prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  New resolver cannot installs distributions that only have pre releases
  **Environment**
  
  * pip version: master, today
  * Python version: 3
  * OS: linux
  
  **Description**
  
  I want to install a distribution that only has pre-releases. The legacy resolver does support this. The new one does not. 
  
  Note: using `--pre` does not seem to influence the result. The legacy resolver could install such distributions without using `--pre`.
  
  **Expected behavior**
  
  Installation should succeed.
  
  **How to Reproduce**
  
  ```console
  $ pip install --no-deps odoo13-addon-date-range --unstable-feature=resolver
  ERROR: Exception:
  Traceback (most recent call last):
    File "/home/me/pip/src/pip/_internal/cli/base_command.py", line 199, in _main
      status = self.run(options, args)
    File "/home/me/pip/src/pip/_internal/cli/req_command.py", line 185, in wrapper
      return func(self, options, args)
    File "/home/me/pip/src/pip/_internal/commands/install.py", line 333, in run
      reqs, check_supported_wheels=not options.target_dir
    File "/home/me/pip/src/pip/_internal/resolution/resolvelib/resolver.py", line 80, in resolve
      self._result = resolver.resolve(requirements)
    File "/home/me/pip/src/pip/_vendor/resolvelib/resolvers.py", line 413, in resolve
      state = resolution.resolve(requirements, max_rounds=max_rounds)
    File "/home/me/pip/src/pip/_vendor/resolvelib/resolvers.py", line 310, in resolve
      failure_causes = self._attempt_to_pin_criterion(name, criterion)
    File "/home/me/pip/src/pip/_vendor/resolvelib/resolvers.py", line 240, in _attempt_to_pin_criterion
      raise InconsistentCandidate(candidate, criterion)
  pip._vendor.resolvelib.resolvers.InconsistentCandidate: Provided candidate LinkCandidate('https://files.pythonhosted.org/packages/1f/0b/945335a37082b6b013cc1331f49e3f5b6a18cdd0b693475e6ca9e9a7df6e/odoo13_addon_date_range-13.0.1.0.1.dev8-py3-none-any.whl#sha256=3883bbe87db8d5db4364e8a42e86546e19e8e4f123d98c4e9454587dfa9401df (from https://pypi.org/simple/odoo13-addon-date-range/) (requires-python:>=3.5)') does not satisfy SpecifierRequirement('odoo13-addon-date-range')
  ```
  
