Templating files with Jinja

esm_runscripts supports jinja templating. This is desirable because some times we might want that esm_runcripts “edits” some source files based on parameters defined in the configuration yamls or in its current scope.

For example, in the following domain_def.xml file:

<domain_definition>
<!-- Definition of the native domain of the model -->
<domain id="reduced_gaussian" long_name="reduced Gaussian grid" type="gaussian" />

<!-- Definition of regular Gaussian domains -->
<domain_group id="regular_domains" type="rectilinear" >
   <domain id="regular" long_name="regular grid" ni_glo="{{xios.ni_glo}}" nj_glo="{{xios.nj_glo}}" >
      <generate_rectilinear_domain />
      <interpolate_domain order="1" write_weight="true" />
   </domain>
</domain_group>
</domain_definition>

we want that ni_glo and nj_glo get the values from the parameters xios.ni_glo and xios.nj_glo defined in esm_tools/configs/components/xios/xios.yaml.

This is achieved in esm_runscripts by:

Having a source file where it’s name finishes with .j2, and that uses the syntax in the example above (including the ESM-Tools parameters to be substituted within double curly braces {{ }}), or using any other jinja syntax (read more about jinja syntax in the jinja’s documentation).
Including that file as a source in any of the configuration yamls involved in the simulation. For example, to use the namelists/oifs/43r3/xios/domain_def.xml.j2 template to generate the domain_def.xml file, we would include it in the esm_tools/configs/components/xios/xios.yaml as follows (the same way we include any file that must be copied/moved/linked to the working directory, i.e., File Dictionaries):
```
config_sources:
    domain_def: ${xml_dir}/domain_def.xml.j2

config_in_work:
    domain_def: domain_def.xml
```

Warning

If a template’s name does not end with .j2, it will be copied as is, without any substitution.

Note

As with any other file dictionary, you can ommit the target (in this case config_in_work.domain_def) and the file will be copied to the target directory with the same name as the source file, except that for jinja files, the .j2 will be removed.