Store reference iterations logs as separate tar member (Option A)

Author: PranjalManhgaye

tools/tests/README.md

@@ -94,9 +94,9 @@ In addition, in the directories of the cases executed, you can find `system-test
 When the tests fail at the results comparison step, this typically means that there are numerical regressions (unless something wrong went undetected in a previous step). We use [fieldcompare](https://gitlab.com/dglaeser/fieldcompare) to compare all [preCICE exports](https://precice.org/configuration-export.html) to reference results generated from a previous run. Relevant files:
 
 - `precice-exports/`: The coupling meshes of the test run.
-- `reference-results/`: The coupling meshes of the reference run, as stored on Git LFS, expanded into `reference-results-unpacked`. For implicit-coupling tests, the reference `.tar.gz` also contains an `iterations-logs/` directory with the reference `precice-*-iterations.log` files.
+- `reference-results/`: The coupling meshes of the reference run, as stored on Git LFS, expanded into `reference-results-unpacked`. For implicit-coupling tests, the reference `.tar.gz` also contains a separate `{case}.iterations-logs/` directory with the reference `precice-*-iterations.log` files.
 - `diff-results/`: Numerical difference of the results in the two directories (computed with `fieldcompare dir --diff precice-exports/ reference/`). These are only present on failed comparisons.
-- `iterations-logs/`: The `precice-*-iterations.log` files of the test run. Only present in implicit coupling tests and compared by SHA-256 hash against the copies unpacked from the reference `.tar.gz`.
+- `iterations-logs/`: The `precice-*-iterations.log` files of the test run. Only present in implicit coupling tests and compared by SHA-256 hash against the copies unpacked from `{case}.iterations-logs/` in the reference `.tar.gz`.
 
 To reproduce the comparison locally, use the [same fieldcompare command](https://github.com/precice/tutorials/blob/develop/tools/tests/docker-compose.field_compare.template.yaml):
 

tools/tests/generate_reference_results.py

@@ -2,7 +2,12 @@
 from metadata_parser.metdata import Tutorials, ReferenceResult
 from systemtests.TestSuite import TestSuites
 from systemtests.SystemtestArguments import SystemtestArguments
-from systemtests.Systemtest import Systemtest, GLOBAL_TIMEOUT, ITERATIONS_LOGS_DIR
+from systemtests.Systemtest import (
+    Systemtest,
+    GLOBAL_TIMEOUT,
+    ITERATIONS_LOGS_DIR,
+    reference_iterations_logs_tar_arcname,
+)
 from pathlib import Path
 from typing import List
 import shutil
@@ -24,19 +29,29 @@ def create_reference_tar_gz(
     output_filename: Path,
     iterations_logs: List[tuple[str, Path]],
 ) -> None:
-    """Archive precice-exports and optional iterations logs into one reference tar."""
+    """Archive precice-exports and optional iterations logs as separate top-level tar members."""
     stem = output_filename.name.replace(".tar.gz", "")
-    staging = system_test_dir / f".{stem}_reference_tar_staging"
-    if staging.exists():
-        shutil.rmtree(staging)
-    shutil.copytree(exports_dir, staging)
-    for rel, src in iterations_logs:
-        dest = staging / ITERATIONS_LOGS_DIR / rel
-        dest.parent.mkdir(parents=True, exist_ok=True)
-        shutil.copy2(src, dest)
-    with tarfile.open(output_filename, "w:gz") as tar:
-        tar.add(staging, arcname=stem)
-    shutil.rmtree(staging)
+    exports_staging = system_test_dir / f".{stem}_reference_exports_staging"
+    logs_staging = system_test_dir / f".{stem}_reference_logs_staging"
+    for staging in (exports_staging, logs_staging):
+        if staging.exists():
+            shutil.rmtree(staging)
+    shutil.copytree(exports_dir, exports_staging)
+    try:
+        with tarfile.open(output_filename, "w:gz") as tar:
+            tar.add(exports_staging, arcname=stem)
+            if iterations_logs:
+                for rel, src in iterations_logs:
+                    dest = logs_staging / rel
+                    dest.parent.mkdir(parents=True, exist_ok=True)
+                    shutil.copy2(src, dest)
+                tar.add(
+                    logs_staging,
+                    arcname=reference_iterations_logs_tar_arcname(stem),
+                )
+    finally:
+        shutil.rmtree(exports_staging, ignore_errors=True)
+        shutil.rmtree(logs_staging, ignore_errors=True)
 
 
 def get_machine_informations():

tools/tests/systemtests/Systemtest.py

@@ -27,6 +27,12 @@
 DIFF_RESULTS_DIR = "diff-results"
 ITERATIONS_LOGS_DIR = "iterations-logs"
 
+
+def reference_iterations_logs_tar_arcname(stem: str) -> str:
+    """Top-level tar member name for reference iterations logs (separate from VTU data)."""
+    return f"{stem}.{ITERATIONS_LOGS_DIR}"
+
+
 STAGE_LOG_FILES = {
     "build": "system-tests-build.log",
     "run": "system-tests-run.log",
@@ -727,8 +733,7 @@ def _unpacked_reference_iterations_logs_dir(self) -> Path:
         return (
             self.system_test_dir
             / PRECICE_REL_REFERENCE_DIR
-            / stem
-            / ITERATIONS_LOGS_DIR
+            / reference_iterations_logs_tar_arcname(stem)
         )
 
     def _collect_iterations_logs(