Add RuleRunner.write_digest() (#13044)

Also use it to improve our test for `go_package` support.

[ci skip-rust]
[ci skip-build-wheels]

src/python/pants/backend/go/goals/package_binary_integration_test.py

@@ -3,6 +3,8 @@
 
 from __future__ import annotations
 
+import os.path
+import subprocess
 from textwrap import dedent
 
 import pytest
@@ -22,9 +24,9 @@
     link,
     sdk,
 )
-from pants.build_graph.address import Address
 from pants.core.goals.package import BuiltPackage
 from pants.core.util_rules import source_files
+from pants.engine.addresses import Address
 from pants.engine.rules import QueryRule
 from pants.engine.target import Target
 from pants.testutil.rule_runner import RuleRunner
@@ -56,7 +58,9 @@ def rule_runner() -> RuleRunner:
 
 def build_package(rule_runner: RuleRunner, binary_target: Target) -> BuiltPackage:
     field_set = GoBinaryFieldSet.create(binary_target)
-    return rule_runner.request(BuiltPackage, [field_set])
+    result = rule_runner.request(BuiltPackage, [field_set])
+    rule_runner.write_digest(result.digest)
+    return result
 
 
 def test_package_simple(rule_runner: RuleRunner) -> None:
@@ -90,6 +94,10 @@ def test_package_simple(rule_runner: RuleRunner) -> None:
     assert len(built_package.artifacts) == 1
     assert built_package.artifacts[0].relpath == "bin"
 
+    result = subprocess.run([os.path.join(rule_runner.build_root, "bin")], stdout=subprocess.PIPE)
+    assert result.returncode == 0
+    assert result.stdout == b"Hello world!\n"
+
 
 def test_package_with_dependency(rule_runner: RuleRunner) -> None:
     rule_runner.write_files(
@@ -136,3 +144,7 @@ def test_package_with_dependency(rule_runner: RuleRunner) -> None:
     built_package = build_package(rule_runner, binary_tgt)
     assert len(built_package.artifacts) == 1
     assert built_package.artifacts[0].relpath == "bin"
+
+    result = subprocess.run([os.path.join(rule_runner.build_root, "bin")], stdout=subprocess.PIPE)
+    assert result.returncode == 0
+    assert result.stdout == b">> Hello world! <<\n"

src/python/pants/testutil/rule_runner.py

@@ -22,8 +22,9 @@
 from pants.engine.addresses import Address
 from pants.engine.console import Console
 from pants.engine.environment import CompleteEnvironment
-from pants.engine.fs import PathGlobs, PathGlobsAndRoot, Snapshot, Workspace
+from pants.engine.fs import Digest, PathGlobs, PathGlobsAndRoot, Snapshot, Workspace
 from pants.engine.goal import Goal
+from pants.engine.internals import native_engine
 from pants.engine.internals.native_engine import PyExecutor
 from pants.engine.internals.scheduler import SchedulerSession
 from pants.engine.internals.selectors import Get, Params
@@ -391,6 +392,15 @@ def get_target(self, address: Address) -> Target:
         """
         return self.request(WrappedTarget, [address]).target
 
+    def write_digest(self, digest: Digest, *, path_prefix: str | None = None) -> None:
+        """Write a digest to disk, relative to the test's build root.
+
+        Access the written files by using `os.path.join(rule_runner.build_root, <relpath>)`.
+        """
+        native_engine.write_digest(
+            self.scheduler.py_scheduler, self.scheduler.py_session, digest, path_prefix or ""
+        )
+
 
 # -----------------------------------------------------------------------------------------------
 # `run_rule_with_mocks()`