Allow fm step configuration values to be empty strings

src/ert/config/ert_config.py

@@ -134,6 +134,8 @@ def filter_env_dict(self, d):
                 new_value = self.substitute(value)
                 if new_value is None:
                     result[new_key] = None
+                elif not new_value:
+                    result[new_key] = ""
                 elif not (new_value[0] == "<" and new_value[-1] == ">"):
                     # Remove values containing "<XXX>". These are expected to be
                     # replaced by substitute, but were not.

tests/ert/unit_tests/config/test_ert_config.py

@@ -11,7 +11,7 @@
 from unittest.mock import MagicMock
 
 import pytest
-from hypothesis import assume, example, given, settings
+from hypothesis import HealthCheck, assume, example, given, settings
 from hypothesis import strategies as st
 from pydantic import RootModel, TypeAdapter
 
@@ -838,12 +838,16 @@ def test_that_include_statements_with_multiple_values_raises_error():
         )
 
 
+@pytest.mark.integration_test
+@settings(suppress_health_check=[HealthCheck.function_scoped_fixture])
 @pytest.mark.usefixtures("use_tmpdir")
-def test_fm_step_config_via_plugin_ends_up_json_data(monkeypatch):
+@given(anystring=st.text())
+def test_fm_step_config_via_plugin_ends_up_json_data(monkeypatch, anystring):
+    assume(not (anystring and anystring[0] == "<" and anystring[-1] == ">"))
     monkeypatch.setattr(
         ErtPluginManager,
         "get_forward_model_configuration",
-        MagicMock(return_value={"SOME_STEP": {"FOO": "bar"}}),
+        MagicMock(return_value={"SOME_STEP": {"FOO": anystring}}),
     )
     Path("SOME_STEP").write_text("EXECUTABLE /bin/ls", encoding="utf-8")
     Path("config.ert").write_text(
@@ -864,7 +868,7 @@ def test_fm_step_config_via_plugin_ends_up_json_data(monkeypatch):
         env_pr_fm_step=ert_config.env_pr_fm_step,
         run_id=None,
     )
-    assert step_json["jobList"][0]["environment"]["FOO"] == "bar"
+    assert step_json["jobList"][0]["environment"]["FOO"] == anystring
 
 
 @pytest.mark.usefixtures("use_tmpdir")

tests/ert/unit_tests/plugins/test_plugin_manager.py

@@ -83,6 +83,17 @@ def forward_model_configuration():
     )
 
 
+def test_fm_config_with_empty_string_for_step():
+    class SomePlugin:
+        @plugin(name="foo")
+        def forward_model_configuration():
+            return {"foo": {"com": ""}}
+
+    assert ErtPluginManager(plugins=[SomePlugin]).get_forward_model_configuration() == {
+        "foo": {"com": ""}
+    }
+
+
 def test_fm_config_merges_data_for_step():
     class SomePlugin:
         @plugin(name="foo")