Fix default values in docs for attributes that are defined in ancestor classes.

For example, cc_binary and cc_test both inherit from the same rule class but
have different default values for the attribute stamp.

RELNOTES: None
PiperOrigin-RevId: 221399178

src/main/java/com/google/devtools/build/docgen/BuildDocCollector.java

diff --git a/src/main/java/com/google/devtools/build/docgen/BuildDocCollector.java b/src/main/java/com/google/devtools/build/docgen/BuildDocCollector.java
index df250d2..bd1fdf5 100644
--- a/src/main/java/com/google/devtools/build/docgen/BuildDocCollector.java
+++ b/src/main/java/com/google/devtools/build/docgen/BuildDocCollector.java
@@ -214,6 +214,17 @@
                 }
               }
               if (bestAttributeDoc != null) {
+                try {
+                  // We have to clone the matching RuleDocumentationAttribute here so that we don't
+                  // overwrite the reference to the actual attribute later by another attribute with
+                  // the same ancestor but different default values.
+                  bestAttributeDoc = (RuleDocumentationAttribute) bestAttributeDoc.clone();
+                } catch (CloneNotSupportedException e) {
+                  throw new BuildEncyclopediaDocException(
+                      bestAttributeDoc.getFileName(),
+                      bestAttributeDoc.getStartLineCnt(),
+                      "attribute doesn't support clone: " + e.toString());
+                }
                 // Add reference to the Attribute that the attribute doc is associated with
                 // in order to generate documentation for the Attribute.
                 bestAttributeDoc.setAttribute(attribute);

src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java

diff --git a/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java b/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java
index cac1303..2fde0f1 100644
--- a/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java
+++ b/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java
@@ -29,13 +29,14 @@
 import java.util.Set;
 
 /**
- * A class storing a rule attribute documentation along with some meta information.
- * The class provides functionality to compute the ancestry level of this attribute's
- * generator rule definition class compared to other rule definition classes.
+ * A class storing a rule attribute documentation along with some meta information. The class
+ * provides functionality to compute the ancestry level of this attribute's generator rule
+ * definition class compared to other rule definition classes.
  *
  * <p>Warning, two RuleDocumentationAttribute objects are equal based on only the attributeName.
  */
-public class RuleDocumentationAttribute implements Comparable<RuleDocumentationAttribute> {
+public class RuleDocumentationAttribute
+    implements Comparable<RuleDocumentationAttribute>, Cloneable {
 
   private static final ImmutableMap<Type<?>, String> TYPE_DESC =
       ImmutableMap.<Type<?>, String>builder()
@@ -70,6 +71,7 @@
   private Set<String> flags;
   private Attribute attribute;
 
+
   /**
    * Creates common RuleDocumentationAttribute such as deps or data.
    * These attribute docs have no definitionClass or htmlDocumentation (it's in the BE header).
@@ -102,6 +104,12 @@
     this.startLineCnt = startLineCnt;
     this.flags = flags;
     this.commonType = commonType;
+    this.fileName = fileName;
+  }
+
+  @Override
+  protected Object clone() throws CloneNotSupportedException {
+    return super.clone();
   }
 
   /**
@@ -118,6 +126,11 @@
     return attributeName;
   }
 
+  /** Returns the file name where the rule attribute is defined. */
+  public String getFileName() {
+    return fileName;
+  }
+
   /**
    * Returns whether this attribute is marked as deprecated.
    */