Ensure x/y are not None for dictionary input

Author: seisman

pygmt/helpers/utils.py

@@ -12,6 +12,7 @@
 import time
 import webbrowser
 from collections.abc import Iterable, Mapping, Sequence
+from itertools import islice
 from pathlib import Path
 from typing import Any, Literal
 
@@ -41,7 +42,7 @@
 ]
 
 
-def _validate_data_input(
+def _validate_data_input(  # noqa: PLR0912
     data=None, x=None, y=None, z=None, required_z=False, required_data=True, kind=None
 ) -> None:
     """
@@ -143,6 +144,16 @@ def _validate_data_input(
                     raise GMTInvalidInput(msg)
                 if hasattr(data, "data_vars") and len(data.data_vars) < 3:  # xr.Dataset
                     raise GMTInvalidInput(msg)
+        if kind == "vectors" and isinstance(data, dict):
+            # Iterator over the up-to-3 first elements.
+            arrays = list(islice(data.values(), 3))
+            # A dictionary holding multiple columns
+            if len(arrays) < 2 or any(v is None for v in arrays[:2]):  # Check x/y
+                msg = "Must provide both x and y."
+                raise GMTInvalidInput(msg)
+            if required_z and (len(arrays) < 3 or arrays[2] is None):  # Check z
+                msg = "Must provide x, y, and z."
+                raise GMTInvalidInput(msg)
 
 
 def _is_printable_ascii(argstr: str) -> bool: