Allow strings as default values of labels

Strings now can be passed to the default parameter of attr.label,
attr.label_list, and attr.label_keyed_string_dict.

PiperOrigin-RevId: 160896987

2 files changed, 19 insertions, 7 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/packages/Attribute.java b/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
index ed8af8a6e7..ee2f8ac88f 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Attribute.java
@@ -54,6 +54,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -199,7 +200,7 @@ public final class Attribute implements Comparable<Attribute> {
      **/
     SPLIT(true);
 
-    private boolean defaultsToSelf;
+    private final boolean defaultsToSelf;
 
     ConfigurationTransition() {
       this(false);
@@ -657,21 +658,29 @@ public final class Attribute implements Comparable<Attribute> {
     /**
      * See value(TYPE) above. This method is only meant for Skylark usage.
      *
-     * <p>The parameter {@code context} is relevant iff the default value is a Label string.
-     * In this case, {@code context} must point to the parent Label in order to be able to convert
-     * the default value string to a proper Label.
+     * <p>The parameter {@code context} is relevant iff the default value is a Label string. In this
+     * case, {@code context} must point to the parent Label in order to be able to convert the
+     * default value string to a proper Label.
+     *
+     * @param parameterName The name of the attribute to use in error messages
      */
-    public Builder<TYPE> defaultValue(Object defaultValue, Object context)
+    public Builder<TYPE> defaultValue(
+        Object defaultValue, Object context, @Nullable String parameterName)
         throws ConversionException {
       Preconditions.checkState(!valueSet, "the default value is already set");
-      value = type.convert(defaultValue, "attribute " + name, context);
+      value =
+          type.convert(
+              defaultValue,
+              ((parameterName == null) ? "" : String.format("parameter '%s' of ", parameterName))
+                  + String.format("attribute '%s'", name),
+              context);
       valueSet = true;
       return this;
     }
 
     /** See value(TYPE) above. This method is only meant for Skylark usage. */
     public Builder<TYPE> defaultValue(Object defaultValue) throws ConversionException {
-      return defaultValue(defaultValue, null);
+      return defaultValue(defaultValue, null, null);
     }
 
     public boolean isValueSet() {
diff --git a/src/main/java/com/google/devtools/build/lib/packages/BuildType.java b/src/main/java/com/google/devtools/build/lib/packages/BuildType.java
index e0b1bbcf8c..418ac4d48f 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/BuildType.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/BuildType.java
@@ -250,6 +250,9 @@ public final class BuildType {
         return (Label) x;
       }
       try {
+        if (x instanceof String && context == null) {
+          return Label.parseAbsolute((String) x, false);
+        }
         return ((Label) context).getRelative(STRING.convert(x, what, context));
       } catch (LabelSyntaxException e) {
         throw new ConversionException("invalid label '" + x + "' in "