Allow switching on header processing (parse_headers or preprocess_headers)

for targets in the transitive closure of a target that is built.

Previously, this would only happen if a link action for the library containing
the headers was also built; this specifically means it did not trigger if
a library didn't contain source files, as there is no link action for such
libraries. That led to no header-only libraries would get their headers parsed,
which includes all cc_public_library rules.

Adding a flag to introduce this under so we can switch it on independently from
the blaze release. Once it is switched on, we can remove the edges in the
action graph from the link actions to the header processing actions.

--
MOS_MIGRATED_REVID=112782219

8 files changed, 112 insertions, 35 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcBinary.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcBinary.java
index 3afa030e1c..4e79ea0363 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcBinary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcBinary.java
@@ -300,8 +300,17 @@ public abstract class CcBinary implements RuleConfiguredTargetFactory {
 
     RuleConfiguredTargetBuilder ruleBuilder = new RuleConfiguredTargetBuilder(ruleContext);
     addTransitiveInfoProviders(
-        ruleContext, cppConfiguration, common, ruleBuilder, filesToBuild, ccCompilationOutputs,
-        cppCompilationContext, linkingOutputs, dwoArtifacts, transitiveLipoInfo, fake);
+        ruleContext,
+        cppConfiguration,
+        common,
+        ruleBuilder,
+        filesToBuild,
+        ccCompilationOutputs,
+        cppCompilationContext,
+        linkingOutputs,
+        dwoArtifacts,
+        transitiveLipoInfo,
+        fake);
 
     Map<Artifact, IncludeScannable> scannableMap = new LinkedHashMap<>();
     if (cppConfiguration.isLipoContextCollector()) {
@@ -586,23 +595,33 @@ public abstract class CcBinary implements RuleConfiguredTargetFactory {
     InstrumentedFilesProvider instrumentedFilesProvider = common.getInstrumentedFilesProvider(
         instrumentedObjectFiles, !TargetUtils.isTestRule(ruleContext.getRule()) && !fake);
 
+    NestedSet<Artifact> filesToCompile = ccCompilationOutputs.getFilesToCompile(
+        cppConfiguration.isLipoContextCollector(), CppHelper.usePic(ruleContext, false));
     builder
         .setFilesToBuild(filesToBuild)
         .add(CppCompilationContext.class, cppCompilationContext)
         .add(TransitiveLipoInfoProvider.class, transitiveLipoInfo)
-        .add(CcExecutionDynamicLibrariesProvider.class,
-            new CcExecutionDynamicLibrariesProvider(collectExecutionDynamicLibraryArtifacts(
-                ruleContext, linkingOutputs.getExecutionDynamicLibraries())))
-        .add(CcNativeLibraryProvider.class, new CcNativeLibraryProvider(
-            collectTransitiveCcNativeLibraries(ruleContext, linkingOutputs.getDynamicLibraries())))
+        .add(
+            CcExecutionDynamicLibrariesProvider.class,
+            new CcExecutionDynamicLibrariesProvider(
+                collectExecutionDynamicLibraryArtifacts(
+                    ruleContext, linkingOutputs.getExecutionDynamicLibraries())))
+        .add(
+            CcNativeLibraryProvider.class,
+            new CcNativeLibraryProvider(
+                collectTransitiveCcNativeLibraries(
+                    ruleContext, linkingOutputs.getDynamicLibraries())))
         .add(InstrumentedFilesProvider.class, instrumentedFilesProvider)
-        .add(CppDebugFileProvider.class, new CppDebugFileProvider(
-            dwoArtifacts.getDwoArtifacts(), dwoArtifacts.getPicDwoArtifacts()))
-        .addOutputGroup(OutputGroupProvider.TEMP_FILES,
-            getTemps(cppConfiguration, ccCompilationOutputs))
-        .addOutputGroup(OutputGroupProvider.FILES_TO_COMPILE,
-            common.getFilesToCompile(ccCompilationOutputs))
-        .addOutputGroup(OutputGroupProvider.COMPILATION_PREREQUISITES,
+        .add(
+            CppDebugFileProvider.class,
+            new CppDebugFileProvider(
+                dwoArtifacts.getDwoArtifacts(), dwoArtifacts.getPicDwoArtifacts()))
+        .addOutputGroup(
+            OutputGroupProvider.TEMP_FILES, getTemps(cppConfiguration, ccCompilationOutputs))
+        .addOutputGroup(
+            OutputGroupProvider.FILES_TO_COMPILE, filesToCompile)
+        .addOutputGroup(
+            OutputGroupProvider.COMPILATION_PREREQUISITES,
             CcCommon.collectCompilationPrerequisites(ruleContext, cppCompilationContext));
   }
 
