Add register_toolchains function to the WORKSPACE for registering toolchains to use.

Part of #2219.

Change-Id: Id6dfe6ec102f609bb19461242a098bf977be29ae
PiperOrigin-RevId: 161527986

1 files changed, 19 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/ExternalPackageUtil.java b/src/main/java/com/google/devtools/build/lib/rules/ExternalPackageUtil.java
index 4a73d05cdb..3a68b46903 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/ExternalPackageUtil.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/ExternalPackageUtil.java
@@ -26,6 +26,7 @@ import com.google.devtools.build.lib.packages.NoSuchPackageException;
 import com.google.devtools.build.lib.packages.Package;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.skyframe.PackageLookupValue;
+import com.google.devtools.build.lib.skyframe.PackageValue;
 import com.google.devtools.build.lib.skyframe.WorkspaceFileValue;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.util.Preconditions;
@@ -171,6 +172,24 @@ public class ExternalPackageUtil {
     return rule;
   }
 
+  /**
+   * Loads the external package and then returns the registered toolchain labels.
+   *
+   * @param env the environment to use for lookups
+   */
+  @Nullable
+  public static List<Label> getRegisteredToolchainLabels(Environment env)
+      throws ExternalPackageException, InterruptedException {
+    PackageValue externalPackageValue =
+        (PackageValue) env.getValue(PackageValue.key(Label.EXTERNAL_PACKAGE_IDENTIFIER));
+    if (externalPackageValue == null) {
+      return null;
+    }
+
+    Package externalPackage = externalPackageValue.getPackage();
+    return externalPackage.getRegisteredToolchainLabels();
+  }
+
   /** Exception thrown when something goes wrong accessing a rule. */
   public static class ExternalPackageException extends SkyFunctionException {
     public ExternalPackageException(NoSuchPackageException cause, Transience transience) {