Skip over runfiles middleman artifacts without a RunfilesSupplier (#2…

…4086)

Fixes #24061

src/main/java/com/google/devtools/build/lib/exec/CompactSpawnLogContext.java

@@ -399,6 +399,16 @@ private int logInputSet(
           for (ActionInput input : set.getLeaves()) {
             if (input instanceof Artifact artifact && artifact.isMiddlemanArtifact()) {
               RunfilesTree runfilesTree = runfilesTrees.get(artifact);
+              if (runfilesTree == null) {
+                // This happens for spawns that don't keep their RunfilesSuppliers in sync with
+                // the middleman artifacts in their inputs.
+                // The known examples are test spawns that include the lcov merger as a middleman
+                // artifact, but don't merge in its supplier, as well as split coverage
+                // postprocessing spawns, which include the test runfiles middleman but not its
+                // supplier. Since the supplier is what causes the runfiles tree to be materialized,
+                // we can safely ignore these stray middleman artifacts.
+                continue;
+              }
               builder.addInputIds(
                   logRunfilesTree(
                       runfilesTree, inputMetadataProvider, fileSystem, isTestRunnerSpawn));

src/test/shell/bazel/bazel_execlog_test.sh

@@ -203,6 +203,27 @@ EOF
   [[ -e ../output.compact ]] || fail "no compact log produced"
 }
 
+function test_coverage() {
+  cat > BUILD <<'EOF'
+sh_test(
+    name = "test",
+    srcs = ["test.sh"],
+)
+EOF
+  cat > test.sh <<'EOF'
+echo "hello world"
+EOF
+  chmod +x test.sh
+
+  bazel coverage //:test --execution_log_compact_file=output.compact >> $TEST_log 2>&1 || fail "coverage failed"
+  [[ -e output.compact ]] || fail "no compact log produced"
+
+  rm output.compact
+  bazel coverage //:test --experimental_split_coverage_postprocessing --experimental_fetch_all_coverage_outputs \
+    --execution_log_compact_file=output.compact >> $TEST_log 2>&1 || fail "coverage failed"
+  [[ -e output.compact ]] || fail "no compact log produced"
+}
+
 function test_no_remote_cache() {
   cat > BUILD <<'EOF'
 genrule(