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCommon.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCommon.java
index 2ede292346..49715198c4 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCommon.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCommon.java
@@ -27,7 +27,6 @@ import com.google.devtools.build.lib.analysis.TransitiveInfoCollection;
 import com.google.devtools.build.lib.cmdline.Label;
 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.BuildType;
 import com.google.devtools.build.lib.rules.apple.Platform;
 import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.FeatureConfiguration;
@@ -460,14 +459,6 @@ public final class CcCommon {
         CppFileTypes.LINKER_SCRIPT);
   }
 
-  NestedSet<Artifact> getFilesToCompile(CcCompilationOutputs compilationOutputs) {
-    if (cppConfiguration.isLipoContextCollector()) {
-      return NestedSetBuilder.emptySet(Order.STABLE_ORDER);
-    }
-    return NestedSetBuilder.wrap(Order.STABLE_ORDER,
-        compilationOutputs.getObjectFiles(CppHelper.usePic(ruleContext, false)));
-  }
-
   InstrumentedFilesProvider getInstrumentedFilesProvider(Iterable<Artifact> files,
       boolean withBaselineCoverage) {
     return cppConfiguration.isLipoContextCollector()
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCompilationOutputs.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCompilationOutputs.java
index 67162c20d7..aad62f05e7 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCompilationOutputs.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcCompilationOutputs.java
@@ -19,6 +19,7 @@ import com.google.common.collect.Iterables;
 import com.google.devtools.build.lib.actions.Artifact;
 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 java.util.ArrayList;
 import java.util.LinkedHashSet;
@@ -144,6 +145,20 @@ public class CcCompilationOutputs {
   public List<IncludeScannable> getLipoScannables() {
     return lipoScannables;
   }
+  
+  /**
+   * Returns the output files that are considered "copmiled" by this C++ compile action.
+   */
+  NestedSet<Artifact> getFilesToCompile(boolean isLipoContextCollector, boolean usePic) {
+    if (isLipoContextCollector) {
+      return NestedSetBuilder.<Artifact>emptySet(Order.STABLE_ORDER);
+    }
+    NestedSetBuilder<Artifact> files = NestedSetBuilder.stableOrder();
+    files.addAll(getObjectFiles(usePic));
+    files.addAll(getHeaderTokenFiles());
+    return files.build();
+  }
+
 
   public static final class Builder {
     private final Set<Artifact> objectFiles = new LinkedHashSet<>();
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibrary.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibrary.java
index 764b7f4441..411f9ac5e3 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibrary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibrary.java
@@ -231,7 +231,7 @@ public abstract class CcLibrary implements RuleConfiguredTargetFactory {
     CcLinkingOutputs linkedLibraries = info.getCcLinkingOutputsExcludingPrecompiledLibraries();
 
     NestedSet<Artifact> artifactsToForce =
-        collectHiddenTopLevelArtifacts(ruleContext, common, info.getCcCompilationOutputs());
+        collectHiddenTopLevelArtifacts(ruleContext, info.getCcCompilationOutputs());
 
     NestedSetBuilder<Artifact> filesBuilder = NestedSetBuilder.stableOrder();
     filesBuilder.addAll(LinkerInputs.toLibraryArtifacts(linkedLibraries.getStaticLibraries()));
@@ -268,11 +268,15 @@ public abstract class CcLibrary implements RuleConfiguredTargetFactory {
 
