[internal] Introduce OptionalPex/OptionalPexRequest.

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

@@ -66,6 +66,8 @@
 from pants.util.ordered_set import FrozenOrderedSet
 from pants.util.strutil import pluralize
 
+logger = logging.getLogger(__name__)
+
 
 @dataclass(frozen=True)
 class Lockfile:
@@ -255,6 +257,11 @@ def debug_hint(self) -> str:
         return self.output_filename
 
 
+@dataclass(frozen=True)
+class OptionalPexRequest:
+    maybe_pex_request: PexRequest | None
+
+
 @dataclass(frozen=True)
 class Pex:
     """Wrapper for a digest containing a pex file created with some filename."""
@@ -264,7 +271,9 @@ class Pex:
     python: PythonExecutable | None
 
 
-logger = logging.getLogger(__name__)
+@dataclass(frozen=True)
+class OptionalPex:
+    maybe_pex: Pex | None
 
 
 @rule(desc="Find Python interpreter for constraints", level=LogLevel.DEBUG)
@@ -690,6 +699,14 @@ async def create_pex(request: PexRequest) -> Pex:
     return result.create_pex()
 
 
+@rule
+async def create_optional_pex(request: OptionalPexRequest) -> OptionalPex:
+    if request.maybe_pex_request is None:
+        return OptionalPex(None)
+    result = await Get(Pex, PexRequest, request.maybe_pex_request)
+    return OptionalPex(result)
+
+
 @dataclass(frozen=True)
 class Script:
     path: PurePath

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

@@ -23,7 +23,8 @@
 from pants.backend.python.util_rules.local_dists import rules as local_dists_rules
 from pants.backend.python.util_rules.pex import (
     Lockfile,
-    Pex,
+    OptionalPex,
+    OptionalPexRequest,
     PexPlatforms,
     PexRequest,
     PexRequirements,
@@ -230,11 +231,6 @@ async def interpreter_constraints_for_targets(
     return interpreter_constraints
 
 
-@dataclass(frozen=True)
-class _RepositoryPex:
-    maybe_pex: Pex | None
-
-
 @dataclass(frozen=True)
 class _RepositoryPexRequest:
     requirements: PexRequirements
@@ -322,7 +318,7 @@ async def pex_from_targets(request: PexFromTargetsRequest) -> PexRequest:
 
     if requirements:
         repository_pex = await Get(
-            _RepositoryPex,
+            OptionalPex,
             _RepositoryPexRequest(
                 requirements,
                 request.platforms,
@@ -351,15 +347,14 @@ async def pex_from_targets(request: PexFromTargetsRequest) -> PexRequest:
 @rule
 async def get_repository_pex(
     request: _RepositoryPexRequest, python_setup: PythonSetup
-) -> _RepositoryPex:
-    repository_pex: Pex | None = None
+) -> OptionalPexRequest:
+    repository_pex_request: PexRequest | None = None
     if python_setup.requirement_constraints:
-        maybe_constraints_repository_pex = await Get(
-            _RepositoryPex,
+        constraints_repository_pex_request = await Get(
+            OptionalPexRequest,
             _ConstraintsRepositoryPexRequest(request),
         )
-        if maybe_constraints_repository_pex.maybe_pex:
-            repository_pex = maybe_constraints_repository_pex.maybe_pex
+        repository_pex_request = constraints_repository_pex_request.maybe_pex_request
     elif (
         python_setup.resolve_all_constraints
         and python_setup.resolve_all_constraints_was_set_explicitly()
@@ -370,59 +365,53 @@ async def get_repository_pex(
         )
     elif request.resolve_and_lockfile:
         resolve, lockfile = request.resolve_and_lockfile
-        repository_pex = await Get(
-            Pex,
-            PexRequest(
-                description=f"Installing {lockfile} for the resolve `{resolve}`",
-                output_filename=f"{path_safe(resolve)}_lockfile.pex",
-                internal_only=request.internal_only,
-                requirements=Lockfile(
-                    file_path=lockfile,
-                    file_path_description_of_origin=(
-                        f"the resolve `{resolve}` (from "
-                        "`[python].experimental_resolves_to_lockfiles`)"
-                    ),
-                    # TODO(#12314): Hook up lockfile staleness check.
-                    lockfile_hex_digest=None,
-                    req_strings=None,
+        repository_pex_request = PexRequest(
+            description=f"Installing {lockfile} for the resolve `{resolve}`",
+            output_filename=f"{path_safe(resolve)}_lockfile.pex",
+            internal_only=request.internal_only,
+            requirements=Lockfile(
+                file_path=lockfile,
+                file_path_description_of_origin=(
+                    f"the resolve `{resolve}` (from "
+                    "`[python].experimental_resolves_to_lockfiles`)"
                 ),
-                interpreter_constraints=request.interpreter_constraints,
-                platforms=request.platforms,
-                additional_args=request.additional_lockfile_args,
+                # TODO(#12314): Hook up lockfile staleness check.
+                lockfile_hex_digest=None,
+                req_strings=None,
             ),
+            interpreter_constraints=request.interpreter_constraints,
+            platforms=request.platforms,
+            additional_args=request.additional_lockfile_args,
         )
     elif python_setup.lockfile:
-        repository_pex = await Get(
-            Pex,
-            PexRequest(
-                description=f"Installing {python_setup.lockfile}",
-                output_filename="lockfile.pex",
-                internal_only=request.internal_only,
-                requirements=Lockfile(
-                    file_path=python_setup.lockfile,
-                    file_path_description_of_origin=("the option `[python].experimental_lockfile`"),
-                    # TODO(#12314): Hook up lockfile staleness check once multiple lockfiles
-                    # are supported.
-                    lockfile_hex_digest=None,
-                    req_strings=None,
-                ),
-                interpreter_constraints=request.interpreter_constraints,
-                platforms=request.platforms,
-                additional_args=request.additional_lockfile_args,
+        repository_pex_request = PexRequest(
+            description=f"Installing {python_setup.lockfile}",
+            output_filename="lockfile.pex",
+            internal_only=request.internal_only,
+            requirements=Lockfile(
+                file_path=python_setup.lockfile,
+                file_path_description_of_origin=("the option `[python].experimental_lockfile`"),
+                # TODO(#12314): Hook up lockfile staleness check once multiple lockfiles
+                # are supported.
+                lockfile_hex_digest=None,
+                req_strings=None,
             ),
+            interpreter_constraints=request.interpreter_constraints,
+            platforms=request.platforms,
+            additional_args=request.additional_lockfile_args,
         )
-    return _RepositoryPex(repository_pex)
+    return OptionalPexRequest(repository_pex_request)
 
