Figure.contour: Deprecate parameter "columns" to "incols" (remove in …

…v0.6.0) (#1303)

* Figure.contour: Add and deprecate parameter "columns" to "incols" (remove in v0.6.0)
* add test for deprecation warning

pygmt/src/contour.py

@@ -7,6 +7,7 @@
 from pygmt.helpers import (
     build_arg_string,
     data_kind,
+    deprecate_parameter,
     dummy_context,
     fmt_docstring,
     kwargs_to_strings,
@@ -15,6 +16,7 @@
 
 
 @fmt_docstring
+@deprecate_parameter("columns", "incols", "v0.4.0", remove_version="v0.6.0")
 @use_alias(
     A="annotation",
     B="frame",
@@ -30,7 +32,7 @@
     X="xshift",
     Y="yshift",
     c="panel",
-    i="columns",
+    i="incols",
     l="label",
     p="perspective",
     t="transparency",
@@ -104,6 +106,7 @@ def contour(self, x=None, y=None, z=None, data=None, **kwargs):
     {V}
     {XY}
     {c}
+    {i}
     {p}
     {t}
     """

pygmt/tests/test_contour.py

@@ -107,3 +107,37 @@ def test_contour_from_file(region):
         data=POINTS_DATA, projection="X10c", region=region, frame="af", pen="#ffcb87"
     )
     return fig
+
+
+@pytest.mark.mpl_image_compare(filename="test_contour_vec.png")
+def test_contour_deprecate_columns_to_incols(region):
+    """
+    Make sure that the old parameter "columns" is supported and it reports an
+    warning.
+
+    Modified from the test_contour_vec() test.
+    """
+    fig = Figure()
+    x, y = np.meshgrid(
+        np.linspace(region[0], region[1]), np.linspace(region[2], region[3])
+    )
+    x = x.flatten()
+    y = y.flatten()
+    z = (x - 0.5 * (region[0] + region[1])) ** 2 + 4 * y ** 2
+    z = np.exp(-z / 10 ** 2 * np.log(2))
+
+    # generate dataframe
+    # switch x and y from here onwards to simulate different column order
+    data = np.array([y, x, z]).T
+
+    with pytest.warns(expected_warning=FutureWarning) as record:
+        fig.contour(
+            data=data,
+            projection="X10c",
+            region=region,
+            frame="a",
+            pen=True,
+            columns=[1, 0, 2],
+        )
+        assert len(record) == 1  # check that only one warning was raised
+    return fig