Consume the PyTest Subsystem to stabilize the pytest version. (pantsb…

…uild#7193)

### Problem

Master is currently broken with python 2 due to a floating pytest version resulting in a lovely new Py2k warning overnight.

### Solution

Pin the v2 pytest runner to the pytest requirement string(s) provided by the `PyTest` `Subsystem`.

### Result

Less-floaty pytest versions.

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

@@ -8,7 +8,7 @@
 from pants.backend.python.python_artifact import PythonArtifact
 from pants.backend.python.python_requirement import PythonRequirement
 from pants.backend.python.python_requirements import PythonRequirements
-from pants.backend.python.rules.python_test_runner import run_python_test
+from pants.backend.python.rules import python_test_runner
 from pants.backend.python.targets.python_app import PythonApp
 from pants.backend.python.targets.python_binary import PythonBinary
 from pants.backend.python.targets.python_distribution import PythonDistribution
@@ -81,4 +81,4 @@ def register_goals():
 
 
 def rules():
-  return (run_python_test,)
+  return tuple(python_test_runner.rules())

src/python/pants/backend/python/rules/BUILD

@@ -1 +1,11 @@
-python_library()
+python_library(
+  dependencies=[
+    'src/python/pants/backend/python/subsystems',
+    'src/python/pants/engine/legacy:graph',
+    'src/python/pants/engine:fs',
+    'src/python/pants/engine:isolated_process',
+    'src/python/pants/engine:rules',
+    'src/python/pants/engine:selectors',
+    'src/python/pants/rules/core',
+  ],
+)

src/python/pants/backend/python/rules/python_test_runner.py

@@ -8,11 +8,12 @@
 import sys
 from builtins import str
 
+from pants.backend.python.subsystems.pytest import PyTest
 from pants.engine.fs import Digest, MergedDirectories, Snapshot, UrlToFetch
 from pants.engine.isolated_process import (ExecuteProcessRequest, ExecuteProcessResult,
                                            FallibleExecuteProcessResult)
 from pants.engine.legacy.graph import TransitiveHydratedTarget
-from pants.engine.rules import rule
+from pants.engine.rules import optionable_rule, rule
 from pants.engine.selectors import Get, Select
 from pants.rules.core.core_test_model import Status, TestResult
 
@@ -26,8 +27,8 @@ class PyTestResult(TestResult):
 
 # TODO: Support deps
 # TODO: Support resources
-@rule(PyTestResult, [Select(TransitiveHydratedTarget)])
-def run_python_test(transitive_hydrated_target):
+@rule(PyTestResult, [Select(TransitiveHydratedTarget), Select(PyTest)])
+def run_python_test(transitive_hydrated_target, pytest):
   target_root = transitive_hydrated_target.root
 
   # TODO: Inject versions and digests here through some option, rather than hard-coding it.
@@ -59,17 +60,16 @@ def run_python_test(transitive_hydrated_target):
   # TODO: This should be configurable, both with interpreter constraints, and for remote execution.
   python_binary = sys.executable
 
+  # TODO: This is non-hermetic because the requirements will be resolved on the fly by
+  # pex27, where it should be hermetically provided in some way.
   output_pytest_requirements_pex_filename = 'pytest-with-requirements.pex'
   requirements_pex_argv = [
     './{}'.format(pex_snapshot.files[0].path),
     '--python', python_binary,
     '-e', 'pytest:main',
     '-o', output_pytest_requirements_pex_filename,
-    # TODO: This is non-hermetic because pytest will be resolved on the fly by pex27, where it should be hermetically provided in some way.
-    # We should probably also specify a specific version.
-    'pytest',
-    # Sort all the requirement strings to increase the chance of cache hits across invocations.
-  ] + sorted(all_requirements)
+    # Sort all user requirement strings to increase the chance of cache hits across invocations.
+  ] + list(pytest.get_requirement_strings()) + sorted(all_requirements)
   requirements_pex_request = ExecuteProcessRequest(
     argv=tuple(requirements_pex_argv),
     input_files=pex_snapshot.directory_digest,
@@ -112,3 +112,10 @@ def run_python_test(transitive_hydrated_target):
   status = Status.SUCCESS if result.exit_code == 0 else Status.FAILURE
 
   yield PyTestResult(status=status, stdout=result.stdout.decode('utf-8'))
+
+
+def rules():
+  return [
+      run_python_test,
+      optionable_rule(PyTest),
+    ]

src/python/pants/init/engine_initializer.py

@@ -10,7 +10,7 @@
 from pants.backend.docgen.targets.doc import Page
 from pants.backend.jvm.targets.jvm_app import JvmApp
 from pants.backend.jvm.targets.jvm_binary import JvmBinary
-from pants.backend.python.rules.python_test_runner import run_python_test
+from pants.backend.python.rules import python_test_runner
 from pants.backend.python.targets.python_app import PythonApp
 from pants.backend.python.targets.python_binary import PythonBinary
 from pants.backend.python.targets.python_library import PythonLibrary
@@ -356,7 +356,7 @@ def setup_legacy_graph_extended(
       create_graph_rules(address_mapper) +
       create_options_parsing_rules() +
       # TODO: This should happen automatically, but most tests (e.g. tests/python/pants_test/auth) fail if it's not here:
-      [run_python_test] +
+      python_test_runner.rules() +
       rules
     )
 

tests/python/pants_test/rules/test_test_integration.py

@@ -71,6 +71,7 @@ def test_passing_python_test(self):
 ============================= test session starts ==============================
 platform SOME_TEXT
 rootdir: SOME_TEXT
+plugins: SOME_TEXT
 collected 1 item
 
 testprojects/tests/python/pants/dummies/test_pass.py .                   [100%]
@@ -90,6 +91,7 @@ def test_failing_python_test(self):
 ============================= test session starts ==============================
 platform SOME_TEXT
 rootdir: SOME_TEXT
+plugins: SOME_TEXT
 collected 1 item
 
 testprojects/tests/python/pants/dummies/test_fail.py F                   [100%]
@@ -117,6 +119,7 @@ def test_source_dep(self):
 ============================= test session starts ==============================
 platform SOME_TEXT
 rootdir: SOME_TEXT
+plugins: SOME_TEXT
 collected 1 item
 
 testprojects/tests/python/pants/dummies/test_with_source_dep.py .        [100%]
@@ -135,6 +138,7 @@ def test_thirdparty_dep(self):
 ============================= test session starts ==============================
 platform SOME_TEXT
 rootdir: SOME_TEXT
+plugins: SOME_TEXT
 collected 1 item
 
 testprojects/tests/python/pants/dummies/test_with_thirdparty_dep.py .    [100%]
@@ -155,6 +159,7 @@ def test_mixed_python_tests(self):
 ============================= test session starts ==============================
 platform SOME_TEXT
 rootdir: SOME_TEXT
+plugins: SOME_TEXT
 collected 1 item
 
 testprojects/tests/python/pants/dummies/test_fail.py F                   [100%]
@@ -171,6 +176,7 @@ def test_fail():
 ============================= test session starts ==============================
 platform SOME_TEXT
 rootdir: SOME_TEXT
+plugins: SOME_TEXT
 collected 1 item
 
 testprojects/tests/python/pants/dummies/test_pass.py .                   [100%]