Fix validation of linestyle in rcparams and cycler.

anntzer · anntzer · commit 2b5b24e4a49b · 2019-12-04T00:09:58.000+01:00
Correcly use _validate_linestyle instead of validate_stringlist in the
cycler linestyle validator.  For compat, support both the (on, off, on,
off, ...) and (offset, (on, off, on, off, ...)) forms.  Don't support
passing on, off, etc. as *individual* separate strings anymore as that's
not a realistic use case (unlike passing the whole thing as a single
string, which is supported for parsing the rc file).
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -14,13 +14,17 @@
 :file:`matplotlibrc.template` in matplotlib's root source directory.
 """
 
+import ast
 from collections.abc import Iterable, Mapping
 from functools import partial, reduce
 import logging
+from numbers import Number
 import operator
 import os
 import re
 
+import numpy as np
+
 import matplotlib as mpl
 from matplotlib import animation, cbook
 from matplotlib.cbook import ls_mapper
@@ -532,6 +536,50 @@ def validate_ps_distiller(s):
                          'ghostscript or xpdf')
 
 
+# A validator dedicated to the named line styles, based on the items in
+# ls_mapper, and a list of possible strings read from Line2D.set_linestyle
+_validate_named_linestyle = ValidateInStrings(
+    'linestyle',
+    [*ls_mapper.keys(), *ls_mapper.values(), 'None', 'none', ' ', ''],
+    ignorecase=True)
+
+
+def _validate_linestyle(ls):
+    """
+    A validator for all possible line styles, the named ones *and*
+    the on-off ink sequences.
+    """
+    if isinstance(ls, str):
+        try:  # Look first for a valid named line style, like '--' or 'solid'.
+            return _validate_named_linestyle(ls)
+        except ValueError:
+            pass
+        try:
+            ls = ast.literal_eval(ls)
+        except (SyntaxError, ValueError):
+            pass  # Will error with the ValueError at the end.
+
+    def _is_iterable_not_string_like(x):
+        # Explicitly exclude bytes/bytearrays so that they are not
+        # nonsensically interpreted as sequences of numbers (codepoints).
+        return np.iterable(x) and not isinstance(x, (str, bytes, bytearray))
+
+    # (offset, (on, off, on, off, ...))
+    if (_is_iterable_not_string_like(ls)
+            and len(ls) == 2
+            and isinstance(ls[0], (type(None), Number))
+            and _is_iterable_not_string_like(ls[1])
+            and len(ls[1]) % 2 == 0
+            and all(isinstance(elem, Number) for elem in ls[1])):
+        return ls
+    # For backcompat: (on, off, on, off, ...); the offset is implicitly None.
+    if (_is_iterable_not_string_like(ls)
+            and len(ls) % 2 == 0
+            and all(isinstance(elem, Number) for elem in ls)):
+        return (None, ls)
+    raise ValueError(f"linestyle {ls!r} is not a valid on-off ink sequence.")
+
+
 validate_joinstyle = ValidateInStrings('joinstyle',
                                        ['miter', 'round', 'bevel'],
                                        ignorecase=True)
@@ -748,7 +796,7 @@ def validate_hatch(s):
         'color': _listify_validator(validate_color_for_prop_cycle,
                                     allow_stringlist=True),
         'linewidth': validate_floatlist,
-        'linestyle': validate_stringlist,
+        'linestyle': _listify_validator(_validate_linestyle),
         'facecolor': validate_colorlist,
         'edgecolor': validate_colorlist,
         'joinstyle': validate_joinstylelist,
@@ -970,43 +1018,6 @@ def validate_webagg_address(s):
     raise ValueError("'webagg.address' is not a valid IP address")
 
 
-# A validator dedicated to the named line styles, based on the items in
-# ls_mapper, and a list of possible strings read from Line2D.set_linestyle
-_validate_named_linestyle = ValidateInStrings(
-    'linestyle',
-    [*ls_mapper.keys(), *ls_mapper.values(), 'None', 'none', ' ', ''],
-    ignorecase=True)
-
-
-def _validate_linestyle(ls):
-    """
-    A validator for all possible line styles, the named ones *and*
-    the on-off ink sequences.
-    """
-    # Look first for a valid named line style, like '--' or 'solid' Also
-    # includes bytes(-arrays) here (they all fail _validate_named_linestyle);
-    # otherwise, if *ls* is of even-length, it will be passed to the instance
-    # of validate_nseq_float, which will return an absurd on-off ink
-    # sequence...
-    if isinstance(ls, (str, bytes, bytearray)):
-        return _validate_named_linestyle(ls)
-
-    # Look for an on-off ink sequence (in points) *of even length*.
-    # Offset is set to None.
-    try:
-        if len(ls) % 2 != 0:
-            raise ValueError("the linestyle sequence {!r} is not of even "
-                             "length.".format(ls))
-
-        return (None, validate_nseq_float()(ls))
-
-    except (ValueError, TypeError):
-        # TypeError can be raised inside the instance of validate_nseq_float,
-        # by wrong types passed to float(), like NoneType.
-        raise ValueError("linestyle {!r} is not a valid on-off ink "
-                         "sequence.".format(ls))
-
-
 validate_axes_titlelocation = ValidateInStrings('axes.titlelocation', ['left', 'center', 'right'])
 
 # a map from key -> value, converter
diff --git a/lib/matplotlib/tests/test_rcparams.py b/lib/matplotlib/tests/test_rcparams.py
@@ -370,16 +370,16 @@ def generate_validator_testcases(valid):
                      ('', ''), (' ', ' '),
                      ('None', 'none'), ('none', 'none'),
                      ('DoTtEd', 'dotted'),  # case-insensitive
-                     (['1.23', '4.56'], (None, [1.23, 4.56])),
+                     ('1, 3', (None, (1, 3))),
                      ([1.23, 456], (None, [1.23, 456.0])),
                      ([1, 2, 3, 4], (None, [1.0, 2.0, 3.0, 4.0])),
+                     ((None, [1, 2]), (None, [1, 2])),
+                     ((0, [1, 2]), (0, [1, 2])),
+                     ((-1, [1, 2]), (-1, [1, 2])),
                      ),
          'fail': (('aardvark', ValueError),  # not a valid string
                   (b'dotted', ValueError),
                   ('dotted'.encode('utf-16'), ValueError),
-                  ((None, [1, 2]), ValueError),  # (offset, dashes) != OK
-                  ((0, [1, 2]), ValueError),  # idem
-                  ((-1, [1, 2]), ValueError),  # idem
                   ([1, 2, 3], ValueError),  # sequence with odd length
                   (1.23, ValueError),  # not a sequence
                   )
