Add first simple tests for "trivial" schema evolution

tests/CTestCustom.cmake

@@ -58,6 +58,9 @@ if ((NOT "@FORCE_RUN_ALL_TESTS@" STREQUAL "ON") AND (NOT "@USE_SANITIZER@" STREQ
     datamodel_def_store_roundtrip_root_extension
     datamodel_def_store_roundtrip_sio
     datamodel_def_store_roundtrip_sio_extension
+
+    write_old_data_root
+    read_new_data_root
   )
 
   foreach(version in @legacy_versions@)

tests/schema_evolution/CMakeLists.txt

@@ -12,3 +12,23 @@ PODIO_ADD_ROOT_IO_DICT(TestDataModel_v1Dict TestDataModel_v1 "${headers}" ${CMAK
 )
 
 PODIO_ADD_SIO_IO_BLOCKS(TestDataModel_v1 "${headers}" "${sources}")
+
+#--- Helper function to create a test in an environment that is suitable to
+#--- write data in an old schema version
+function(PODIO_CREATE_WRITE_OLD_DATA_TEST sourcefile additional_libs)
+  string( REPLACE ".cpp" "" name ${sourcefile} )
+  add_executable( ${name} ${sourcefile} )
+  add_test(NAME ${name} COMMAND ${name})
+
+  target_link_libraries(${name} PRIVATE TestDataModel_v1 ${additional_libs})
+  target_include_directories(${name} PRIVATE ${CMAKE_SOURCE_DIR}/tests/schema_evolution)
+
+  set_property(TEST ${name}
+    PROPERTY ENVIRONMENT
+    LD_LIBRARY_PATH=${CMAKE_BINARY_DIR}/src:${CMAKE_CURRENT_BINARY_DIR}:$<TARGET_FILE_DIR:ROOT::Tree>:$<$<TARGET_EXISTS:SIO::sio>:$<TARGET_FILE_DIR:SIO::sio>>:$ENV{LD_LIBRARY_PATH}
+    PODIO_SIO_BLOCK=${CMAKE_CURRENT_BINARY_DIR}
+    ROOT_INCLUDE_PATH=${CMAKE_CURRENT_BINARY_DIR}/datamodel_old:${CMAKE_SOURCE_DIR}/include
+  )
+endfunction()
+
+add_subdirectory(root_io)

tests/schema_evolution/README.md

@@ -0,0 +1,18 @@
+# Schema Evolution tests
+This folder contains tests for the schema evolution functionality in podio. The
+functionality is tested by first writing data with an old schema version and
+then reading in with the current schema version.
+[`datalayout_old.yaml`](./datalayout_old.yaml) holds the definition of the old
+version, using schema version 1, while the
+[`datalayout.yaml`](../datalayout.yaml) that is also used for the other I/O
+tests is used as the current version (schema version 2).
+
+## Differences between the two schema versions
+Since it is not immediately visible from the test code this list contains the
+differences between the two schema versions, and also how this evolution is
+tested (if it is supported)
+
+| component / datatype | difference from v1 to v2 | purpose of test | tested with |
+|--|--|--|--|
+| `SimpleStruct` | no `int y` member in v1 | Addition of new members in components | As  member of `ExampleWithArrayComponent` |
+| `ExampleHit` | no `double energy` member in v1 | Addition of new members in datatypes | Directly via `ExampleHit` |

tests/schema_evolution/datalayout_old.yaml

@@ -71,7 +71,6 @@ datatypes :
      - double x      // x-coordinate
      - double y      // y-coordinate
      - double z      // z-coordinate
-     - double energy // measured energy deposit
 
   ExampleMC :
     Description : "Example MC-particle"

