Allow users without equilibrium to run ert with FLOW simulator.

Create flow_config.yml config file if it is not found in the env variables.

src/ert/plugins/hook_implementations/forward_model_steps.py

@@ -312,19 +312,20 @@ def documentation() -> Optional[ForwardModelStepDocumentation]:
         return ForwardModelStepDocumentation(
             category="simulators.reservoir",
             examples="""
-The version, number of cpu and whether or not to ignore errors can
-be configured in the configuration file when adding the job, as such:
-
 .. code-block:: bash
 
-    FORWARD_MODEL FLOW(<ECLBASE>, <VERSION>=xxxx, <OPTS>="--ignore-errors")
+    FORWARD_MODEL FLOW(<ECLBASE>, <OPTS>="--ignore-errors")
 
 The :code:`OPTS` argument is optional and can be removed, thus running flow
 without ignoring errors.
+
+ERT will be able to run with flow only if OPM FLOW simulator is installed and available
+in the user $PATH environment varaible.
+
+Currently ERT does not support changing the default options for the flow simulator.
+
 """,
-            description="""
-Forward model for OPM Flow
-""",
+            description="""Forward model for OPM Flow simulator""",
         )
 
 

src/ert/resources/forward-models/res/script/ecl_config.py

@@ -1,7 +1,9 @@
 import os
 import re
+import shutil
 import subprocess
 import sys
+from pathlib import Path
 from typing import Any, Dict, List, Optional
 
 import yaml
@@ -203,8 +205,33 @@ class FlowConfig(EclConfig):
 
     def __init__(self):
         config_file = os.getenv("FLOW_SITE_CONFIG", default=self.DEFAULT_CONFIG_FILE)
+        if not Path(config_file).exists():
+            config_file = self.init_flow_config()
         super().__init__(config_file, simulator_name="flow")
 
+    @staticmethod
+    def locate_flow_binary() -> str:
+        """Locate the path for a flow executable.
+
+        Returns the empty string if there is nothing to be found in $PATH."""
+        foundpath = shutil.which("flow")
+        if foundpath is not None:
+            return foundpath
+        return ""
+
+    @staticmethod
+    def init_flow_config() -> str:
+        binary_path = FlowConfig.locate_flow_binary()
+        conf = {
+            "default_version": "default",
+            "versions": {"default": {"scalar": {"executable": binary_path}}},
+        }
+        flow_config_yml = Path("flow_config.yml")
+        flow_config_yml.write_text(yaml.dump(conf), encoding="utf-8")
+        flow_config_path = str(flow_config_yml.absolute())
+        os.environ["FLOW_SITE_CONFIG"] = flow_config_path
+        return flow_config_path
+
 
 class EclrunConfig:
     """This class contains configurations for using the new eclrun binary