By default, detect ocean model based on files in path

docs/developers_guide/quick_start.md

@@ -478,6 +478,11 @@ make <mpas_make_target>
 
 The same applies to MPAS-Seaice except with `mpas-seaice` in the path above.
 
+To set up tasks and suites to use MPAS-Ocean, it should be sufficient to point
+to an MPAS-Ocean build with the `-p` flag to `polaris setup` or
+`polaris suite`.  MPAS-Ocean should automatically be detected.  You can use
+the flag `--model mpas-ocean` to be explicit, though.
+
 (dev-omega-build)=
 
 ### Omega
@@ -526,9 +531,10 @@ location you like.  If you build in a location other than
 relative or absolute path using the `-p` flag when you call `polaris setup` or
 `polaris suite`.
 
-To set up tasks and suites to use Omega, you need to supply `--model=omega`
-to `polaris setup` or `polaris suite`.  Otherwise, it will default to
-MPAS-Ocean.
+As with MPAS-Ocean, to set up tasks and suites to use Omega, it should be
+sufficient to point to an Omega build with the `-p` flag to `polaris setup` or
+`polaris suite`, which should allow Omega to be detected automatically.
+But you can use the flag `--model omega` to indicate this explicitly.
 
 (dev-working-with-polaris)=
 

polaris/ocean/ocean.cfg

@@ -3,8 +3,8 @@
 
 # Options related the ocean component
 [ocean]
-# Which model, MPAS-Ocean or Omega, is used
-model = mpas-ocean
+# Which model, MPAS-Ocean or Omega, is used, or "detect" to auto-detect
+model = detect
 
 # the number of cells per core to aim for
 goal_cells_per_core = 200

polaris/setup.py

@@ -112,9 +112,15 @@ def setup_tasks(
     component = tasks[first_path].component
 
     basic_config = _get_basic_config(
-        config_file, machine, component_path, component, model
+        config_file=config_file,
+        machine=machine,
+        component_path=component_path,
+        component=component,
+        model=model,
     )
 
+    component.configure(basic_config)
+
     provenance.write(work_dir, tasks, config=basic_config)
 
     if clean:
@@ -124,14 +130,11 @@ def setup_tasks(
         print('')
 
     _setup_configs(
-        component,
-        tasks,
-        work_dir,
-        config_file,
-        machine,
-        component_path,
-        copy_executable,
-        model,
+        basic_config=basic_config,
+        component=component,
+        tasks=tasks,
+        work_dir=work_dir,
+        copy_executable=copy_executable,
     )
 
     # do this after _setup_configs() in case tasks mark additional steps
@@ -432,20 +435,15 @@ def _expand_and_mark_cached_steps(tasks, cached_steps):
 
 
 def _setup_configs(
+    basic_config,
     component,
     tasks,
     work_dir,
-    config_file,
-    machine,
-    component_path,
     copy_executable,
-    model,
 ):
     """Set up config parsers for this component"""
 
-    common_config = _get_basic_config(
-        config_file, machine, component_path, component, model
-    )
+    common_config = basic_config.copy()
     if copy_executable:
         common_config.set('setup', 'copy_executable', 'True')
 
@@ -718,8 +716,6 @@ def _get_basic_config(config_file, machine, component_path, component, model):
         exception=False,
     )
 
-    component.configure(config)
-
     # set the component_path path from the command line if provided
     if component_path is not None:
         component_path = os.path.abspath(component_path)

polaris/tasks/ocean/__init__.py

@@ -1,4 +1,5 @@
 import importlib.resources as imp_res
+import os
 from typing import Dict, Union
 
 import xarray as xr
@@ -44,6 +45,10 @@ def configure(self, config):
         """
         section = config['ocean']
         model = section.get('model')
+        if model == 'detect':
+            model = self._detect_model(config)
+            print('Detected ocean model:', model)
+            config.set('ocean', 'model', model)
         configs = {'mpas-ocean': 'mpas_ocean.cfg', 'omega': 'omega.cfg'}
         if model not in configs:
             raise ValueError(f'Unknown ocean model {model} in config options')
@@ -228,6 +233,72 @@ def _read_var_map(self):
         self.mpaso_to_omega_dim_map = nested_dict['dimensions']
         self.mpaso_to_omega_var_map = nested_dict['variables']
 
+    def _detect_model(self, config) -> str:
+        """
+        Detect which ocean model to use
+        """
+        # build config options for each model, so the default component_path
+        # can be read if it hasn't been overridden
+        omega_config = config.copy()
+        omega_config.add_from_package('polaris.ocean', 'omega.cfg')
+        omega_path = omega_config.get('paths', 'component_path')
+
+        mpas_ocean_config = config.copy()
+        mpas_ocean_config.add_from_package('polaris.ocean', 'mpas_ocean.cfg')
+        mpas_ocean_path = mpas_ocean_config.get('paths', 'component_path')
+
+        if self._detect_omega_build(omega_path):
+            return 'omega'
+        elif self._detect_mpas_ocean_build(mpas_ocean_path):
+            return 'mpas-ocean'
+        else:
+            raise ValueError(
+                f'Could not detect ocean model; neither MPAS-Ocean '
+                f'nor Omega appear to be available; '
+                f'searched {omega_path} and {mpas_ocean_path}.'
+            )
+
+    def _detect_omega_build(self, path) -> bool:
+        """
+        Detect if Omega is available
+        """
+        required_files = [
+            'configs/Default.yml',
+            'src/omega.exe',
+        ]
+        path = os.path.abspath(path)
+
+        all_found = True
+        for required_file in required_files:
+            if not os.path.exists(os.path.join(path, required_file)):
+                all_found = False
+                break
+        return all_found
+
+    def _detect_mpas_ocean_build(self, path) -> bool:
+        """
+        Detect if MPAS-Ocean is available
+
+        Returns
+        -------
+        is_mpas_ocean : bool
+            True if MPAS-Ocean appears to be available, False otherwise
+        """
+        required_files = [
+            'default_inputs/namelist.ocean.forward',
+            'default_inputs/streams.ocean.forward',
+            'src/Registry_processed.xml',
+            'ocean_model',
+        ]
+        path = os.path.abspath(path)
+
+        all_found = True
+        for required_file in required_files:
+            if not os.path.exists(os.path.join(path, required_file)):
+                all_found = False
+                break
+        return all_found
+
 
 # create a single module-level instance available to other components
 ocean = Ocean()