Update toolchain resolution to use ToolchainTypeRequirement.

Actually updating the logic to check mandatory/optional is still TODO.

Part of bazelbuild#14726.

src/main/java/com/google/devtools/build/lib/skyframe/BUILD

@@ -248,6 +248,7 @@ java_library(
         "//src/main/java/com/google/devtools/build/lib/analysis:config/fragment_options",
         "//src/main/java/com/google/devtools/build/lib/analysis:config/host_transition",
         "//src/main/java/com/google/devtools/build/lib/analysis:config/invalid_configuration_exception",
+        "//src/main/java/com/google/devtools/build/lib/analysis:config/toolchain_type_requirement",
         "//src/main/java/com/google/devtools/build/lib/analysis:config/transitions/configuration_transition",
         "//src/main/java/com/google/devtools/build/lib/analysis:config/transitions/no_transition",
         "//src/main/java/com/google/devtools/build/lib/analysis:config/transitions/null_transition",
@@ -2529,6 +2530,7 @@ java_library(
     deps = [
         ":build_configuration",
         ":sky_functions",
+        "//src/main/java/com/google/devtools/build/lib/analysis:config/toolchain_type_requirement",
         "//src/main/java/com/google/devtools/build/lib/cmdline",
         "//src/main/java/com/google/devtools/build/skyframe:skyframe-objects",
         "//third_party:auto_value",

src/main/java/com/google/devtools/build/lib/skyframe/RegisteredToolchainsCycleReporter.java

@@ -20,8 +20,8 @@
 import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.analysis.config.ToolchainTypeRequirement;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.events.ExtendedEventHandler;
@@ -89,11 +89,13 @@ public boolean maybeReportCycle(
             return String.format("toolchain type %s", toolchainType);
           }
           if (input.argument() instanceof ToolchainContextKey) {
-            ImmutableSet<Label> toolchainTypes =
-                ((ToolchainContextKey) input.argument()).requiredToolchainTypeLabels();
-            return String.format(
-                "toolchain types %s",
-                toolchainTypes.stream().map(Label::toString).collect(joining(", ")));
+            ToolchainContextKey toolchainContextKey = (ToolchainContextKey) input.argument();
+            String toolchainTypes =
+                toolchainContextKey.toolchainTypes().stream()
+                    .map(ToolchainTypeRequirement::toolchainType)
+                    .map(Label::toString)
+                    .collect(joining(", "));
+            return String.format("toolchain types %s", toolchainTypes);
           }
 
           throw new UnsupportedOperationException();

src/main/java/com/google/devtools/build/lib/skyframe/ToolchainContextKey.java

@@ -13,9 +13,12 @@
 // limitations under the License.
 package com.google.devtools.build.lib.skyframe;
 
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
+
 import com.google.auto.value.AutoValue;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableSet;
+import com.google.devtools.build.lib.analysis.config.ToolchainTypeRequirement;
 import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.skyframe.SkyFunctionName;
 import com.google.devtools.build.skyframe.SkyKey;
@@ -31,7 +34,7 @@ public abstract class ToolchainContextKey implements SkyKey {
   /** Returns a new {@link Builder}. */
   public static Builder key() {
     return new AutoValue_ToolchainContextKey.Builder()
-        .requiredToolchainTypeLabels(ImmutableSet.of())
+        .toolchainTypes(ImmutableSet.of())
         .execConstraintLabels(ImmutableSet.of())
         .forceExecutionPlatform(Optional.empty())
         .debugTarget(false);
@@ -44,7 +47,7 @@ public SkyFunctionName functionName() {
 
   abstract BuildConfigurationKey configurationKey();
 
-  abstract ImmutableSet<Label> requiredToolchainTypeLabels();
+  abstract ImmutableSet<ToolchainTypeRequirement> toolchainTypes();
 
   abstract ImmutableSet<Label> execConstraintLabels();
 
@@ -57,9 +60,21 @@ public SkyFunctionName functionName() {
   public interface Builder {
     Builder configurationKey(BuildConfigurationKey key);
 
