Add basic support for variable mappings

.circleci/config.yml

@@ -47,6 +47,7 @@ jobs:
       - coverage-reporter/send_report:
           coverage-reports: 'test-reports/coverage.xml'
           project-token: $CODACY_PROJECT_TOKEN
+          skip: true  # skip if project-token is not defined (i.e. on a fork)
 
   install:
     # Test installation

doc/develop/fixing_data.rst

@@ -353,3 +353,19 @@ For example for monthly data, place the files in the ``/Tier3/MSWEP/latestversio
   For monthly data (V220), the data must be postfixed with the date, i.e. rename ``global_monthly_050deg.nc`` to ``global_monthly_050deg_197901-201710.nc``
 
 For more info: http://www.gloh2o.org/
+
+.. _extra-facets-fixes:
+
+Use of extra facets in fixes
+============================
+In fixes, extra facets can be used to mold data into the form required by the
+applicable standard. For example, if the input data is part of an observational
+product that delivers surface temperature with a variable name of `t2m` inside a
+file named `2m_temperature_1950_monthly.nc`, but the same variable is called
+`tas` in the applicable standard, a fix can be created that reads the original
+variable from the correct file, and provides a renamed variable to the rest of
+the processing chain.
+
+Normally, the applicable standard for variables is CMIP6.
+
+For more details, refer to existing uses of this feature as examples.

doc/quickstart/configure.rst

@@ -320,3 +320,73 @@ following documentation section:
 
 These four items here are named people, references and projects listed in the
 ``config-references.yml`` file.
+
+.. _extra_facets:
+
+Extra Facets
+============
+
+Sometimes it is useful to provide extra information for the loading of data,
+particularly in the case of native model data, or observational or other data,
+that generally follows the established standards, but is not part of the big
+supported projects like CMIP, CORDEX, obs4MIPs.
+
+To support this, we provide the extra facets facilities. Facets are the
+key-value pairs described in :ref:`Datasets`. Extra facets allows for the
+addition of more details per project, dataset, mip table, and variable name.
+
+More precisely, one can provide this information in an extra yaml file, named
+`{project}-something.yml`, where `{project}` corresponds to the project as used
+by ESMValTool in :ref:`Datasets` and "something" is arbitrary.
+
+Format of the extra facets files
+--------------------------------
+The extra facets are given in a yaml file, whose file name identifies the
+project. Inside the file there is a hierarchy of nested dictionaries with the
+following levels. At the top there is the `dataset` facet, followed by the `mip`
+table, and finally the `short_name`. The leaf dictionary placed here gives the
+extra facets that will be made available to data finder and the fix
+infrastructure. The following example illustrates the concept.
+
+.. _extra-facets-example-1:
+
+.. code-block:: yaml
+   :caption: Extra facet example file `native6-era5.yml`
+
+   ERA5:
+     Amon:
+       tas: {source_var_name: "t2m", cds_var_name: "2m_temperature"}
+
+
+Location of the extra facets files
+----------------------------------
+Extra facets files can be placed in several different places. When we use them
+to support a particular use-case within the ESMValTool project, they will be
+provided in the sub-folder `extra_facets` inside the package
+`esmvalcore._config`. If they are used from the user side, they can be either
+placed in `~/.esmvaltool/extra_facets` or in any other directory of the users
+choosing. In that case this directory must be added to the `config-user.yml`
+file under the `extra_facets_dir` setting, which can take a single directory or
+a list of directories.
+
+The order in which the directories are searched is
+
+1. The internal directory `esmvalcore._config/extra_facets`
+2. The default user directory `~/.esmvaltool/extra_facets`
+3. The custom user directories in the order in which they are given in
+   `config-user.yml`.
+
+The extra facets files within each of these directories are processed in
+lexicographical order according to their file name.
+
+In all cases it is allowed to supersede information from earlier files in later
+files. This makes it possible for the user to effectively override even internal
+default facets, for example to deal with local particularities in the data
+handling.
+
+Use of extra facets
+-------------------
+For extra facets to be useful, the information that they provide must be
+applied. There are fundamentally two places where this comes into play. One is
+:ref:`the datafinder<extra-facets-data-finder>`, the other are
+:ref:`fixes<extra-facets-fixes>`.

