+
+
+ def load_sub_configuration(self, filename: StrPath,
+ config: Optional[str] = None) -> Any:
+ """ Load additional configuration from a file. `filename` is the name
+ of the configuration file. The file is first searched in the
+ project directory and then in the global settings dirctory.
+
+ If `config` is set, then the name of the configuration file can
+ be additionally given through a .env configuration option. When
+ the option is set, then the file will be exclusively loaded as set:
+ if the name is an absolute path, the file name is taken as is,
+ if the name is relative, it is taken to be relative to the
+ project directory.
+
+ The format of the file is determined from the filename suffix.
+ Currently only files with extension '.yaml' are supported.
+
+ YAML files support a special '!include' construct. When the
+ directive is given, the value is taken to be a filename, the file
+ is loaded using this function and added at the position in the
+ configuration tree.
+ """
+ configfile = self.find_config_file(filename, config)
+
+ if str(configfile) in CONFIG_CACHE:
+ return CONFIG_CACHE[str(configfile)]
+
+ if configfile.suffix in ('.yaml', '.yml'):
+ result = self._load_from_yaml(configfile)
+ elif configfile.suffix == '.json':
+ with configfile.open('r', encoding='utf-8') as cfg:
+ result = json.load(cfg)
+ else:
+ raise UsageError(f"Config file '{configfile}' has unknown format.")
+
+ CONFIG_CACHE[str(configfile)] = result
+ return result
+
+
+ def find_config_file(self, filename: StrPath,
+ config: Optional[str] = None) -> Path:
+ """ Resolve the location of a configuration file given a filename and
+ an optional configuration option with the file name.
+ Raises a UsageError when the file cannot be found or is not
+ a regular file.
+ """
+ if config is not None:
+ cfg_value = getattr(self, config)
+ if cfg_value:
+ cfg_filename = Path(cfg_value)
+
+ if cfg_filename.is_absolute():
+ cfg_filename = cfg_filename.resolve()
+
+ if not cfg_filename.is_file():
+ LOG.fatal("Cannot find config file '%s'.", cfg_filename)
+ raise UsageError("Config file not found.")
+
+ return cfg_filename
+
+ filename = cfg_filename
+
+
+ search_paths = [self.project_dir, self.config_dir]
+ for path in search_paths:
+ if path is not None and (path / filename).is_file():
+ return path / filename
+
+ LOG.fatal("Configuration file '%s' not found.\nDirectories searched: %s",
+ filename, search_paths)
+ raise UsageError("Config file not found.")
+
+
+ def _load_from_yaml(self, cfgfile: Path) -> Any:
+ """ Load a YAML configuration file. This installs a special handler that
+ allows to include other YAML files using the '!include' operator.
+ """
+ yaml.add_constructor('!include', self._yaml_include_representer,
+ Loader=yaml.SafeLoader)
+ return yaml.safe_load(cfgfile.read_text(encoding='utf-8'))
+
+
+ def _yaml_include_representer(self, loader: Any, node: yaml.Node) -> Any:
+ """ Handler for the '!include' operator in YAML files.
+
+ When the filename is relative, then the file is first searched in the
+ project directory and then in the global settings dirctory.
+ """
+ fname = loader.construct_scalar(node)
+
+ if Path(fname).is_absolute():
+ configfile = Path(fname)
+ else:
+ configfile = self.find_config_file(loader.construct_scalar(node))
+
+ if configfile.suffix != '.yaml':
+ LOG.fatal("Format error while reading '%s': only YAML format supported.",
+ configfile)
+ raise UsageError("Cannot handle config file format.")
+
+ return yaml.safe_load(configfile.read_text(encoding='utf-8'))