Expose Skylark API to the C++ toolchain

This is an implementation of the design at
https://docs.google.com/document/d/1g91BWJITcYw_X-VxsDC0VgUn5E9g0kRBGoBSpoO41gA/edit>.
More thorough documentation will be sent in a separate cl. The api was approved
at
https://docs.google.com/document/d/1M8JA7kzZnWpLZ3WEX9rp6k2u_nlwE8smsHYgVTSSJ9k/edit?ts=5b292400#.

Work towards #4571 (only the docs are missing).

RELNOTES: None.
PiperOrigin-RevId: 202464331

src/main/java/com/google/devtools/build/lib/rules/cpp/CcModule.java

@@ -14,15 +14,180 @@
 
 package com.google.devtools.build.lib.rules.cpp;
 
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.analysis.platform.ToolchainInfo;
+import com.google.devtools.build.lib.collect.nestedset.NestedSet;
+import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
+import com.google.devtools.build.lib.collect.nestedset.Order;
 import com.google.devtools.build.lib.packages.Provider;
+import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.FeatureConfiguration;
 import com.google.devtools.build.lib.skylarkbuildapi.cpp.CcModuleApi;
+import com.google.devtools.build.lib.syntax.EvalException;
+import com.google.devtools.build.lib.syntax.EvalUtils;
+import com.google.devtools.build.lib.syntax.SkylarkDict;
+import com.google.devtools.build.lib.syntax.SkylarkList;
+import com.google.devtools.build.lib.syntax.SkylarkNestedSet;
+import javax.annotation.Nullable;
 
 /** A module that contains Skylark utilities for C++ support. */
-public class CcModule implements CcModuleApi {
+public class CcModule
+    implements CcModuleApi<CcToolchainProvider, FeatureConfiguration, CcToolchainVariables> {
 
