Open source IncludeScanning glue code

One tiny step after the other.

PiperOrigin-RevId: 205378056

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

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/IncludeScanning.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/IncludeScanning.java
new file mode 100644
index 0000000..ba0e13a
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/IncludeScanning.java
@@ -0,0 +1,50 @@
+// Copyright 2018 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.rules.cpp;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.actions.ActionExecutionContext;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.ExecException;
+import com.google.devtools.build.lib.rules.cpp.IncludeScanner.IncludeScannerSupplier;
+import com.google.devtools.build.lib.rules.cpp.IncludeScanner.IncludeScanningPreparer;
+import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
+import javax.annotation.Nullable;
+
+/** Runs include scanning on actions, if include scanning is enabled. */
+public class IncludeScanning implements IncludeProcessing {
+  @AutoCodec public static final IncludeScanning INSTANCE = new IncludeScanning();
+
+  @Override
+  public @Nullable Iterable<Artifact> determineAdditionalInputs(
+      @Nullable IncludeScannerSupplier includeScannerSupplier,
+      CppCompileAction action,
+      ActionExecutionContext actionExecutionContext)
+      throws ExecException, InterruptedException {
+    // Return null when no include scanning occurs, as opposed to an empty set, to distinguish from
+    // the case where includes are scanned but none are found.
+    if (!action.shouldScanIncludes()) {
+      return null;
+    }
+
+    return IncludeScanningPreparer.scanForIncludedInputs(
+        action,
+        Preconditions.checkNotNull(includeScannerSupplier, action),
+        action.getIncludeScanningHeaderData(),
+        action,
+        actionExecutionContext,
+        actionExecutionContext.getInputPath(action.getSourceFile()).getPathString());
+  }
+}