-    Builder requiredToolchainTypeLabels(ImmutableSet<Label> requiredToolchainTypeLabels);
+    // TODO(katre): Remove this once all callers use toolchainTypes.
+    default Builder requiredToolchainTypeLabels(Label... requiredToolchainTypeLabels) {
+      return this.requiredToolchainTypeLabels(ImmutableSet.copyOf(requiredToolchainTypeLabels));
+    }
+
+    // TODO(katre): Remove this once all callers use toolchainTypes.
+    default Builder requiredToolchainTypeLabels(ImmutableSet<Label> requiredToolchainTypeLabels) {
+      ImmutableSet<ToolchainTypeRequirement> toolchainTypeRequirements =
+          requiredToolchainTypeLabels.stream()
+              .map(label -> ToolchainTypeRequirement.builder().toolchainType(label).build())
+              .collect(toImmutableSet());
+      return this.toolchainTypes(toolchainTypeRequirements);
+    }
 
-    Builder requiredToolchainTypeLabels(Label... requiredToolchainTypeLabels);
+    Builder toolchainTypes(ImmutableSet<ToolchainTypeRequirement> toolchainTypes);
 
     Builder execConstraintLabels(ImmutableSet<Label> execConstraintLabels);
 

src/main/java/com/google/devtools/build/lib/skyframe/ToolchainResolutionFunction.java

@@ -28,6 +28,7 @@
 import com.google.common.collect.Table;
 import com.google.devtools.build.lib.analysis.PlatformConfiguration;
 import com.google.devtools.build.lib.analysis.config.BuildConfigurationValue;
+import com.google.devtools.build.lib.analysis.config.ToolchainTypeRequirement;
 import com.google.devtools.build.lib.analysis.platform.ConstraintValueInfo;
 import com.google.devtools.build.lib.analysis.platform.PlatformInfo;
 import com.google.devtools.build.lib.analysis.platform.ToolchainTypeInfo;
@@ -83,13 +84,17 @@ public UnloadedToolchainContext compute(SkyKey skyKey, Environment env)
           key.debugTarget()
               || configuration
                   .getFragment(PlatformConfiguration.class)
-                  .debugToolchainResolution(key.requiredToolchainTypeLabels());
+                  .debugToolchainResolution(
+                      key.toolchainTypes().stream()
+                          .map(ToolchainTypeRequirement::toolchainType)
+                          .collect(toImmutableSet()));
 
       // Load the configured target for the toolchain types to ensure that they are valid and
       // resolve aliases.
       ImmutableMap<Label, ToolchainTypeInfo> resolvedToolchainTypes =
-          loadToolchainTypes(env, configuration, key.requiredToolchainTypeLabels());
+          loadToolchainTypes(env, configuration, key.toolchainTypes());
       builder.setRequestedLabelToToolchainType(resolvedToolchainTypes);
+      // TODO(katre): Need to correct for possible aliases, map to mandatory/optional.
       ImmutableSet<Label> resolvedToolchainTypeLabels =
           resolvedToolchainTypes.values().stream()
               .map(ToolchainTypeInfo::typeLabel)
@@ -149,10 +154,11 @@ public UnloadedToolchainContext compute(SkyKey skyKey, Environment env)
   private static ImmutableMap<Label, ToolchainTypeInfo> loadToolchainTypes(
       Environment environment,
       BuildConfigurationValue configuration,
-      ImmutableSet<Label> requestedToolchainTypeLabels)
+      ImmutableSet<ToolchainTypeRequirement> toolchainTypeRequirements)
       throws InvalidToolchainTypeException, InterruptedException, ValueMissingException {
     ImmutableSet<ConfiguredTargetKey> toolchainTypeKeys =
-        requestedToolchainTypeLabels.stream()
+        toolchainTypeRequirements.stream()
+            .map(ToolchainTypeRequirement::toolchainType)
             .map(
                 label ->
                     ConfiguredTargetKey.builder()
@@ -361,7 +367,7 @@ private static void determineToolchainImplementations(
           NoMatchingPlatformException, UnresolvedToolchainsException,
           InvalidToolchainLabelException {
 
-    // Find the toolchains for the required toolchain types.
+    // Find the toolchains for the requested toolchain types.
     List<SingleToolchainResolutionKey> registeredToolchainKeys = new ArrayList<>();
     for (Label toolchainTypeLabel : requiredToolchainTypeLabels) {
       registeredToolchainKeys.add(
@@ -420,6 +426,7 @@ private static void determineToolchainImplementations(
     ImmutableSet<ToolchainTypeInfo> requiredToolchainTypes = requiredToolchainTypesBuilder.build();
 
     // Find and return the first execution platform which has all required toolchains.
+    // TODO(katre): Handle mandatory/optional.
     Optional<ConfiguredTargetKey> selectedExecutionPlatformKey =
         findExecutionPlatformForToolchains(
             requiredToolchainTypes,