Monkey patch pyparsing so that we can support pyparsing >= 1.5.6 on both Python 2 and 3 without loads of deprecation warnings.

mdboom · mdboom · commit 0fa8a9ae00d7 · 2013-08-07T12:21:11.000-04:00
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -120,6 +120,16 @@
             "matplotlib requires pyparsing >= {0}".format(
                 '.'.join(str(x) for x in _required)))
 
+    # pyparsing 1.5.6 does not have <<= on the Forward class, but
+    # pyparsing 2.0.0 and later will spew deprecation warnings if
+    # using << instead.  In order to support pyparsing 1.5.6 and above
+    # with a common code base, this small monkey patch is applied.
+    if not hasattr(pyparsing.Forward, '__ilshift__'):
+        def _forward_ilshift(self, other):
+            self.__lshift__(other)
+            return self
+        pyparsing.Forward.__ilshift__ = _forward_ilshift
+
 import os, re, shutil, warnings
 import distutils.sysconfig
 import distutils.version
diff --git a/lib/matplotlib/mathtext.py b/lib/matplotlib/mathtext.py
@@ -40,7 +40,14 @@
      ParseResults, Suppress, oneOf, StringEnd, ParseFatalException, \
      FollowedBy, Regex, ParserElement, QuotedString, ParseBaseException
 
-ParserElement.enablePackrat()
+# Enable packrat parsing
+if (sys.version_info[0] >= 3 and
+    [int(x) for x in pyparsing.__version__.split('.')] < [2, 0, 0]):
+    warn("Due to a bug in pyparsing <= 2.0.0 on Python 3.x, packrat parsing "
+         "has been disabled.  Mathtext rendering will be much slower as a "
+         "result.  Install pyparsing 2.0.0 or later to improve performance.")
+else:
+    ParserElement.enablePackrat()
 
 from matplotlib.afm import AFM
 from matplotlib.cbook import Bunch, get_realpath_and_stat, \
diff --git a/setupext.py b/setupext.py
@@ -971,15 +971,25 @@ def check(self):
                 "support. pip/easy_install may attempt to install it "
                 "after matplotlib.")
 
-        required = [2, 0, 1]
+        required = [1, 5, 6]
         if [int(x) for x in pyparsing.__version__.split('.')] < required:
             return (
                 "matplotlib requires pyparsing >= {0}".format(
                     '.'.join(str(x) for x in required)))
+
+        if sys.version_info[0] == 2:
+            if pyparsing.__version__ == "2.0.0":
+                return (
+                    "pyparsing 2.0.0 is not compatible with Python 2.x")
+
         return "using pyparsing version %s" % pyparsing.__version__
 
     def get_install_requires(self):
-        return ['pyparsing>=2.0.1']
+        if sys.version_info[0] >= 3:
+            return ['pyparsing>=1.5.6']
+        else:
+            # pyparsing >= 2.0.0 is not compatible with Python 2
+            return ['pyparsing>=1.5.6,!=2.0.0']
 
 
 class BackendAgg(OptionalBackendPackage):
