ENH: Don't persist metadata in ExportData

`generate_metadata` stored generated metadata internally. We don't need
to do this, and probably don't want to do this, because an ExportData
instance can be used to generate metadata across many objects.

src/fmu/dataio/dataio.py

@@ -7,7 +7,6 @@
 
 import os
 import warnings
-from copy import deepcopy
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, ClassVar, Dict, Final, List, Literal, Optional, Union
@@ -22,7 +21,6 @@
 from ._metadata import generate_export_metadata
 from ._utils import (
     detect_inside_rms,  # dataio_examples,
-    drop_nones,
     export_file,
     export_metadata_file,
     prettyprint_dict,
@@ -377,7 +375,6 @@ class ExportData:
     _usefmtflag: str = field(default="", init=False)
 
     # storing resulting state variables for instance, non-public:
-    _metadata: dict = field(default_factory=dict, init=False)
     _pwd: Path = field(default_factory=Path, init=False)
     _config_is_valid: bool = field(default=True, init=False)
     _fmurun: bool = field(default=False, init=False)
@@ -769,15 +766,11 @@ def generate_metadata(
 
         self._update_fmt_flag()
         fmudata = self._get_fmu_provider() if self._fmurun else None
-        self._metadata = drop_nones(
-            generate_export_metadata(
-                obj, self, fmudata, compute_md5=compute_md5
-            ).model_dump(mode="json", exclude_none=True, by_alias=True)
-        )
 
         logger.info("The metadata are now ready!")
-
-        return deepcopy(self._metadata)
+        return generate_export_metadata(
+            obj, self, fmudata, compute_md5=compute_md5
+        ).model_dump(mode="json", exclude_none=True, by_alias=True)
 
     def export(
         self,

tests/test_units/test_dataio.py

@@ -535,12 +535,13 @@ def test_exportdata_no_iter_folder(
     edata = ExportData(config=rmsglobalconfig, content="depth")
     assert edata._fmurun is True
 
-    edata.export(regsurf)
-
-    assert edata._metadata["fmu"]["realization"]["name"] == "realization-1"
-    assert edata._metadata["fmu"]["realization"]["id"] == 1
-    assert edata._metadata["fmu"]["iteration"]["name"] == "iter-0"
-    assert edata._metadata["fmu"]["iteration"]["id"] == 0
+    out = Path(edata.export(regsurf))
+    with open(out.parent / f".{out.name}.yml", encoding="utf-8") as f:
+        metadata = yaml.safe_load(f)
+    assert metadata["fmu"]["realization"]["name"] == "realization-1"
+    assert metadata["fmu"]["realization"]["id"] == 1
+    assert metadata["fmu"]["iteration"]["name"] == "iter-0"
+    assert metadata["fmu"]["iteration"]["id"] == 0
 
 
 def test_fmucontext_case_casepath(fmurun_prehook, rmsglobalconfig, regsurf):

tests/test_units/test_ert_context.py

@@ -8,10 +8,12 @@
 import logging
 import os
 import sys
+from pathlib import Path
 
 import fmu.dataio.dataio as dataio
 import pandas as pd
 import pytest
+import yaml
 from fmu.dataio._utils import prettyprint_dict
 
 logger = logging.getLogger(__name__)
@@ -115,8 +117,11 @@ def test_regsurf_export_file_fmurun(fmurun_w_casemetadata, rmsglobalconfig, regs
     )
     logger.info("Output is %s", output)
 
-    assert edata._metadata["access"]["ssdl"]["access_level"] == "restricted"
-    assert edata._metadata["data"]["unit"] == "forthnite"
+    out = Path(edata.export(regsurf))
+    with open(out.parent / f".{out.name}.yml", encoding="utf-8") as f:
+        metadata = yaml.safe_load(f)
+    assert metadata["access"]["ssdl"]["access_level"] == "restricted"
+    assert metadata["data"]["unit"] == "forthnite"
 
 
 # ======================================================================================

tests/test_units/test_objectdataprovider_class.py

@@ -1,9 +1,11 @@
 """Test the _ObjectData class from the _objectdata.py module"""
 
 import os
+from pathlib import Path
 
 import fmu.dataio as dataio
 import pytest
+import yaml
 from fmu.dataio._definitions import ConfigurationError, ValidFormats
 from fmu.dataio.providers.objectdata._provider import (
     objectdata_provider_factory,
@@ -141,4 +143,8 @@ def _run_case_fmu(fmurun_prehook, surfacepath):
     edata, mysurf = _export_data_from_rms(rmssetup, rmsglobalconfig, regsurf)
     set_ert_env_prehook(monkeypatch)
     case_meta = _run_case_fmu(fmurun_prehook, mysurf)
-    assert edata._metadata["data"] == case_meta["data"]
+
+    out = Path(mysurf)
+    with open(out.parent / f".{out.name}.yml", encoding="utf-8") as f:
+        metadata = yaml.safe_load(f)
+    assert metadata["data"] == case_meta["data"]

tests/test_units/test_rms_context.py

@@ -13,6 +13,7 @@
 import fmu.dataio.readers as readers
 import pandas as pd
 import pytest
+import yaml
 from fmu.dataio._definitions import FmuContext
 from fmu.dataio._utils import prettyprint_dict
 from fmu.dataio.dataio import ValidationError
@@ -224,8 +225,11 @@ def test_regsurf_export_file_fmurun(
     )
     logger.info("Output is %s", output)
 
-    assert edata._metadata["access"]["ssdl"]["access_level"] == "restricted"
-    assert edata._metadata["data"]["unit"] == "forthnite"
+    out = Path(edata.export(regsurf))
+    with open(out.parent / f".{out.name}.yml", encoding="utf-8") as f:
+        metadata = yaml.safe_load(f)
+    assert metadata["access"]["ssdl"]["access_level"] == "restricted"
+    assert metadata["data"]["unit"] == "forthnite"
 
 
 # ======================================================================================