Embed the == and .equal number of linkstamp artifacts in the nativede…

…ps hashed filename, since normally there should be only one linkstamp artifact in any case.

This shouldn't affect filenames or performance except in the exceptional mysterious case we're trying to track down.

PiperOrigin-RevId: 228882225

src/main/java/com/google/devtools/build/lib/rules/nativedeps/NativeDepsHelper.java

@@ -19,6 +19,8 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Sets;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.analysis.RuleContext;
@@ -52,6 +54,7 @@
 import java.util.Collection;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Helper class to create a dynamic library for rules which support integration with native code.
@@ -367,6 +370,19 @@ private static PathFragment getSharedNativeDepsPath(Iterable<Artifact> linkerInp
       fp.addString(input.getExecPathString());
       linkstampsSize++;
     }
+    // TODO(b/120206809): remove debugging info here (and in this whole filename construction).
+    String linkstampsString = Integer.toString(linkstampsSize);
+    if (linkstampsSize > 1) {
+      Set<Artifact> identitySet = Sets.newIdentityHashSet();
+      Iterables.addAll(identitySet, linkstamps);
+      if (identitySet.size() < linkstampsSize) {
+        linkstampsString += "_" + identitySet.size();
+      }
+      ImmutableSet<Artifact> uniqueLinkStamps = ImmutableSet.copyOf(linkstamps);
+      if (uniqueLinkStamps.size() < linkstampsSize) {
+        linkstampsString += "__" + uniqueLinkStamps.size();
+      }
+    }
     int buildInfoSize = 0;
     for (Artifact input : buildInfoArtifacts) {
       fp.addString(input.getExecPathString());
@@ -381,7 +397,7 @@ private static PathFragment getSharedNativeDepsPath(Iterable<Artifact> linkerInp
             + "_"
             + linkopts.size()
             + "_"
-            + linkstampsSize
+            + linkstampsString
             + "_"
             + buildInfoSize
             + "_"