Add the ability for Pants to provide Python via a union (with a pyenv impl)

src/python/pants/backend/adhoc/adhoc_tool.py

@@ -136,6 +136,7 @@ async def run_in_sandbox_request(
             )
         )
 
+    print(extra_sandbox_contents)
     merged_extras = await Get(
         ExtraSandboxContents, MergeExtraSandboxContents(tuple(extra_sandbox_contents))
     )

src/python/pants/backend/experimental/adhoc/adhoc_tool_backend_integration_test.py

@@ -37,8 +37,10 @@ def test_adhoc_tool_is_loaded_by_backend() -> None:
         args = [
             "--backend-packages=['pants.backend.experimental.adhoc', 'pants.backend.python']",
             f"--source-root-patterns=['{tmpdir}/src']",
+            "--print-stacktrace",
             "package",
             f"{tmpdir}/src:archive",
         ]
         result = run_pants(args)
+        print(result.stdout.strip())
         assert "[INFO] I'm Fleegan Floop!" in result.stderr.strip()

src/python/pants/backend/python/dependency_inference/parse_python_dependencies.py

@@ -192,6 +192,7 @@ async def parse_python_dependencies(
                 file,
             ],
             input_digest=input_digest,
+            append_only_caches=python_interpreter.append_only_caches,
             description=f"Determine Python dependencies for {request.source.address}",
             env=parser_script.env,
             level=LogLevel.DEBUG,

src/python/pants/backend/python/goals/run_helper.py

@@ -27,6 +27,7 @@
 from pants.engine.fs import CreateDigest, Digest, FileContent, MergeDigests
 from pants.engine.rules import Get, MultiGet
 from pants.engine.target import TransitiveTargets, TransitiveTargetsRequest
+from pants.util.frozendict import FrozenDict
 
 
 def _in_chroot(relpath: str) -> str:
@@ -112,12 +113,18 @@ async def _create_python_source_run_request(
         **complete_pex_environment.environment_dict(python_configured=venv_pex.python is not None),
         "PEX_EXTRA_SYS_PATH": os.pathsep.join(source_roots),
     }
+    append_only_caches = (
+        FrozenDict({}) if venv_pex.append_only_caches is None else venv_pex.append_only_caches
+    )
 
     return RunRequest(
         digest=merged_digest,
         args=[_in_chroot(venv_pex.pex.argv0)],
         extra_env=extra_env,
-        append_only_caches=complete_pex_environment.append_only_caches,
+        append_only_caches={
+            **complete_pex_environment.append_only_caches,
+            **append_only_caches,
+        },
     )
 
 

src/python/pants/backend/python/providers/BUILD

@@ -0,0 +1,4 @@
+# Copyright 2023 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+python_sources()

src/python/pants/backend/python/providers/pyenv/BUILD

@@ -0,0 +1,12 @@
+# Copyright 2023 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+python_sources()
+python_tests(
+    name="tests",
+    overrides={
+        "rules_integration_test.py": {
+            "timeout": 600,
+        }
+    },
+)

src/python/pants/backend/python/providers/pyenv/register.py

@@ -0,0 +1,14 @@
+# Copyright 2023 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+
+from pants.backend.python.providers.pyenv.rules import rules as pyenv_rules
+from pants.backend.python.providers.pyenv.target_types import PyenvInstall
+
+
+def target_types():
+    return [PyenvInstall]
+
+
+def rules():
+    return pyenv_rules()