Improve the error message when GMTInvalidInput error is raised for basemap (#729)

Author: willschlitzer

pygmt/base_plotting.py

@@ -1167,8 +1167,10 @@ def basemap(self, **kwargs):
 
         """
         kwargs = self._preprocess(**kwargs)
-        if not ("B" in kwargs or "L" in kwargs or "T" in kwargs):
-            raise GMTInvalidInput("At least one of B, L, or T must be specified.")
+        if not ("B" in kwargs or "L" in kwargs or "Td" in kwargs or "Tm" in kwargs):
+            raise GMTInvalidInput(
+                "At least one of frame, map_scale, compass, or rose must be specified."
+            )
         with Session() as lib:
             lib.call_module("basemap", build_arg_string(kwargs))
 

pygmt/tests/test_basemap.py

@@ -80,3 +80,25 @@ def test_basemap_aliases():
     fig = Figure()
     fig.basemap(region=[0, 360, -90, 90], projection="W7i", frame=True)
     return fig
+
+
+@check_figures_equal()
+def test_basemap_rose():
+    "Create a map with coast and use basemap to add a rose"
+    fig_ref, fig_test = Figure(), Figure()
+    fig_ref.coast(R="127.5/128.5/26/27", W="1/0.5p")
+    fig_ref.basemap(Td="jBR+w5c")
+    fig_test.coast(region=[127.5, 128.5, 26, 27], shorelines="1/0.5p")
+    fig_test.basemap(rose="jBR+w5c")
+    return fig_ref, fig_test
+
+
+@check_figures_equal()
+def test_basemap_compass():
+    "Create a map with coast and use basemap to add a compass"
+    fig_ref, fig_test = Figure(), Figure()
+    fig_ref.coast(R="127.5/128.5/26/27", W="1/0.5p")
+    fig_ref.basemap(Tm="jBR+w5c+d11.5")
+    fig_test.coast(region=[127.5, 128.5, 26, 27], shorelines="1/0.5p")
+    fig_test.basemap(compass="jBR+w5c+d11.5")
+    return fig_ref, fig_test