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"""Manager to read and modify config data in JSON files.
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"""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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import errno
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import io
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import json
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import os
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from traitlets.config import LoggingConfigurable
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from IPython.utils.py3compat import PY3
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from traitlets.traitlets import Unicode
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def recursive_update(target, new):
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"""Recursively update one dictionary using another.
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None values will delete their keys.
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"""
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for k, v in new.items():
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if isinstance(v, dict):
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if k not in target:
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target[k] = {}
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recursive_update(target[k], v)
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if not target[k]:
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# Prune empty subdicts
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del target[k]
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elif v is None:
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target.pop(k, None)
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else:
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target[k] = v
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class BaseJSONConfigManager(LoggingConfigurable):
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"""General JSON config manager
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Deals with persisting/storing config in a json file
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"""
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config_dir = Unicode('.')
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def ensure_config_dir_exists(self):
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try:
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os.mkdir(self.config_dir, 0o755)
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except OSError as e:
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if e.errno != errno.EEXIST:
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raise
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def file_name(self, section_name):
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return os.path.join(self.config_dir, section_name+'.json')
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def get(self, section_name):
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"""Retrieve the config data for the specified section.
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Returns the data as a dictionary, or an empty dictionary if the file
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doesn't exist.
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"""
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filename = self.file_name(section_name)
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if os.path.isfile(filename):
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with io.open(filename, encoding='utf-8') as f:
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return json.load(f)
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else:
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return {}
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def set(self, section_name, data):
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"""Store the given config data.
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"""
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filename = self.file_name(section_name)
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self.ensure_config_dir_exists()
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if PY3:
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f = io.open(filename, 'w', encoding='utf-8')
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else:
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f = open(filename, 'wb')
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with f:
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json.dump(data, f, indent=2)
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def update(self, section_name, new_data):
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"""Modify the config section by recursively updating it with new_data.
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Returns the modified config data as a dictionary.
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"""
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data = self.get(section_name)
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recursive_update(data, new_data)
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self.set(section_name, data)
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return data
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