Simplify/add pyparsing error messages on mathtext/fontconfig errors.

`ParseBaseException.explain(0)` sets up the same "line and caret and
error message" as we previously did manually in _mathtext.  It requires
pyparsing 3.0.0 (2021), which is now permissible.

Also use the same detailed explanation on fontconfig pattern parse
failures.

Also suppress expression chaining in these cases, as the explain()
string already contains everything relevant.

Author: anntzer

doc/api/next_api_changes/development/23683-AL.rst

@@ -0,0 +1,2 @@
+pyparsing>=2.3.1 is now required
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

doc/devel/dependencies.rst

@@ -24,7 +24,7 @@ reference.
 * `NumPy <https://numpy.org>`_ (>= 1.19)
 * `packaging <https://pypi.org/project/packaging/>`_ (>= 20.0)
 * `Pillow <https://pillow.readthedocs.io/en/latest/>`_ (>= 6.2)
-* `pyparsing <https://pypi.org/project/pyparsing/>`_ (>= 2.2.1)
+* `pyparsing <https://pypi.org/project/pyparsing/>`_ (>= 2.3.1)
 * `setuptools <https://setuptools.readthedocs.io/en/latest/>`_
 
 

lib/matplotlib/__init__.py

@@ -203,7 +203,7 @@ def _check_versions():
             ("dateutil", "2.7"),
             ("kiwisolver", "1.0.1"),
             ("numpy", "1.19"),
-            ("pyparsing", "2.2.1"),
+            ("pyparsing", "2.3.1"),
     ]:
         module = importlib.import_module(modname)
         if parse_version(module.__version__) < parse_version(minver):

lib/matplotlib/_fontconfig_pattern.py

@@ -11,9 +11,11 @@
 
 from functools import lru_cache
 import re
+
 import numpy as np
-from pyparsing import (Literal, ZeroOrMore, Optional, Regex, StringEnd,
-                       ParseException, Suppress)
+from pyparsing import (
+    Literal, Optional, ParseException, Regex, StringEnd, Suppress, ZeroOrMore,
+)
 
 family_punc = r'\\\-:,'
 family_unescape = re.compile(r'\\([%s])' % family_punc).sub
@@ -125,14 +127,11 @@ def parse(self, pattern):
         props = self._properties = {}
         try:
             self._parser.parseString(pattern)
-        except self.ParseException as e:
-            raise ValueError(
-                "Could not parse font string: '%s'\n%s" % (pattern, e)) from e
-
+        except ParseException as err:
+            # explain becomes a plain method on pyparsing 3 (err.explain(0)).
+            raise ValueError("\n" + ParseException.explain(err, 0)) from None
         self._properties = None
-
         self._parser.resetCache()
-
         return props
 
     def _family(self, s, loc, tokens):

lib/matplotlib/_mathtext.py

@@ -15,8 +15,9 @@
 import numpy as np
 from pyparsing import (
     Empty, Forward, Literal, NotAny, oneOf, OneOrMore, Optional,
-    ParseBaseException, ParseExpression, ParseFatalException, ParserElement,
-    ParseResults, QuotedString, Regex, StringEnd, ZeroOrMore, pyparsing_common)
+    ParseBaseException, ParseException, ParseExpression, ParseFatalException,
+    ParserElement, ParseResults, QuotedString, Regex, StringEnd, ZeroOrMore,
+    pyparsing_common)
 
 import matplotlib as mpl
 from . import _api, cbook
@@ -1990,10 +1991,8 @@ def parse(self, s, fonts_object, fontsize, dpi):
         try:
             result = self._expression.parseString(s)
         except ParseBaseException as err:
-            raise ValueError("\n".join(["",
-                                        err.line,
-                                        " " * (err.column - 1) + "^",
-                                        str(err)])) from err
+            # explain becomes a plain method on pyparsing 3 (err.explain(0)).
+            raise ValueError("\n" + ParseException.explain(err, 0)) from None
         self._state_stack = None
         self._in_subscript_or_superscript = False
         # prevent operator spacing from leaking into a new expression

requirements/testing/minver.txt

@@ -6,6 +6,6 @@ kiwisolver==1.0.1
 numpy==1.19.0
 packaging==20.0
 pillow==6.2.1
-pyparsing==2.2.1
+pyparsing==2.3.1
 python-dateutil==2.7
 fonttools==4.22.0

setup.py

@@ -318,7 +318,7 @@ def make_release_tree(self, base_dir, files):
         "numpy>=1.19",
         "packaging>=20.0",
         "pillow>=6.2.0",
-        "pyparsing>=2.2.1",
+        "pyparsing>=2.3.1",
         "python-dateutil>=2.7",
     ] + (
         # Installing from a git checkout that is not producing a wheel.