From 272b1bf6b91bb7ac93e985d5248ee6411ae20a14 Mon Sep 17 00:00:00 2001
From: Bart Staal <bart.staal@gmail.com>
Date: Thu, 25 Feb 2021 00:34:41 +0100
Subject: [PATCH] Support contraint_values in select()s for alias rules

Fixes #13047
---
 .../devtools/build/lib/rules/Alias.java       |  4 --
 .../analysis/ConfigurableAttributesTest.java  | 39 +++++++++++++++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/src/main/java/com/google/devtools/build/lib/rules/Alias.java b/src/main/java/com/google/devtools/build/lib/rules/Alias.java
index d50fa98e99caa6..b916124c8cf401 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/Alias.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/Alias.java
@@ -89,10 +89,6 @@ public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment envi
                   .allowedRuleClasses(ANY_RULE)
                   .mandatory())
           .canHaveAnyProvider()
-          // Aliases themselves do not need toolchains or an execution platform, so this is fine.
-          // The actual target will resolve platforms and toolchains with no issues regardless of
-          // this setting.
-          .useToolchainResolution(false)
           .build();
     }
 
diff --git a/src/test/java/com/google/devtools/build/lib/analysis/ConfigurableAttributesTest.java b/src/test/java/com/google/devtools/build/lib/analysis/ConfigurableAttributesTest.java
index 4cd7ad34d9424d..070a7f9b5d4179 100644
--- a/src/test/java/com/google/devtools/build/lib/analysis/ConfigurableAttributesTest.java
+++ b/src/test/java/com/google/devtools/build/lib/analysis/ConfigurableAttributesTest.java
@@ -1266,6 +1266,45 @@ public void nonToolchainResolvingTargetsCantSelectDirectlyOnConstraints() throws
     assertContainsEvent("//conditions:apple is not a valid select() condition for //check:hello");
   }
 
+  @Test
+  public void selectDirectlyOnConstraintsWithAlias() throws Exception {
+    // Tests select()ing directly on a constraint_value (with no intermediate config_setting).
+    scratch.file(
+        "conditions/BUILD",
+        "constraint_setting(name = 'fruit')",
+        "constraint_value(name = 'apple', constraint_setting = 'fruit')",
+        "constraint_value(name = 'banana', constraint_setting = 'fruit')",
+        "platform(",
+        "    name = 'apple_platform',",
+        "    constraint_values = [':apple'],",
+        ")",
+        "platform(",
+        "    name = 'banana_platform',",
+        "    constraint_values = [':banana'],",
+        ")");
+    scratch.file(
+        "check/BUILD",
+        "filegroup(name = 'adep', srcs = ['afile'])",
+        "filegroup(name = 'bdep', srcs = ['bfile'])",
+        "alias(name = 'hello',",
+        "    actual = select({",
+        "        '//conditions:apple': ':adep',",
+        "        '//conditions:banana': ':bdep',",
+        "    }))");
+    checkRule(
+        "//check:hello",
+        "srcs",
+        ImmutableList.of("--platforms=//conditions:apple_platform"),
+        /*expected:*/ ImmutableList.of("src check/afile"),
+        /*not expected:*/ ImmutableList.of("src check/bfile"));
+    checkRule(
+        "//check:hello",
+        "srcs",
+        ImmutableList.of("--platforms=//conditions:banana_platform"),
+        /*expected:*/ ImmutableList.of("src check/bfile"),
+        /*not expected:*/ ImmutableList.of("src check/afile"));
+  }
+
   @Test
   public void multipleMatchErrorWhenAliasResolvesToSameSetting() throws Exception {
     scratch.file(