   }
 
-  private static NestedSet<Artifact> collectHiddenTopLevelArtifacts(RuleContext ruleContext,
-      CcCommon common, CcCompilationOutputs ccCompilationOutputs) {
+  private static NestedSet<Artifact> collectHiddenTopLevelArtifacts(
+      RuleContext ruleContext, CcCompilationOutputs ccCompilationOutputs) {
     // Ensure that we build all the dependencies, otherwise users may get confused.
     NestedSetBuilder<Artifact> artifactsToForceBuilder = NestedSetBuilder.stableOrder();
-    artifactsToForceBuilder.addTransitive(common.getFilesToCompile(ccCompilationOutputs));
+    boolean isLipoCollector =
+        ruleContext.getFragment(CppConfiguration.class).isLipoContextCollector();
+    boolean usePic = CppHelper.usePic(ruleContext, false);
+    artifactsToForceBuilder.addTransitive(
+        ccCompilationOutputs.getFilesToCompile(isLipoCollector, usePic));
     for (OutputGroupProvider dep :
         ruleContext.getPrerequisites("deps", Mode.TARGET, OutputGroupProvider.class)) {
       artifactsToForceBuilder.addTransitive(
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
index 6fd24c9659..f08baba335 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcLibraryHelper.java
@@ -744,7 +744,12 @@ public final class CcLibraryHelper {
     Map<String, NestedSet<Artifact>> outputGroups = new TreeMap<>();
     outputGroups.put(OutputGroupProvider.TEMP_FILES, getTemps(ccOutputs));
     if (emitCompileProviders) {
-      outputGroups.put(OutputGroupProvider.FILES_TO_COMPILE, getFilesToCompile(ccOutputs));
+      boolean isLipoCollector =
+          ruleContext.getFragment(CppConfiguration.class).isLipoContextCollector();
+      boolean usePic = CppHelper.usePic(ruleContext, false);
+      outputGroups.put(
+          OutputGroupProvider.FILES_TO_COMPILE,
+          ccOutputs.getFilesToCompile(isLipoCollector, usePic));
       outputGroups.put(OutputGroupProvider.COMPILATION_PREREQUISITES,
           CcCommon.collectCompilationPrerequisites(ruleContext, cppCompilationContext));
     }
@@ -1003,11 +1008,4 @@ public final class CcLibraryHelper {
         ? NestedSetBuilder.<Artifact>emptySet(Order.STABLE_ORDER)
         : compilationOutputs.getTemps();
   }
-
-  private NestedSet<Artifact> getFilesToCompile(CcCompilationOutputs compilationOutputs) {
-    return ruleContext.getFragment(CppConfiguration.class).isLipoContextCollector()
-        ? NestedSetBuilder.<Artifact>emptySet(Order.STABLE_ORDER)
-        : NestedSetBuilder.<Artifact>wrap(Order.STABLE_ORDER,
-            compilationOutputs.getObjectFiles(CppHelper.usePic(ruleContext, false)));
-  }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
index 31aa2f0fee..71045e4fd0 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfiguration.java
@@ -1526,6 +1526,13 @@ public class CppConfiguration extends BuildConfiguration.Fragment {
   public boolean skipStaticOutputs() {
     return cppOptions.skipStaticOutputs;
   }
+  
+  /**
+   * Returns whether we are processing headers in dependencies of built C++ targets.
+   */
+  public boolean processHeadersInDependencies() {
+    return cppOptions.processHeadersInDependencies;
+  }
 
   /**
    * Returns true if Fission is specified for this build and supported by the crosstool.
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
index a1015979e7..683e559a46 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppOptions.java
@@ -244,6 +244,16 @@ public class CppOptions extends FragmentOptions {
             + "network and disk I/O load (and thus, continuous build cycle times) by a lot.  "
             + "NOTE: use of this flag REQUIRES --distinct_host_configuration.")
   public boolean skipStaticOutputs;
+  
+  @Option(
+    name = "process_headers_in_dependencies",
+    defaultValue = "false",
+    category = "semantics",
+    help =
+        "When building a target //a:a, process headers in all targets that //a:a depends "
+            + "on (if header processing is enabled for the toolchain)."
+  )
+  public boolean processHeadersInDependencies;
 
   @Option(name = "copt",
           allowMultiple = true,
diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcLibraryConfiguredTargetTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcLibraryConfiguredTargetTest.java
index a11b7d7c3e..34c2786123 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcLibraryConfiguredTargetTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcLibraryConfiguredTargetTest.java
@@ -679,6 +679,39 @@ public class CcLibraryConfiguredTargetTest extends BuildViewTestCase {
   }
 
   @Test
+  public void testProcessHeadersInDependencies() throws Exception {
+    AnalysisMock.get()
+        .ccSupport()
+        .setupCrosstool(mockToolsConfig, MockCcSupport.HEADER_PROCESSING_FEATURE_CONFIGURATION);
+    useConfiguration("--features=parse_headers", "--process_headers_in_dependencies");
+    ConfiguredTarget x =
+        scratchConfiguredTarget(
+            "foo",
+            "x",
+            "cc_library(name = 'x', deps = [':y'])",
+            "cc_library(name = 'y', hdrs = ['y.h'])");
+    assertThat(ActionsTestUtil.baseNamesOf(getOutputGroup(x, OutputGroupProvider.HIDDEN_TOP_LEVEL)))
+        .isEqualTo("y.h.processed");
+  }
+  
+  @Test
+  public void testProcessHeadersInCompileOnlyMode() throws Exception {
+    AnalysisMock.get()
+        .ccSupport()
+        .setupCrosstool(mockToolsConfig, MockCcSupport.HEADER_PROCESSING_FEATURE_CONFIGURATION);
+    useConfiguration(
+        "--features=parse_headers", "--process_headers_in_dependencies");
+    ConfiguredTarget y =
+        scratchConfiguredTarget(
+            "foo",
+            "y",
+            "cc_library(name = 'x', deps = [':y'])",
+            "cc_library(name = 'y', hdrs = ['y.h'])");
+    assertThat(ActionsTestUtil.baseNamesOf(getOutputGroup(y, OutputGroupProvider.FILES_TO_COMPILE)))
+        .isEqualTo("y.h.processed");
+  }
+
+  @Test
   public void testIncludePathOrder() throws Exception {
     scratch.file("foo/BUILD",
         "cc_library(",