Ensure the hard-coded execution platform label for a toolchain dependency is copied correctly.

Without this, toolchain dependencies do not get the same execution platform as the original target, and toolchain's exec dependencies are not necessarily executable in the original target's actions.

PiperOrigin-RevId: 538541526
Change-Id: Icdcaa75c84d3a0f3f952aa491026e72ef88be099

Author: katre

src/main/java/com/google/devtools/build/lib/analysis/Dependency.java

@@ -99,13 +99,17 @@ public Dependency build() {
 
     protected abstract ImmutableList<String> getTransitionKeys();
 
+    @Nullable
+    protected abstract Label getExecutionPlatformLabel();
+
     /** Returns a copy of this Builder, with the values the same. */
     public Builder copy() {
       return Dependency.builder()
           .setLabel(getLabel())
           .setConfiguration(getConfiguration())
           .setAspects(getAspects())
-          .setTransitionKeys(getTransitionKeys());
+          .setTransitionKeys(getTransitionKeys())
+          .setExecutionPlatformLabel(getExecutionPlatformLabel());
     }
   }
 

src/test/shell/integration/toolchain_transition_test.sh

@@ -318,13 +318,13 @@ register_toolchains(
 EOF
 }
 
-function write_rule() {
+function write_rules() {
   local pkg="${1}"
   mkdir -p "${pkg}/rule"
   cat > "${pkg}/rule/rule.bzl" <<EOF
 load("//${pkg}/platform:platform.bzl", "ShowPlatformInfo", "describe_platform_info")
 
-def _sample_impl(ctx):
+def _report(ctx):
     toolchain = ctx.toolchains["//${pkg}/toolchain:toolchain_type"]
     message = ctx.attr.message
     exec_platform = describe_platform_info(ctx.attr._exec[ShowPlatformInfo])
@@ -336,6 +336,10 @@ def _sample_impl(ctx):
         output = log,
         content = str,
     )
+    return log
+
+def _sample_impl(ctx):
+    log = _report(ctx)
     return [DefaultInfo(files = depset([log]))]
 
 sample = rule(
@@ -353,6 +357,41 @@ sample = rule(
     toolchains = ["//${pkg}/toolchain:toolchain_type"],
     incompatible_use_toolchain_transition = True,
 )
+
+def _sample_test_impl(ctx):
+    log = _report(ctx)
+    # Write a fake test executable.
+    executable = ctx.actions.declare_file(ctx.label.name)
+    ctx.actions.write(
+        output = executable,
+        content = "\n".join([
+            "#!/usr/bin/env bash",
+            "exit 0",
+        ]),
+        is_executable = True,
+    )
+
+    return [DefaultInfo(
+        executable = executable,
+        files = depset([executable, log]),
+    )]
+
+sample_test = rule(
+    implementation = _sample_test_impl,
+    attrs = {
+        "message": attr.string(),
+        "_exec": attr.label(
+            cfg = "exec",
+            providers = [ShowPlatformInfo],
+            default = Label("//${pkg}/platform")),
+    },
+    outputs = {
+        "log": "%{name}.log",
+    },
+    toolchains = ["//${pkg}/toolchain:toolchain_type"],
+    incompatible_use_toolchain_transition = True,
+    test = True,
+)
 EOF
   cat > "${pkg}/rule/BUILD" <<EOF
 package(default_visibility = ["//visibility:public"])
@@ -365,7 +404,7 @@ function test_toolchain_transition() {
   write_constraints "${pkg}"
   write_platforms "${pkg}"
   write_toolchains "${pkg}"
-  write_rule "${pkg}"
+  write_rules "${pkg}"
 
   mkdir -p "${pkg}"
   cat > "${pkg}/BUILD" <<EOF
@@ -398,6 +437,48 @@ EOF
   expect_log 'extra_lib: message: extra_lib foo, target_dep: target, tool_dep: exec-alpha'
 }
 
+# Regression test for b/284495846.
+# Test rules use the test trimming transition, which means that toolchain
+# dependencies are in a different configuration that the actual parent target,
+# which caused an issue where the execution platform was not correctly forwarded
+# to the toolchain.
+function test_toolchain_transition_test_rule() {
+  local -r pkg="${FUNCNAME[0]}"
+  write_constraints "${pkg}"
+  write_platforms "${pkg}"
+  write_toolchains "${pkg}"
+  write_rules "${pkg}"
+
+  mkdir -p "${pkg}"
+  cat > "${pkg}/BUILD" <<EOF
+package(default_visibility = ["//visibility:public"])
+
+load("//${pkg}/rule:rule.bzl", "sample_test")
+
+# Use a test rul to trigger b/284495846
+sample_test(
+    name = "sample_test",
+    exec_compatible_with = [
+        "//${pkg}/constraint:beta",
+    ],
+    message = "Hello",
+)
+EOF
+
+  bazel build \
+    --platforms="//${pkg}/platform:target" \
+    --host_platform="//${pkg}/platform:host" \
+    --use_target_platform_for_tests \
+     "//${pkg}:sample_test" &> $TEST_log || fail "Build failed"
+
+  # Verify contents of sample_test.log.
+  cat "bazel-bin/${pkg}/sample_test.log" >> $TEST_log
+  # The execution platform should be beta.
+  expect_log 'rule message: "Hello", exec platform: "exec-beta"'
+  # The toolchain should have proper target and exec matching the top target.
+  expect_log 'sample_toolchain: message: beta toolchain, target_dep: target, tool_dep: exec-beta'
+}
+
 # Regression test for https://github.com/bazelbuild/bazel/issues/11993
 # This was causing cquery to not correctly generate ConfiguredTargetKeys for
 # toolchains, leading to the message "Targets were missing from graph"
@@ -406,7 +487,7 @@ function test_toolchain_transition_cquery() {
   write_constraints "${pkg}"
   write_platforms "${pkg}"
   write_toolchains "${pkg}"
-  write_rule "${pkg}"
+  write_rules "${pkg}"
 
   mkdir -p "${pkg}"
   cat > "${pkg}/BUILD" <<EOF