[Fix] (CI, android-plugin): keep a failed Android retrace's result artifact, and echo the logs a failed replay already wrote

.github/workflows/apk.yml

@@ -531,22 +531,41 @@ jobs:
           )
 
           if ((${#failed_cases[@]})); then
-            echo "Retaining fixtures for failed retrace case(s):"
+            echo "Retaining fixtures and results for failed retrace case(s):"
             printf '  %s\n' "${!failed_cases[@]}"
           else
-            echo "All retrace jobs succeeded; no fixtures need to be retained."
+            echo "All retrace jobs succeeded; nothing needs to be retained."
           fi
 
           deleted=0
           retained=0
           while IFS=$'\t' read -r artifact_id artifact_name; do
+            keep=0
             if [[ "${artifact_name}" == MobileGL-trace-fixture-* ]]; then
               case_name="${artifact_name#MobileGL-trace-fixture-}"
               if [[ -v "failed_cases[${case_name}]" ]]; then
-                echo "Retaining ${artifact_name} (${artifact_id}) for failed retrace."
-                ((retained += 1))
-                continue
+                keep=1
               fi
+            elif [[ "${artifact_name}" == MobileGL-android-retrace-result-* ]]; then
+              # The result artifact carries mobilegl.log, retrace.log, logcat,
+              # the emulator log and the actual/diff images - the only record of
+              # why a retrace failed. Its name ends in -<backend>-<case>, so a
+              # suffix match on the case name keeps both backends' results for a
+              # case that failed on either of them, which is what a comparison
+              # needs. The match is anchored at the end, so a case name that is a
+              # prefix of a longer one does not retain the longer one's results.
+              for case_name in "${!failed_cases[@]}"; do
+                if [[ "${artifact_name}" == *-"${case_name}" ]]; then
+                  keep=1
+                  break
+                fi
+              done
+            fi
+
+            if ((keep)); then
+              echo "Retaining ${artifact_name} (${artifact_id}) for failed retrace."
+              ((retained += 1))
+              continue
             fi
 
             echo "Deleting ${artifact_name} (${artifact_id})"

android-plugin/trace-replay-ci.sh

@@ -344,6 +344,22 @@ run_retrace() {
   copy_app_artifact "${app_dir}/output/retrace.log" "${result_dir}/retrace.log"
   copy_app_artifact "${app_dir}/output/mobilegl.log" "${result_dir}/mobilegl.log"
 
+  # A replay that wrote result.json but did not pass used to print nothing but
+  # the JSON, which for a non-zero statusCode says only "retrace failed with
+  # status N". The logs that say why are already on disk here, so echo their
+  # tails the same way the missing-result.json path does; the job log is the one
+  # place a failure stays readable after the result artifact expires.
+  if ! grep -q '"passed"[[:space:]]*:[[:space:]]*true' "${result_dir}/result.json"; then
+    if [ -s "${result_dir}/retrace.log" ]; then
+      echo "trace-replay-ci.sh: tail of retrace.log:" >&2
+      tail -200 "${result_dir}/retrace.log" >&2
+    fi
+    if [ -s "${result_dir}/mobilegl.log" ]; then
+      echo "trace-replay-ci.sh: tail of mobilegl.log:" >&2
+      tail -200 "${result_dir}/mobilegl.log" >&2
+    fi
+  fi
+
   "${PYTHON}" -c 'import json, sys; result = json.load(open(sys.argv[1], encoding="utf-8")); sys.exit(0 if result.get("passed") else f"trace replay failed: {result}")' "${result_dir}/result.json"
 }