Expose --resolver-version, deprecate --cache-ttl. (#11349)

Update to the new and deprecated features of Pex 2.1.24 by exposing
--resolver-version and deprecating --cache-ttl. For now we keep the
pip-legacy-resolver default for --resolver-version, but encourage users
migrating to the pip-2020-resolver.

pants.toml

@@ -61,6 +61,7 @@ root_patterns = [
 ]
 
 [python-setup]
+resolver_version = "pip-2020-resolver"
 requirement_constraints = "3rdparty/python/constraints.txt"
 resolve_all_constraints = "nondeployables"
 interpreter_constraints = [">=3.7,<3.9"]

src/python/pants/backend/python/lint/flake8/subsystem.py

@@ -12,7 +12,10 @@ class Flake8(PythonToolBase):
 
     options_scope = "flake8"
     default_version = "flake8>=3.7.9,<3.9"
-    default_extra_requirements = ["setuptools<45"]  # NB: `<45` is for Python 2 support
+    default_extra_requirements = [
+        "setuptools<45; python_full_version == '2.7.*'",
+        "setuptools; python_version > '2.7'",
+    ]
     default_entry_point = "flake8"
 
     @classmethod

src/python/pants/backend/python/util_rules/pex.py

@@ -497,8 +497,8 @@ async def create_pex(
         "--no-pypi",
         *(f"--index={index}" for index in python_repos.indexes),
         *(f"--repo={repo}" for repo in python_repos.repos),
-        "--cache-ttl",
-        str(python_setup.resolver_http_cache_ttl),
+        "--resolver-version",
+        python_setup.resolver_version.value,
         *request.additional_args,
     ]
 

src/python/pants/python/python_setup.py

@@ -37,6 +37,13 @@ class ResolveAllConstraintsOption(Enum):
     ALWAYS = "always"
 
 
+class ResolverVersion(Enum):
+    """The resolver implementation to use when resolving Python requirements."""
+
+    PIP_LEGACY = "pip-legacy-resolver"
+    PIP_2020 = "pip-2020-resolver"
+
+
 class PythonSetup(Subsystem):
     """A Python environment."""
 
@@ -107,6 +114,22 @@ def register_options(cls, register):
                 '* "<PEXRC>", paths in the PEX_PYTHON_PATH variable in /etc/pexrc or ~/.pexrc'
             ),
         )
+        register(
+            "--resolver-version",
+            advanced=True,
+            type=ResolverVersion,
+            default=ResolverVersion.PIP_LEGACY,
+            deprecation_start_version="2.3.0.dev1",
+            removal_version="2.5.0.dev1",
+            removal_hint="",
+            help=(
+                "The resolver implementation to use when resolving Python requirements. Support "
+                f"for the {ResolverVersion.PIP_LEGACY.value!r} will be removed in Pants 2.5; so "
+                f"you're encouraged to start using the {ResolverVersion.PIP_2020.value!r} early. "
+                "For more information on this change see "
+                "https://pip.pypa.io/en/latest/user_guide/#changes-to-the-pip-dependency-resolver-in-20-2-2020"
+            ),
+        )
         register(
             "--resolver-manylinux",
             advanced=True,
@@ -132,13 +155,11 @@ def register_options(cls, register):
         register(
             "--resolver-http-cache-ttl",
             type=int,
-            default=3_600,  # This matches PEX's default.
+            default=0,
             advanced=True,
-            help=(
-                "The maximum time (in seconds) for items in the HTTP cache. When the cache expires,"
-                "the PEX resolver will make network requests to see if new versions of your "
-                "requirements are available."
-            ),
+            removal_version="2.4.0.dev1",
+            removal_hint="Unused.",
+            help="Unused.",
         )
 
     @property
@@ -161,6 +182,10 @@ def resolve_all_constraints_was_set_explicitly(self) -> bool:
     def interpreter_search_paths(self):
         return self.expand_interpreter_search_paths(self.options.interpreter_search_paths)
 
+    @property
+    def resolver_version(self) -> ResolverVersion:
+        return cast(ResolverVersion, self.options.resolver_version)
+
     @property
     def manylinux(self) -> Optional[str]:
         manylinux = cast(Optional[str], self.options.resolver_manylinux)
@@ -172,10 +197,6 @@ def manylinux(self) -> Optional[str]:
     def resolver_jobs(self) -> int:
         return cast(int, self.options.resolver_jobs)
 
-    @property
-    def resolver_http_cache_ttl(self) -> int:
-        return cast(int, self.options.resolver_http_cache_ttl)
-
     @property
     def scratch_dir(self):
         return os.path.join(self.options.pants_workdir, *self.options_scope.split("."))