From 507aeaab74df6ba48f6762c99f541196191bcee7 Mon Sep 17 00:00:00 2001
From: jcater <jcater@google.com>
Date: Fri, 16 Apr 2021 06:13:52 -0700
Subject: [PATCH] Re-implement cc_host_toolchain_alias to handle toolchain
 resolution.

PiperOrigin-RevId: 368833358
---
 .../rules/cpp/CcHostToolchainAliasRule.java   | 71 +++++++++++++++----
 .../rules/cpp/CcHostToolchainAliasTest.java   | 26 +++++--
 2 files changed, 79 insertions(+), 18 deletions(-)

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasRule.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasRule.java
index bc737b7ac08b73..2ffc367a811eb6 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasRule.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasRule.java
@@ -14,25 +14,72 @@
 
 package com.google.devtools.build.lib.rules.cpp;
 
+import static com.google.devtools.build.lib.packages.Attribute.attr;
+import static com.google.devtools.build.lib.packages.BuildType.LABEL;
+
+import com.google.devtools.build.lib.actions.MutableActionGraph.ActionConflictException;
+import com.google.devtools.build.lib.analysis.BaseRuleClasses;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.MiddlemanProvider;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.analysis.RuleDefinition;
 import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.analysis.Runfiles;
+import com.google.devtools.build.lib.analysis.RunfilesProvider;
+import com.google.devtools.build.lib.analysis.TemplateVariableInfo;
+import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
 import com.google.devtools.build.lib.analysis.config.HostTransition;
-import com.google.devtools.build.lib.cmdline.Label;
-import com.google.devtools.build.lib.packages.Attribute;
-import com.google.devtools.build.lib.rules.LateBoundAlias.CommonAliasRule;
+import com.google.devtools.build.lib.analysis.platform.ToolchainInfo;
+import com.google.devtools.build.lib.packages.RuleClass;
 
 /** Implementation of the {@code cc_toolchain_alias} rule. */
-public class CcHostToolchainAliasRule extends CommonAliasRule<CppConfiguration> {
+public class CcHostToolchainAliasRule implements RuleDefinition {
 
-  public CcHostToolchainAliasRule() {
-    super(
-        "cc_host_toolchain_alias",
-        CppRuleClasses::ccHostToolchainAttribute,
-        CppConfiguration.class);
+  @Override
+  public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment env) {
+    return builder
+        .requiresConfigurationFragments(CppConfiguration.class)
+        .removeAttribute("licenses")
+        .removeAttribute("distribs")
+        .add(
+            attr("$cc_toolchain_alias", LABEL)
+                .cfg(HostTransition.createFactory())
+                .value(env.getToolsLabel("//tools/cpp:current_cc_toolchain")))
+        .build();
   }
 
   @Override
-  protected Attribute.Builder<Label> makeAttribute(RuleDefinitionEnvironment environment) {
-    Attribute.Builder<Label> builder = super.makeAttribute(environment);
-    return builder.cfg(HostTransition.createFactory());
+  public Metadata getMetadata() {
+    return Metadata.builder()
+        .name("cc_host_toolchain_alias")
+        .ancestors(BaseRuleClasses.NativeBuildRule.class)
+        .factoryClass(CcHostToolchainAlias.class)
+        .build();
+  }
+
+  /** Implementation of cc_host_toolchain_alias. */
+  public static class CcHostToolchainAlias implements RuleConfiguredTargetFactory {
+    @Override
+    public ConfiguredTarget create(RuleContext ruleContext)
+        throws InterruptedException, RuleErrorException, ActionConflictException {
+
+      TransitiveInfoCollection ccToolchainAlias =
+          ruleContext.getPrerequisite("$cc_toolchain_alias");
+      CcToolchainProvider ccToolchainProvider = ccToolchainAlias.get(CcToolchainProvider.PROVIDER);
+      TemplateVariableInfo templateVariableInfo =
+          ccToolchainAlias.get(TemplateVariableInfo.PROVIDER);
+      ToolchainInfo toolchain = ccToolchainAlias.get(ToolchainInfo.PROVIDER);
+
+      return new RuleConfiguredTargetBuilder(ruleContext)
+          .addProvider(RunfilesProvider.simple(Runfiles.EMPTY))
+          .addNativeDeclaredProvider(ccToolchainProvider)
+          .addNativeDeclaredProvider(toolchain)
+          .addNativeDeclaredProvider(templateVariableInfo)
+          .setFilesToBuild(ccToolchainProvider.getAllFiles())
+          .addProvider(new MiddlemanProvider(ccToolchainProvider.getAllFilesMiddleman()))
+          .build();
+    }
   }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasTest.java
index b50eb773dec2d5..00df1e430043c8 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcHostToolchainAliasTest.java
@@ -18,8 +18,6 @@
 
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
 import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
-import com.google.devtools.build.lib.cmdline.Label;
-import com.google.devtools.build.lib.packages.util.MockCcSupport;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -54,7 +52,6 @@ public void testThatHostCrosstoolTopCommandLineArgumentWorks() throws Exception
         "})",
         "cc_toolchain(",
         "    name = 'toolchain_b',",
-        "    toolchain_identifier = 'mock-llvm-toolchain-k8',",
         "    toolchain_config = ':mock_config',",
         "    all_files = ':banana',",
         "    ar_files = ':empty',",
@@ -66,14 +63,31 @@ public void testThatHostCrosstoolTopCommandLineArgumentWorks() throws Exception
         "    objcopy_files = ':empty')",
         "cc_toolchain_config(name='mock_config')");
 
-    scratch.file("b/cc_toolchain_config.bzl", MockCcSupport.EMPTY_CC_TOOLCHAIN);
+    scratch.file(
+        "b/cc_toolchain_config.bzl",
+        "def _impl(ctx):",
+        "    return cc_common.create_cc_toolchain_config_info(",
+        "                ctx = ctx,",
+        "                toolchain_identifier = 'custom_toolchain',",
+        "                host_system_name = 'mock-system-name-for-k8',",
+        "                target_system_name = 'mock-target-system-name-for-k8',",
+        "                target_cpu = 'k8',",
+        "                target_libc = 'mock-libc-for-k8',",
+        "                compiler = 'mock-compiler-for-k8',",
+        "                abi_libc_version = 'mock-abi-libc-for-k8',",
+        "                abi_version = 'mock-abi-version-for-k8')",
+        "cc_toolchain_config = rule(",
+        "    implementation = _impl,",
+        "    attrs = {},",
+        "    provides = [CcToolchainConfigInfo],",
+        ")");
 
     scratch.file("a/BUILD", "cc_host_toolchain_alias(name='current_cc_host_toolchain')");
 
     useConfiguration("--host_crosstool_top=//b:my_custom_toolchain_suite", "--host_cpu=k8");
     ConfiguredTarget target = getConfiguredTarget("//a:current_cc_host_toolchain");
 
-    assertThat(target.getLabel())
-        .isEqualTo(Label.parseAbsoluteUnchecked("//b:my_custom_toolchain_suite"));
+    CcToolchainProvider ccToolchainProvider = target.get(CcToolchainProvider.PROVIDER);
+    assertThat(ccToolchainProvider.getToolchainIdentifier()).isEqualTo("custom_toolchain");
   }
 }