Fix rcParams validator for dashes.

anntzer · anntzer · commit f964afdc3547 · 2020-05-19T00:50:48.000+02:00
Valid dash-patterns are actually just lists of floats:
```
rcParams["lines.dashed_pattern"] = (1, None)
plt.plot([1, 2], ls="--")
```
throws
```
TypeError: unsupported operand type(s) for +: 'float' and 'NoneType'
```
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -793,7 +793,7 @@ def validate_hatch(s):
 
 
 validate_hatchlist = _listify_validator(validate_hatch)
-validate_dashlist = _listify_validator(validate_nseq_float(allow_none=True))
+validate_dashlist = _listify_validator(validate_floatlist)
 
 
 _prop_validators = {
@@ -1069,9 +1069,9 @@ def _convert_validator_spec(key, conv):
     "lines.solid_joinstyle": validate_joinstyle,
     "lines.dash_capstyle":   validate_capstyle,
     "lines.solid_capstyle":  validate_capstyle,
-    "lines.dashed_pattern":  validate_nseq_float(allow_none=True),
-    "lines.dashdot_pattern": validate_nseq_float(allow_none=True),
-    "lines.dotted_pattern":  validate_nseq_float(allow_none=True),
+    "lines.dashed_pattern":  validate_floatlist,
+    "lines.dashdot_pattern": validate_floatlist,
+    "lines.dotted_pattern":  validate_floatlist,
     "lines.scale_dashes":    validate_bool,
 
     # marker props
diff --git a/lib/matplotlib/tests/test_cycles.py b/lib/matplotlib/tests/test_cycles.py
@@ -111,7 +111,7 @@ def test_valid_input_forms():
     ax.set_prop_cycle('color', np.array([[1, 0, 0],
                                          [0, 1, 0],
                                          [0, 0, 1]]))
-    ax.set_prop_cycle('dashes', [[], [13, 2], [8, 3, 1, 3], [None, None]])
+    ax.set_prop_cycle('dashes', [[], [13, 2], [8, 3, 1, 3]])
     ax.set_prop_cycle(lw=[1, 2], color=['k', 'w'], ls=['-', '--'])
     ax.set_prop_cycle(lw=np.array([1, 2]),
                       color=np.array(['k', 'w']),