   @Override
   public Provider getCcToolchainProvider() {
     return ToolchainInfo.PROVIDER;
   }
+
+  @Override
+  public FeatureConfiguration configureFeatures(
+      CcToolchainProvider toolchain,
+      SkylarkList<String> requestedFeatures,
+      SkylarkList<String> unsupportedFeatures)
+      throws EvalException {
+    return CcCommon.configureFeaturesOrThrowEvalException(
+        ImmutableSet.copyOf(requestedFeatures),
+        ImmutableSet.copyOf(unsupportedFeatures),
+        toolchain);
+  }
+
+  @Override
+  public String getToolForAction(FeatureConfiguration featureConfiguration, String actionName) {
+    return featureConfiguration
+        .getToolForAction(actionName)
+        .getToolPathFragment()
+        .getSafePathString();
+  }
+
+  @Override
+  public boolean isEnabled(FeatureConfiguration featureConfiguration, String featureName) {
+    return featureConfiguration.isEnabled(featureName);
+  }
+
+  @Override
+  public SkylarkList<String> getCommandLine(
+      FeatureConfiguration featureConfiguration,
+      String actionName,
+      CcToolchainVariables variables) {
+    return SkylarkList.createImmutable(featureConfiguration.getCommandLine(actionName, variables));
+  }
+
+  @Override
+  public SkylarkDict<String, String> getEnvironmentVariable(
+      FeatureConfiguration featureConfiguration,
+      String actionName,
+      CcToolchainVariables variables) {
+    return SkylarkDict.copyOf(
+        null, featureConfiguration.getEnvironmentVariables(actionName, variables));
+  }
+
+  @Override
+  public CcToolchainVariables getCompileBuildVariables(
+      CcToolchainProvider ccToolchainProvider,
+      FeatureConfiguration featureConfiguration,
+      Object sourceFile,
+      Object outputFile,
+      Object userCompileFlags,
+      Object includeDirs,
+      Object quoteIncludeDirs,
+      Object systemIncludeDirs,
+      Object defines,
+      boolean usePic,
+      boolean addLegacyCxxOptions)
+      throws EvalException {
+    return CompileBuildVariables.setupVariablesOrThrowEvalException(
+        featureConfiguration,
+        ccToolchainProvider,
+        convertFromNoneable(sourceFile, /* defaultValue= */ null),
+        convertFromNoneable(outputFile, /* defaultValue= */ null),
+        /* gcnoFile= */ null,
+        /* dwoFile= */ null,
+        /* ltoIndexingFile= */ null,
+        /* includes= */ ImmutableList.of(),
+        asStringNestedSet(userCompileFlags),
+        /* cppModuleMap= */ null,
+        usePic,
+        /* fakeOutputFile= */ null,
+        /* fdoStamp= */ null,
+        /* dotdFileExecPath= */ null,
+        /* variablesExtensions= */ ImmutableList.of(),
+        /* additionalBuildVariables= */ ImmutableMap.of(),
+        /* directModuleMaps= */ ImmutableList.of(),
+        asStringNestedSet(includeDirs),
+        asStringNestedSet(quoteIncludeDirs),
+        asStringNestedSet(systemIncludeDirs),
+        asStringNestedSet(defines),
+        addLegacyCxxOptions);
+  }
+
+  @Override
+  public CcToolchainVariables getLinkBuildVariables(
+      CcToolchainProvider ccToolchainProvider,
+      FeatureConfiguration featureConfiguration,
+      Object librarySearchDirectories,
+      Object runtimeLibrarySearchDirectories,
+      Object userLinkFlags,
+      Object outputFile,
+      Object paramFile,
+      Object defFile,
+      boolean isUsingLinkerNotArchiver,
+      boolean isCreatingSharedLibrary,
+      boolean mustKeepDebug,
+      boolean useTestOnlyFlags,
+      boolean isStaticLinkingMode)
+      throws EvalException {
+    return LinkBuildVariables.setupVariables(
+        isUsingLinkerNotArchiver,
+        /* binDirectoryPath= */ null,
+        convertFromNoneable(outputFile, /* defaultValue= */ null),
+        isCreatingSharedLibrary,
+        convertFromNoneable(paramFile, /* defaultValue= */ null),
+        /* thinltoParamFile= */ null,
+        /* thinltoMergedObjectFile= */ null,
+        mustKeepDebug,
+        /* symbolCounts= */ null,
+        ccToolchainProvider,
+        featureConfiguration,
+        useTestOnlyFlags,
+        /* isLtoIndexing= */ false,
+        asStringNestedSet(userLinkFlags),
+        /* interfaceLibraryBuilder= */ null,
+        /* interfaceLibraryOutput= */ null,
+        /* ltoOutputRootPrefix= */ null,
+        convertFromNoneable(defFile, /* defaultValue= */ null),
+        /* fdoSupport= */ null,
+        asStringNestedSet(runtimeLibrarySearchDirectories),
+        /* librariesToLink= */ null,
+        asStringNestedSet(librarySearchDirectories),
+        /* isLegacyFullyStaticLinkingMode= */ false,
+        isStaticLinkingMode);
+  }
+
+  @Override
+  public CcToolchainVariables getVariables() {
+    return CcToolchainVariables.EMPTY;
+  }
+
+  /**
+   * Converts an object that can be the NoneType to the actual object if it is not or returns the
+   * default value if none.
+   */
+  @SuppressWarnings("unchecked")
+  protected static <T> T convertFromNoneable(Object obj, @Nullable T defaultValue) {
+    if (EvalUtils.isNullOrNone(obj)) {
+      return defaultValue;
+    }
+    return (T) obj;
+  }
+
+  /** Converts an object that can be the either SkylarkNestedSet or None into NestedSet. */
+  protected NestedSet<String> asStringNestedSet(Object o) throws EvalException {
+    SkylarkNestedSet skylarkNestedSet = convertFromNoneable(o, /* defaultValue= */ null);
+    if (skylarkNestedSet != null) {
+      return skylarkNestedSet.getSet(String.class);
+    } else {
+      return NestedSetBuilder.emptySet(Order.STABLE_ORDER);
+    }
+  }
 }