Fix and document clearsky_model for ModelChain (#1924)

* add note about clearsky_model

* whatsnew

* pass clearsky_model to get_clearsky

* add bug fix note

* test for correct argument

* test for correct argument

* test for correct argument

docs/sphinx/source/whatsnew/v0.10.3.rst

@@ -22,6 +22,8 @@ Bug fixes
   :py:func:`pvlib.iotools.get_cams` (:issue:`1799`, :pull:`1905`)
 * Fix mapping of the dew point column to ``temp_dew`` when ``map_variables``
   is True in :py:func:`pvlib.iotools.get_psm3`. (:pull:`1920`)
+* Fix :py:class:`pvlib.modelchain.ModelChain` to use attribute `clearsky_model`
+  (:pull:`1924`)
 
 Testing
 ~~~~~~~
@@ -34,6 +36,7 @@ Documentation
 * Fixed a plotting issue in the IV curve gallery example (:pull:`1895`)
 * Added two examples to demonstrate reverse transposition (:pull:`1907`)
 * Fixed `detect_clearsky` example in `clearsky.rst` (:issue:`1914`)
+* Clarified purpose of `ModelChain.clearsky_model` (:pull:`1924`)
 
 
 Requirements
@@ -52,3 +55,4 @@ Contributors
 * :ghuser:`matsuobasho`
 * Harry Jack (:ghuser:`harry-solcast`)
 * Kevin Anderson (:ghuser:`kandersolar`)
+* Cliff Hansen (:ghuser:`cwhanse`)

pvlib/modelchain.py

@@ -460,7 +460,8 @@ class ModelChain:
         the physical location at which to evaluate the model.
 
     clearsky_model : str, default 'ineichen'
-        Passed to location.get_clearsky.
+        Passed to location.get_clearsky. Only used when DNI is not found in
+        the weather inputs.
 
     transposition_model : str, default 'haydavies'
         Passed to system.get_irradiance.
@@ -1354,7 +1355,8 @@ def _complete_irradiance(self, weather):
                    "https://github.com/pvlib/pvlib-python \n")
         if {'ghi', 'dhi'} <= icolumns and 'dni' not in icolumns:
             clearsky = self.location.get_clearsky(
-                weather.index, solar_position=self.results.solar_position)
+                weather.index, model=self.clearsky_model,
+                solar_position=self.results.solar_position)
             complete_irrad_df = pvlib.irradiance.complete_irradiance(
                 solar_zenith=self.results.solar_position.zenith,
                 ghi=weather.ghi,

pvlib/tests/test_modelchain.py

@@ -1847,7 +1847,7 @@ def test_complete_irradiance_clean_run(sapm_dc_snl_ac_system, location):
                         pd.Series([9, 5], index=times, name='ghi'))
 
 
-def test_complete_irradiance(sapm_dc_snl_ac_system, location):
+def test_complete_irradiance(sapm_dc_snl_ac_system, location, mocker):
     """Check calculations"""
     mc = ModelChain(sapm_dc_snl_ac_system, location)
     times = pd.date_range('2010-07-05 7:00:00-0700', periods=2, freq='H')
@@ -1867,7 +1867,11 @@ def test_complete_irradiance(sapm_dc_snl_ac_system, location):
                         pd.Series([372.103976116, 497.087579068],
                                   index=times, name='ghi'))
 
+    # check that clearsky_model is used correctly
+    m_ineichen = mocker.spy(location, 'get_clearsky')
     mc.complete_irradiance(i[['dhi', 'ghi']])
+    assert m_ineichen.call_count == 1
+    assert m_ineichen.call_args[1]['model'] == 'ineichen'
     assert_series_equal(mc.results.weather['dni'],
                         pd.Series([49.756966, 62.153947],
                                   index=times, name='dni'))