Fix string representation for the Root class

vladmos · aehlig · commit 065349116968 · 2017-07-19T10:20:55.000+02:00
It can be accessed as ctx.genfiles_dir and should be printed as before for
compatibility.

PiperOrigin-RevId: 162360940
diff --git a/src/main/java/com/google/devtools/build/lib/actions/Root.java b/src/main/java/com/google/devtools/build/lib/actions/Root.java
@@ -20,6 +20,8 @@
 import com.google.devtools.build.lib.skylarkinterface.SkylarkCallable;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkPrinter;
+import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -48,7 +50,7 @@
     doc = "A root for files. The roots are the directories containing files, and they are mapped "
         + "together into a single directory tree to form the execution environment.")
 @Immutable
-public final class Root implements Comparable<Root>, Serializable {
+public final class Root implements Comparable<Root>, Serializable, SkylarkValue {
 
   /**
    * Returns the given path as a source root. The path may not be {@code null}.
@@ -217,4 +219,9 @@ public boolean equals(Object o) {
   public String toString() {
     return path + (isSourceRoot() ? "[source]" : "[derived]");
   }
+
+  @Override
+  public void repr(SkylarkPrinter printer) {
+    printer.append(toString());
+  }
 }