doc/quickstart/find_data.rst

@@ -303,3 +303,33 @@ flexible concatenation between two cubes, depending on the particular setup:
 Note that two cube concatenation is the base operation of an iterative process of reducing multiple cubes
 from multiple data segments via cube concatenation ie if there is no time-overlapping data, the
 cubes concatenation is performed in one step.
+
+.. _extra-facets-data-finder:
+
+Use of extra facets in the datafinder
+=====================================
+Extra facets can be used to locate data files within the datafinder
+framework. This is useful to build paths for directory structures and file names
+that follow a different system than the established DRS for, e.g. CMIP.
+A common application is the location of variables in multi-variable files as
+often found in climate models' native output formats.
+
+Another use case is files that use different names for variables in their
+file name than for the netCDF4 variable name.
+
+To apply the extra facets for this purpose, simply use the corresponding tag in
+the applicable DRS inside the `config-developer.yml` file. For example, given
+the extra facets in :ref:`extra-facets-example-1`, one might write the
+following.
+
+.. _extra-facets-example-2:
+
+.. code-block:: yaml
+   :caption: Example drs use in `config-developer.yml`
+
+   native6:
+     input_file:
+       default: '{name_in_filename}*.nc'
+
+The same replacement mechanism can be employed everywhere where tags can be
+used, particularly in `input_dir` and `input_file`.

doc/requirements.txt

@@ -1,6 +1,7 @@
 autodocsumm
 dask[array]
 fiona
+importlib_resources
 jinja2
 netCDF4
 numpy

esmvalcore/_config/__init__.py

@@ -3,6 +3,7 @@
     get_activity,
     get_institutes,
     get_project_config,
+    get_extra_facets,
     load_config_developer,
     read_config_developer_file,
     read_config_user_file,
@@ -14,6 +15,7 @@
     'read_config_user_file',
     'read_config_developer_file',
     'load_config_developer',
+    'get_extra_facets',
     'get_project_config',
     'get_institutes',
     'get_activity',

esmvalcore/_config/_config.py

@@ -1,8 +1,11 @@
 """Functions dealing with config-user.yml / config-developer.yml."""
+import collections.abc
 import datetime
 import logging
 import os
+import sys
 import warnings
+from functools import lru_cache
 from pathlib import Path
 
 import yaml
@@ -13,6 +16,46 @@
 
 CFG = {}
 
+if sys.version_info[:2] >= (3, 9):
+    # pylint: disable=no-name-in-module
+    from importlib.resources import files as importlib_files
+else:
+    from importlib_resources import files as importlib_files
+
+
+def _deep_update(dictionary, update):
+    for key, value in update.items():
+        if isinstance(value, collections.abc.Mapping):
+            dictionary[key] = _deep_update(dictionary.get(key, {}), value)
+        else:
+            dictionary[key] = value
+    return dictionary
+
+
+@lru_cache
+def _load_extra_facets(project, extra_facets_dir):
+    config = {}
+    config_paths = [
+        importlib_files("esmvalcore._config") / "extra_facets",
+        Path.home() / ".esmvaltool" / "extra_facets",
+    ]
+    config_paths.extend([Path(p) for p in extra_facets_dir])
+    for config_path in config_paths:
+        config_file_paths = config_path.glob(f"{project.lower()}-*.yml")
+        for config_file_path in sorted(config_file_paths):
+            logger.debug("Loading extra facets from %s", config_file_path)
+            with config_file_path.open() as config_file:
+                config_piece = yaml.safe_load(config_file)
+            if config_piece:
+                _deep_update(config, config_piece)
+    return config
+
+
+def get_extra_facets(project, dataset, mip, short_name, extra_facets_dir):
+    """Read configuration files with additional variable information."""
+    project_details = _load_extra_facets(project, extra_facets_dir)
+    return project_details.get(dataset, {}).get(mip, {}).get(short_name, {})
+
 
 def read_config_user_file(config_file, folder_name, options=None):
     """Read config user file and store settings in a dictionary."""
@@ -61,6 +104,7 @@ def read_config_user_file(config_file, folder_name, options=None):
         'output_file_type': 'png',
         'output_dir': 'esmvaltool_output',
         'auxiliary_data_dir': 'auxiliary_data',
+        'extra_facets_dir': tuple(),
         'save_intermediary_cubes': False,
         'remove_preproc_dir': True,
         'max_parallel_tasks': None,
@@ -83,6 +127,12 @@ def read_config_user_file(config_file, folder_name, options=None):
     cfg['output_dir'] = _normalize_path(cfg['output_dir'])
     cfg['auxiliary_data_dir'] = _normalize_path(cfg['auxiliary_data_dir'])
 
+    if isinstance(cfg['extra_facets_dir'], str):
+        cfg['extra_facets_dir'] = (_normalize_path(cfg['extra_facets_dir']), )
+    else:
+        cfg['extra_facets_dir'] = tuple(
+            _normalize_path(p) for p in cfg['extra_facets_dir'])
+
     cfg['config_developer_file'] = _normalize_path(
         cfg['config_developer_file'])