add Andy Harrington's version qualifier checking code

1 files changed, 98 insertions, 0 deletions

diff --git a/versionpredicate.py b/versionpredicate.py
new file mode 100644
index 0000000..ef72954
--- /dev/null
+++ b/versionpredicate.py
@@ -0,0 +1,98 @@
+"""Module for parsing and testing package version predicate strings.
+"""
+import re
+import operator
+
+import distutils.version
+
+re_validPackage = re.compile(r"(?i)^\s*([a-z_]\w*(?:\.[a-z_]\w*)*)(.*)")
+# (package) (rest)
+
+re_paren = re.compile(r"^\s*\((.*)\)\s*$") # (list) inside of parentheses
+re_splitComparison = re.compile(r"^\s*(<=|>=|<|>|!=|==)\s*([^\s,]+)\s*$")
+# (comp) (version)
+
+def splitUp(pred):
+   """Parse a single version comparison.
+   Return (comparison string, StrictVersion)
+   """
+   res = re_splitComparison.match(pred)
+   if not res:
+       raise ValueError, "Bad package restriction syntax:  " + pred
+   comp, verStr = res.groups()
+   return (comp, distutils.version.StrictVersion(verStr))
+
+compmap = {"<": operator.lt, "<=": operator.le, "==": operator.eq,
+           ">": operator.gt, ">=": operator.ge, "!=": operator.ne}
+
+class VersionPredicate:
+   """Parse and test package version predicates.
+
+   >>> v = VersionPredicate("pyepat.abc (>1.0, <3333.3a1, !=1555.1b3)")
+   >>> print v
+   pyepat.abc (> 1.0, < 3333.3a1, != 1555.1b3)
+   >>> v.satisfied_by("1.1")
+   True
+   >>> v.satisfied_by("1.4")
+   True
+   >>> v.satisfied_by("1.0")
+   False
+   >>> v.satisfied_by("4444.4")
+   False
+   >>> v.satisfied_by("1555.1b3")
+   False
+   >>> v = VersionPredicate("pat( ==  0.1  )  ")
+   >>> v.satisfied_by("0.1")
+   True
+   >>> v.satisfied_by("0.2")
+   False
+   >>> v = VersionPredicate("p1.p2.p3.p4(>=1.0, <=1.3a1, !=1.2zb3)")
+   Traceback (most recent call last):
+   ...
+   ValueError: invalid version number '1.2zb3'
+
+   """
+
+   def __init__(self, versionPredicateStr):
+       """Parse a version predicate string.
+       """
+       # Fields:
+       #    name:  package name
+       #    pred:  list of (comparison string, StrictVersion)
+
+       versionPredicateStr = versionPredicateStr.strip()
+       if not versionPredicateStr:
+           raise ValueError, "Empty package restriction"
+       match = re_validPackage.match(versionPredicateStr)
+       if not match:
+           raise ValueError, "Bad package name in " + versionPredicateStr
+       self.name, paren = match.groups()
+       paren = paren.strip()
+       if paren:
+           match = re_paren.match(paren)
+           if not match:
+               raise ValueError, "Expected parenthesized list: " + paren
+           str = match.groups()[0]
+           self.pred = [splitUp(aPred) for aPred in str.split(",")]
+           if not self.pred:
+               raise ValueError("Empty Parenthesized list in %r" 
+                                % versionPredicateStr )
+       else:
+           self.pred=[]
+
+   def __str__(self):
+       if self.pred:
+           seq = [cond + " " + str(ver) for cond, ver in self.pred]
+           return self.name + " (" + ", ".join(seq) + ")"
+       else:
+           return self.name
+
+   def satisfied_by(self, version):
+       """True if version is compatible with all the predicates in self.
+          The parameter version must be acceptable to the StrictVersion
+          constructor.  It may be either a string or StrictVersion.
+       """
+       for cond, ver in self.pred:
+           if not compmap[cond](version, ver):
+               return False
+       return True