  Note I used `--no-deps` because a dependency is not on pypi, but that has no influence on the result.
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `src/pip/_internal/resolution/resolvelib/requirements.py`
  Content:
  ```
  1 from pip._vendor.packaging.utils import canonicalize_name
  2 
  3 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
  4 
  5 from .base import Requirement, format_name
  6 
  7 if MYPY_CHECK_RUNNING:
  8     from typing import Sequence
  9 
  10     from pip._vendor.packaging.specifiers import SpecifierSet
  11 
  12     from pip._internal.req.req_install import InstallRequirement
  13 
  14     from .base import Candidate
  15     from .factory import Factory
  16 
  17 
  18 class ExplicitRequirement(Requirement):
  19     def __init__(self, candidate):
  20         # type: (Candidate) -> None
  21         self.candidate = candidate
  22 
  23     def __repr__(self):
  24         # type: () -> str
  25         return "{class_name}({candidate!r})".format(
  26             class_name=self.__class__.__name__,
  27             candidate=self.candidate,
  28         )
  29 
  30     @property
  31     def name(self):
  32         # type: () -> str
  33         # No need to canonicalise - the candidate did this
  34         return self.candidate.name
  35 
  36     def find_matches(self):
  37         # type: () -> Sequence[Candidate]
  38         return [self.candidate]
  39 
  40     def is_satisfied_by(self, candidate):
  41         # type: (Candidate) -> bool
  42         return candidate == self.candidate
  43 
  44 
  45 class SpecifierRequirement(Requirement):
  46     def __init__(self, ireq, factory):
  47         # type: (InstallRequirement, Factory) -> None
  48         assert ireq.link is None, "This is a link, not a specifier"
  49         self._ireq = ireq
  50         self._factory = factory
  51         self.extras = ireq.req.extras
  52 
  53     def __str__(self):
  54         # type: () -> str
  55         return str(self._ireq.req)
  56 
  57     def __repr__(self):
  58         # type: () -> str
  59         return "{class_name}({requirement!r})".format(
  60             class_name=self.__class__.__name__,
  61             requirement=str(self._ireq.req),
  62         )
  63 
  64     @property
  65     def name(self):
  66         # type: () -> str
  67         canonical_name = canonicalize_name(self._ireq.req.name)
  68         return format_name(canonical_name, self.extras)
  69 
  70     def find_matches(self):
  71         # type: () -> Sequence[Candidate]
  72         it = self._factory.iter_found_candidates(self._ireq, self.extras)
  73         return list(it)
  74 
  75     def is_satisfied_by(self, candidate):
  76         # type: (Candidate) -> bool
  77         assert candidate.name == self.name, \
  78             "Internal issue: Candidate is not for this requirement " \
  79             " {} vs {}".format(candidate.name, self.name)
  80         return candidate.version in self._ireq.req.specifier
  81 
  82 
  83 class RequiresPythonRequirement(Requirement):
  84     """A requirement representing Requires-Python metadata.
  85     """
  86     def __init__(self, specifier, match):
  87         # type: (SpecifierSet, Candidate) -> None
  88         self.specifier = specifier
  89         self._candidate = match
  90 
  91     def __repr__(self):
  92         # type: () -> str
  93         return "{class_name}({specifier!r})".format(
  94             class_name=self.__class__.__name__,
  95             specifier=str(self.specifier),
  96         )
  97 
  98     @property
  99     def name(self):
  100         # type: () -> str
  101         return self._candidate.name
  102 
  103     def find_matches(self):
  104         # type: () -> Sequence[Candidate]
  105         if self._candidate.version in self.specifier:
  106             return [self._candidate]
  107         return []
  108 
  109     def is_satisfied_by(self, candidate):
  110         # type: (Candidate) -> bool
  111         assert candidate.name == self._candidate.name, "Not Python candidate"
  112         return candidate.version in self.specifier
  113
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/src/pip/_internal/resolution/resolvelib/requirements.py b/src/pip/_internal/resolution/resolvelib/requirements.py
