1 files changed, 146 insertions, 0 deletions
diff --git a/third_party/python/packaging/packaging/requirements.py b/third_party/python/packaging/packaging/requirements.py
new file mode 100644
index 0000000000..53f9a3aa42
--- /dev/null
+++ b/third_party/python/packaging/packaging/requirements.py
@@ -0,0 +1,146 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+import re
+import string
+import urllib.parse
+from typing import List, Optional as TOptional, Set
+
+from pyparsing import (  # noqa
+    Combine,
+    Literal as L,
+    Optional,
+    ParseException,
+    Regex,
+    Word,
+    ZeroOrMore,
+    originalTextFor,
+    stringEnd,
+    stringStart,
+)
+
+from .markers import MARKER_EXPR, Marker
+from .specifiers import LegacySpecifier, Specifier, SpecifierSet
+
+
+class InvalidRequirement(ValueError):
+    """
+    An invalid requirement was found, users should refer to PEP 508.
+    """
+
+
+ALPHANUM = Word(string.ascii_letters + string.digits)
+
+LBRACKET = L("[").suppress()
+RBRACKET = L("]").suppress()
+LPAREN = L("(").suppress()
+RPAREN = L(")").suppress()
+COMMA = L(",").suppress()
+SEMICOLON = L(";").suppress()
+AT = L("@").suppress()
+
+PUNCTUATION = Word("-_.")
+IDENTIFIER_END = ALPHANUM | (ZeroOrMore(PUNCTUATION) + ALPHANUM)
+IDENTIFIER = Combine(ALPHANUM + ZeroOrMore(IDENTIFIER_END))
+
+NAME = IDENTIFIER("name")
+EXTRA = IDENTIFIER
+
+URI = Regex(r"[^ ]+")("url")
+URL = AT + URI
+
+EXTRAS_LIST = EXTRA + ZeroOrMore(COMMA + EXTRA)
+EXTRAS = (LBRACKET + Optional(EXTRAS_LIST) + RBRACKET)("extras")
+
+VERSION_PEP440 = Regex(Specifier._regex_str, re.VERBOSE | re.IGNORECASE)
+VERSION_LEGACY = Regex(LegacySpecifier._regex_str, re.VERBOSE | re.IGNORECASE)
+
+VERSION_ONE = VERSION_PEP440 ^ VERSION_LEGACY
+VERSION_MANY = Combine(
+    VERSION_ONE + ZeroOrMore(COMMA + VERSION_ONE), joinString=",", adjacent=False
+)("_raw_spec")
+_VERSION_SPEC = Optional((LPAREN + VERSION_MANY + RPAREN) | VERSION_MANY)
+_VERSION_SPEC.setParseAction(lambda s, l, t: t._raw_spec or "")
+
+VERSION_SPEC = originalTextFor(_VERSION_SPEC)("specifier")
+VERSION_SPEC.setParseAction(lambda s, l, t: t[1])
+
+MARKER_EXPR = originalTextFor(MARKER_EXPR())("marker")
+MARKER_EXPR.setParseAction(
+    lambda s, l, t: Marker(s[t._original_start : t._original_end])
+)
+MARKER_SEPARATOR = SEMICOLON
+MARKER = MARKER_SEPARATOR + MARKER_EXPR
+
+VERSION_AND_MARKER = VERSION_SPEC + Optional(MARKER)
+URL_AND_MARKER = URL + Optional(MARKER)
+
+NAMED_REQUIREMENT = NAME + Optional(EXTRAS) + (URL_AND_MARKER | VERSION_AND_MARKER)
+
+REQUIREMENT = stringStart + NAMED_REQUIREMENT + stringEnd
+# pyparsing isn't thread safe during initialization, so we do it eagerly, see
+# issue #104
+REQUIREMENT.parseString("x[]")
+
+
+class Requirement:
+    """Parse a requirement.
+
+    Parse a given requirement string into its parts, such as name, specifier,
+    URL, and extras. Raises InvalidRequirement on a badly-formed requirement
+    string.
+    """
+
+    # TODO: Can we test whether something is contained within a requirement?
+    #       If so how do we do that? Do we need to test against the _name_ of
+    #       the thing as well as the version? What about the markers?
+    # TODO: Can we normalize the name and extra name?
+
+    def __init__(self, requirement_string: str) -> None:
+        try:
+            req = REQUIREMENT.parseString(requirement_string)
+        except ParseException as e:
+            raise InvalidRequirement(
+                f'Parse error at "{ requirement_string[e.loc : e.loc + 8]!r}": {e.msg}'
+            )
+
+        self.name: str = req.name
+        if req.url:
+            parsed_url = urllib.parse.urlparse(req.url)
+            if parsed_url.scheme == "file":
+                if urllib.parse.urlunparse(parsed_url) != req.url:
+                    raise InvalidRequirement("Invalid URL given")
+            elif not (parsed_url.scheme and parsed_url.netloc) or (
+                not parsed_url.scheme and not parsed_url.netloc
+            ):
+                raise InvalidRequirement(f"Invalid URL: {req.url}")
+            self.url: TOptional[str] = req.url
+        else:
+            self.url = None
+        self.extras: Set[str] = set(req.extras.asList() if req.extras else [])
+        self.specifier: SpecifierSet = SpecifierSet(req.specifier)
+        self.marker: TOptional[Marker] = req.marker if req.marker else None
+
+    def __str__(self) -> str:
+        parts: List[str] = [self.name]
+
+        if self.extras:
+            formatted_extras = ",".join(sorted(self.extras))
+            parts.append(f"[{formatted_extras}]")
+
+        if self.specifier:
+            parts.append(str(self.specifier))
+
+        if self.url:
+            parts.append(f"@ {self.url}")
+            if self.marker:
+                parts.append(" ")
+
+        if self.marker:
+            parts.append(f"; {self.marker}")
+
+        return "".join(parts)
+
+    def __repr__(self) -> str:
+        return f"<Requirement('{self}')>"