tests/schema_evolution/read_new_data.h

@@ -0,0 +1,51 @@
+#ifndef PODIO_TESTS_SCHEMAEVOLUTION_READNEWDATA_H // NOLINT(llvm-header-guard): folder structure not suitable
+#define PODIO_TESTS_SCHEMAEVOLUTION_READNEWDATA_H // NOLINT(llvm-header-guard): folder structure not suitable
+
+#include "datamodel/ExampleHitCollection.h"
+#include "datamodel/ExampleWithArrayComponentCollection.h"
+
+#include "podio/Frame.h"
+
+#include <iostream>
+#include <string>
+
+int readSimpleStruct(const podio::Frame& event) {
+  const auto& coll = event.get<ExampleWithArrayComponentCollection>("simpleStructTest");
+  auto elem = coll[0];
+  const auto sstruct = elem.s();
+
+  if (sstruct.y != 0 || sstruct.x != 42 || sstruct.z != 123) {
+    return 1;
+  }
+  return 0;
+}
+
+int readExampleHit(const podio::Frame& event) {
+  const auto& coll = event.get<ExampleHitCollection>("datatypeMemberAdditionTest");
+  auto elem = coll[0];
+
+  if (elem.energy() != 0) {
+    return 1;
+  }
+  if (elem.x() != 1.23 || elem.y() != 1.23 || elem.z() != 1.23 || elem.cellID() != 0xcaffee) {
+    return 1;
+  }
+
+  return 0;
+}
+
+template <typename ReaderT>
+int read_new_data(const std::string& filename) {
+  ReaderT reader{};
+  reader.openFile(filename);
+
+  const auto event = podio::Frame(reader.readEntry("events", 0));
+
+  int result = 0;
+  result += readSimpleStruct(event);
+  result += readExampleHit(event);
+
+  return result;
+}
+
+#endif // PODIO_TESTS_SCHEMAEVOLUTION_WRITEOLDDATA_H

tests/schema_evolution/root_io/CMakeLists.txt

@@ -0,0 +1,4 @@
+PODIO_CREATE_WRITE_OLD_DATA_TEST(write_old_data_root.cpp "TestDataModel_v1Dict;podio::podioRootIO")
+
+CREATE_PODIO_TEST(read_new_data_root.cpp "TestDataModelDict;podioRootIO")
+set_property(TEST read_new_data_root PROPERTY DEPENDS write_old_data_root)

tests/schema_evolution/root_io/read_new_data_root.cpp

@@ -0,0 +1,7 @@
+#include "schema_evolution/read_new_data.h"
+
+#include "podio/ROOTFrameReader.h"
+
+int main() {
+  return read_new_data<podio::ROOTFrameReader>("example_data_old_schema.root");
+}

tests/schema_evolution/root_io/write_old_data_root.cpp

@@ -0,0 +1,7 @@
+#include "write_old_data.h"
+
+#include "podio/ROOTFrameWriter.h"
+
+int main() {
+  return writeData<podio::ROOTFrameWriter>("example_data_old_schema.root");
+}

tests/schema_evolution/write_old_data.h

@@ -0,0 +1,55 @@
+#ifndef PODIO_TESTS_SCHEMAEVOLUTION_WRITEOLDDATA_H // NOLINT(llvm-header-guard): folder structure not suitable
+#define PODIO_TESTS_SCHEMAEVOLUTION_WRITEOLDDATA_H // NOLINT(llvm-header-guard): folder structure not suitable
+
+#include "datamodel/ExampleHitCollection.h"
+#include "datamodel/ExampleWithArrayComponentCollection.h"
+
+#include "podio/Frame.h"
+
+#include <string>
+
+/// This is a datatype that holds a SimpleStruct component
+auto writeSimpleStruct() {
+  ExampleWithArrayComponentCollection coll;
+  auto elem = coll.create();
+  auto sstruct = SimpleStruct();
+  sstruct.x = 42;
+  sstruct.z = 123;
+  elem.s(sstruct);
+
+  return coll;
+}
+
+auto writeExampleHit() {
+  ExampleHitCollection coll;
+  auto elem = coll.create();
+  elem.x(1.23);
+  elem.y(1.23);
+  elem.z(1.23);
+  elem.cellID(0xcaffee);
+
+  return coll;
+}
+
+podio::Frame createFrame() {
+  podio::Frame event;
+
+  event.put(writeSimpleStruct(), "simpleStructTest");
+  event.put(writeExampleHit(), "dataTypeMemberAdditionTest");
+
+  return event;
+}
+
+template <typename WriterT>
+int writeData(const std::string& filename) {
+  WriterT writer(filename);
+
+  auto event = createFrame();
+  writer.writeFrame(event, "events");
+
+  writer.finish();
+
+  return 0;
+}
+
+#endif // PODIO_TESTS_SCHEMAEVOLUTION_WRITEOLDDATA_H