  --- a/src/pip/_internal/resolution/resolvelib/requirements.py
  +++ b/src/pip/_internal/resolution/resolvelib/requirements.py
  @@ -77,7 +77,11 @@
           assert candidate.name == self.name, \
               "Internal issue: Candidate is not for this requirement " \
               " {} vs {}".format(candidate.name, self.name)
  -        return candidate.version in self._ireq.req.specifier
  +        # We can safely always allow prereleases here since PackageFinder
  +        # already implements the prerelease logic, and would have filtered out
  +        # prerelease candidates if the user does not expect them.
  +        spec = self._ireq.req.specifier
  +        return spec.contains(candidate.version, prereleases=True)
   
   
   class RequiresPythonRequirement(Requirement):
  @@ -109,4 +113,7 @@
       def is_satisfied_by(self, candidate):
           # type: (Candidate) -> bool
           assert candidate.name == self._candidate.name, "Not Python candidate"
  -        return candidate.version in self.specifier
  +        # We can safely always allow prereleases here since PackageFinder
  +        # already implements the prerelease logic, and would have filtered out
  +        # prerelease candidates if the user does not expect them.
  +        return self.specifier.contains(candidate.version, prereleases=True)
  
verification_info: {"golden_diff": "diff --git a/src/pip/_internal/resolution/resolvelib/requirements.py b/src/pip/_internal/resolution/resolvelib/requirements.py\n--- a/src/pip/_internal/resolution/resolvelib/requirements.py\n+++ b/src/pip/_internal/resolution/resolvelib/requirements.py\n@@ -77,7 +77,11 @@\n         assert candidate.name == self.name, \\\n             \"Internal issue: Candidate is not for this requirement \" \\\n             \" {} vs {}\".format(candidate.name, self.name)\n-        return candidate.version in self._ireq.req.specifier\n+        # We can safely always allow prereleases here since PackageFinder\n+        # already implements the prerelease logic, and would have filtered out\n+        # prerelease candidates if the user does not expect them.\n+        spec = self._ireq.req.specifier\n+        return spec.contains(candidate.version, prereleases=True)\n \n \n class RequiresPythonRequirement(Requirement):\n@@ -109,4 +113,7 @@\n     def is_satisfied_by(self, candidate):\n         # type: (Candidate) -> bool\n         assert candidate.name == self._candidate.name, \"Not Python candidate\"\n-        return candidate.version in self.specifier\n+        # We can safely always allow prereleases here since PackageFinder\n+        # already implements the prerelease logic, and would have filtered out\n+        # prerelease candidates if the user does not expect them.\n+        return self.specifier.contains(candidate.version, prereleases=True)\n", "issue": "New resolver cannot installs distributions that only have pre releases\n**Environment**\r\n\r\n* pip version: master, today\r\n* Python version: 3\r\n* OS: linux\r\n\r\n**Description**\r\n\r\nI want to install a distribution that only has pre-releases. The legacy resolver does support this. The new one does not. \r\n\r\nNote: using `--pre` does not seem to influence the result. The legacy resolver could install such distributions without using `--pre`.\r\n\r\n**Expected behavior**\r\n\r\nInstallation should succeed.\r\n\r\n**How to Reproduce**\r\n\r\n```console\r\n$ pip install --no-deps odoo13-addon-date-range --unstable-feature=resolver\r\nERROR: Exception:\r\nTraceback (most recent call last):\r\n  File \"/home/me/pip/src/pip/_internal/cli/base_command.py\", line 199, in _main\r\n    status = self.run(options, args)\r\n  File \"/home/me/pip/src/pip/_internal/cli/req_command.py\", line 185, in wrapper\r\n    return func(self, options, args)\r\n  File \"/home/me/pip/src/pip/_internal/commands/install.py\", line 333, in run\r\n    reqs, check_supported_wheels=not options.target_dir\r\n  File \"/home/me/pip/src/pip/_internal/resolution/resolvelib/resolver.py\", line 80, in resolve\r\n    self._result = resolver.resolve(requirements)\r\n  File \"/home/me/pip/src/pip/_vendor/resolvelib/resolvers.py\", line 413, in resolve\r\n    state = resolution.resolve(requirements, max_rounds=max_rounds)\r\n  File \"/home/me/pip/src/pip/_vendor/resolvelib/resolvers.py\", line 310, in resolve\r\n    failure_causes = self._attempt_to_pin_criterion(name, criterion)\r\n  File \"/home/me/pip/src/pip/_vendor/resolvelib/resolvers.py\", line 240, in _attempt_to_pin_criterion\r\n    raise InconsistentCandidate(candidate, criterion)\r\npip._vendor.resolvelib.resolvers.InconsistentCandidate: Provided candidate LinkCandidate('https://files.pythonhosted.org/packages/1f/0b/945335a37082b6b013cc1331f49e3f5b6a18cdd0b693475e6ca9e9a7df6e/odoo13_addon_date_range-13.0.1.0.1.dev8-py3-none-any.whl#sha256=3883bbe87db8d5db4364e8a42e86546e19e8e4f123d98c4e9454587dfa9401df (from https://pypi.org/simple/odoo13-addon-date-range/) (requires-python:>=3.5)') does not satisfy SpecifierRequirement('odoo13-addon-date-range')\r\n```\r\n\r\nNote I used `--no-deps` because a dependency is not on pypi, but that has no influence on the result.\n", "before_files": [{"content": "from pip._vendor.packaging.utils import canonicalize_name\n\nfrom pip._internal.utils.typing import MYPY_CHECK_RUNNING\n\nfrom .base import Requirement, format_name\n\nif MYPY_CHECK_RUNNING:\n    from typing import Sequence\n\n    from pip._vendor.packaging.specifiers import SpecifierSet\n\n    from pip._internal.req.req_install import InstallRequirement\n\n    from .base import Candidate\n    from .factory import Factory\n\n\nclass ExplicitRequirement(Requirement):\n    def __init__(self, candidate):\n        # type: (Candidate) -> None\n        self.candidate = candidate\n\n    def __repr__(self):\n        # type: () -> str\n        return \"{class_name}({candidate!r})\".format(\n            class_name=self.__class__.__name__,\n            candidate=self.candidate,\n        )\n\n    @property\n    def name(self):\n        # type: () -> str\n        # No need to canonicalise - the candidate did this\n        return self.candidate.name\n\n    def find_matches(self):\n        # type: () -> Sequence[Candidate]\n        return [self.candidate]\n\n    def is_satisfied_by(self, candidate):\n        # type: (Candidate) -> bool\n        return candidate == self.candidate\n\n\nclass SpecifierRequirement(Requirement):\n    def __init__(self, ireq, factory):\n        # type: (InstallRequirement, Factory) -> None\n        assert ireq.link is None, \"This is a link, not a specifier\"\n        self._ireq = ireq\n        self._factory = factory\n        self.extras = ireq.req.extras\n\n    def __str__(self):\n        # type: () -> str\n        return str(self._ireq.req)\n\n    def __repr__(self):\n        # type: () -> str\n        return \"{class_name}({requirement!r})\".format(\n            class_name=self.__class__.__name__,\n            requirement=str(self._ireq.req),\n        )\n\n    @property\n    def name(self):\n        # type: () -> str\n        canonical_name = canonicalize_name(self._ireq.req.name)\n        return format_name(canonical_name, self.extras)\n\n    def find_matches(self):\n        # type: () -> Sequence[Candidate]\n        it = self._factory.iter_found_candidates(self._ireq, self.extras)\n        return list(it)\n\n    def is_satisfied_by(self, candidate):\n        # type: (Candidate) -> bool\n        assert candidate.name == self.name, \\\n            \"Internal issue: Candidate is not for this requirement \" \\\n            \" {} vs {}\".format(candidate.name, self.name)\n        return candidate.version in self._ireq.req.specifier\n\n\nclass RequiresPythonRequirement(Requirement):\n    \"\"\"A requirement representing Requires-Python metadata.\n    \"\"\"\n    def __init__(self, specifier, match):\n        # type: (SpecifierSet, Candidate) -> None\n        self.specifier = specifier\n        self._candidate = match\n\n    def __repr__(self):\n        # type: () -> str\n        return \"{class_name}({specifier!r})\".format(\n            class_name=self.__class__.