Allow Skylark rules to be private.
--
MOS_MIGRATED_REVID=97662036
diff --git a/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java b/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
index 05ad52a..0286796 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/RuleClass.java
@@ -225,7 +225,7 @@
* of that name already exists. Use {@link #overrideAttribute} in that case.
*/
public static final class Builder {
- private static final Pattern RULE_NAME_PATTERN = Pattern.compile("[A-Za-z][A-Za-z0-9_]*");
+ private static final Pattern RULE_NAME_PATTERN = Pattern.compile("[A-Za-z_][A-Za-z0-9_]*");
/**
* The type of the rule class, which determines valid names and required