 
 @rule
 async def _setup_constraints_repository_pex(
     constraints_request: _ConstraintsRepositoryPexRequest, python_setup: PythonSetup
-) -> _RepositoryPex:
+) -> OptionalPexRequest:
     request = constraints_request.repository_pex_request
     # NB: it isn't safe to resolve against the whole constraints file if
     # platforms are in use. See https://github.com/pantsbuild/pants/issues/12222.
     if not python_setup.resolve_all_constraints or request.platforms:
-        return _RepositoryPex(None)
+        return OptionalPexRequest(None)
 
     constraints_path = python_setup.requirement_constraints
     assert constraints_path is not None
@@ -468,7 +457,7 @@ async def _setup_constraints_repository_pex(
             f"entries for the following requirements: {', '.join(unconstrained_projects)}.\n\n"
             f"Ignoring `[python_setup].resolve_all_constraints` option."
         )
-        return _RepositoryPex(None)
+        return OptionalPexRequest(None)
 
     # To get a full set of requirements we must add the URL requirements to the
     # constraints file, since the latter cannot contain URL requirements.
@@ -479,24 +468,21 @@ async def _setup_constraints_repository_pex(
     #  all these repository pexes will have identical pinned versions of everything,
     #  this is not a correctness issue, only a performance one.
     all_constraints = {str(req) for req in (constraints_file_reqs | url_reqs)}
-    repository_pex = await Get(
-        Pex,
-        PexRequest(
-            description=f"Resolving {constraints_path}",
-            output_filename="repository.pex",
-            internal_only=request.internal_only,
-            requirements=PexRequirements(
-                all_constraints,
-                apply_constraints=True,
-                # TODO: See PexRequirements docs.
-                is_all_constraints_resolve=True,
-            ),
-            interpreter_constraints=request.interpreter_constraints,
-            platforms=request.platforms,
-            additional_args=request.additional_lockfile_args,
+    repository_pex = PexRequest(
+        description=f"Resolving {constraints_path}",
+        output_filename="repository.pex",
+        internal_only=request.internal_only,
+        requirements=PexRequirements(
+            all_constraints,
+            apply_constraints=True,
+            # TODO: See PexRequirements docs.
+            is_all_constraints_resolve=True,
         ),
+        interpreter_constraints=request.interpreter_constraints,
+        platforms=request.platforms,
+        additional_args=request.additional_lockfile_args,
     )
-    return _RepositoryPex(repository_pex)
+    return OptionalPexRequest(repository_pex)
 
 
 @frozen_after_init