__name__,\n            specifier=str(self.specifier),\n        )\n\n    @property\n    def name(self):\n        # type: () -> str\n        return self._candidate.name\n\n    def find_matches(self):\n        # type: () -> Sequence[Candidate]\n        if self._candidate.version in self.specifier:\n            return [self._candidate]\n        return []\n\n    def is_satisfied_by(self, candidate):\n        # type: (Candidate) -> bool\n        assert candidate.name == self._candidate.name, \"Not Python candidate\"\n        return candidate.version in self.specifier\n", "path": "src/pip/_internal/resolution/resolvelib/requirements.py"}], "after_files": [{"content": "from pip._vendor.packaging.utils import canonicalize_name\n\nfrom pip._internal.utils.typing import MYPY_CHECK_RUNNING\n\nfrom .base import Requirement, format_name\n\nif MYPY_CHECK_RUNNING:\n    from typing import Sequence\n\n    from pip._vendor.packaging.specifiers import SpecifierSet\n\n    from pip._internal.req.req_install import InstallRequirement\n\n    from .base import Candidate\n    from .factory import Factory\n\n\nclass ExplicitRequirement(Requirement):\n    def __init__(self, candidate):\n        # type: (Candidate) -> None\n        self.candidate = candidate\n\n    def __repr__(self):\n        # type: () -> str\n        return \"{class_name}({candidate!r})\".format(\n            class_name=self.__class__.__name__,\n            candidate=self.candidate,\n        )\n\n    @property\n    def name(self):\n        # type: () -> str\n        # No need to canonicalise - the candidate did this\n        return self.candidate.name\n\n    def find_matches(self):\n        # type: () -> Sequence[Candidate]\n        return [self.candidate]\n\n    def is_satisfied_by(self, candidate):\n        # type: (Candidate) -> bool\n        return candidate == self.candidate\n\n\nclass SpecifierRequirement(Requirement):\n    def __init__(self, ireq, factory):\n        # type: (InstallRequirement, Factory) -> None\n        assert ireq.link is None, \"This is a link, not a specifier\"\n        self._ireq = ireq\n        self._factory = factory\n        self.extras = ireq.req.extras\n\n    def __str__(self):\n        # type: () -> str\n        return str(self._ireq.req)\n\n    def __repr__(self):\n        # type: () -> str\n        return \"{class_name}({requirement!r})\".format(\n            class_name=self.__class__.__name__,\n            requirement=str(self._ireq.req),\n        )\n\n    @property\n    def name(self):\n        # type: () -> str\n        canonical_name = canonicalize_name(self._ireq.req.name)\n        return format_name(canonical_name, self.extras)\n\n    def find_matches(self):\n        # type: () -> Sequence[Candidate]\n        it = self._factory.iter_found_candidates(self._ireq, self.extras)\n        return list(it)\n\n    def is_satisfied_by(self, candidate):\n        # type: (Candidate) -> bool\n        assert candidate.name == self.name, \\\n            \"Internal issue: Candidate is not for this requirement \" \\\n            \" {} vs {}\".format(candidate.name, self.name)\n        # We can safely always allow prereleases here since PackageFinder\n        # already implements the prerelease logic, and would have filtered out\n        # prerelease candidates if the user does not expect them.\n        spec = self._ireq.req.specifier\n        return spec.contains(candidate.version, prereleases=True)\n\n\nclass RequiresPythonRequirement(Requirement):\n    \"\"\"A requirement representing Requires-Python metadata.\n    \"\"\"\n    def __init__(self, specifier, match):\n        # type: (SpecifierSet, Candidate) -> None\n        self.specifier = specifier\n        self._candidate = match\n\n    def __repr__(self):\n        # type: () -> str\n        return \"{class_name}({specifier!r})\".format(\n            class_name=self.__class__.__name__,\n            specifier=str(self.specifier),\n        )\n\n    @property\n    def name(self):\n        # type: () -> str\n        return self._candidate.name\n\n    def find_matches(self):\n        # type: () -> Sequence[Candidate]\n        if self._candidate.version in self.specifier:\n            return [self._candidate]\n        return []\n\n    def is_satisfied_by(self, candidate):\n        # type: (Candidate) -> bool\n        assert candidate.name == self._candidate.name, \"Not Python candidate\"\n        # We can safely always allow prereleases here since PackageFinder\n        # already implements the prerelease logic, and would have filtered out\n        # prerelease candidates if the user does not expect them.\n        return self.specifier.contains(candidate.version, prereleases=True)\n", "path": "src/pip/_internal/resolution/resolvelib/requirements.py"}]}