A") is None and kwargs.get("L") is None:
-        msg = "At least parameter 'mode' or 'L' must be specified."
+    if kwargs.get("A") is None and not inquire:
+        msg = (
+            "Need to specify parameter 'constantfill'/'gridfill'/'neighborfill'/"
+            "'splinefill' or 'inquire'."
+        )
+        raise GMTInvalidInput(msg)
+    if kwargs.get("A") is not None and inquire:
+        msg = (
+            "Parameters 'constantfill'/'gridfill'/'neighborfill'/'splinefill' and "
+            "'inquire' are mutually exclusive."
+        )
         raise GMTInvalidInput(msg)
 
+    # Inquire only, no grid fill.
+    if inquire:
+        kwargs["L"] = True
+        with Session() as lib:
+            with (
+                lib.virtualfile_in(check_kind="raster", data=grid) as vingrd,
+                lib.virtualfile_out(kind="dataset") as vouttbl,
+            ):
+                lib.call_module(
+                    module="grdfill",
+                    args=build_arg_list(kwargs, infile=vingrd, outfile=vouttbl),
+                )
+                return lib.virtualfile_to_dataset(vfname=vouttbl, output_type="numpy")
+
+    # Fill the grid:
     with Session() as lib:
         with (
             lib.virtualfile_in(check_kind="raster", data=grid) as vingrd,