Coverage for python/lsst/daf/butler/formatters/json.py: 81%

33 statements  

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1# This file is part of daf_butler. 

2# 

3# Developed for the LSST Data Management System. 

4# This product includes software developed by the LSST Project 

5# (http://www.lsst.org). 

6# See the COPYRIGHT file at the top-level directory of this distribution 

7# for details of code ownership. 

8# 

9# This software is dual licensed under the GNU General Public License and also 

10# under a 3-clause BSD license. Recipients may choose which of these licenses 

11# to use; please see the files gpl-3.0.txt and/or bsd_license.txt, 

12# respectively. If you choose the GPL option then the following text applies 

13# (but note that there is still no warranty even if you opt for BSD instead): 

14# 

15# This program is free software: you can redistribute it and/or modify 

16# it under the terms of the GNU General Public License as published by 

17# the Free Software Foundation, either version 3 of the License, or 

18# (at your option) any later version. 

19# 

20# This program is distributed in the hope that it will be useful, 

21# but WITHOUT ANY WARRANTY; without even the implied warranty of 

22# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

23# GNU General Public License for more details. 

24# 

25# You should have received a copy of the GNU General Public License 

26# along with this program. If not, see <http://www.gnu.org/licenses/>. 

27 

28from __future__ import annotations 

29 

30__all__ = ("JsonFormatter",) 

31 

32import contextlib 

33import dataclasses 

34import json 

35from typing import Any 

36 

37from .file import FileFormatter 

38 

39 

40class JsonFormatter(FileFormatter): 

41 """Formatter implementation for JSON files.""" 

42 

43 extension = ".json" 

44 

45 unsupportedParameters = None 

46 """This formatter does not support any parameters (`frozenset`)""" 

47 

48 def _readFile(self, path: str, pytype: type[Any] | None = None) -> Any: 

49 """Read a file from the path in JSON format. 

50 

51 Parameters 

52 ---------- 

53 path : `str` 

54 Path to use to open JSON format file. 

55 pytype : `class`, optional 

56 Not used by this implementation. 

57 

58 Returns 

59 ------- 

60 data : `object` 

61 Data as Python object read from JSON file. 

62 """ 

63 with open(path, "rb") as fd: 

64 data = self._fromBytes(fd.read(), pytype) 

65 

66 return data 

67 

68 def _writeFile(self, inMemoryDataset: Any) -> None: 

69 """Write the in memory dataset to file on disk. 

70 

71 Will look for `_asdict()` method to aid JSON serialization, following 

72 the approach of the simplejson module. 

73 

74 Parameters 

75 ---------- 

76 inMemoryDataset : `object` 

77 Object to serialize. 

78 

79 Raises 

80 ------ 

81 Exception 

82 The file could not be written. 

83 """ 

84 self.fileDescriptor.location.uri.write(self._toBytes(inMemoryDataset)) 

85 

86 def _fromBytes(self, serializedDataset: bytes, pytype: type[Any] | None = None) -> Any: 

87 """Read the bytes object as a python object. 

88 

89 Parameters 

90 ---------- 

91 serializedDataset : `bytes` 

92 Bytes object to unserialize. 

93 pytype : `class`, optional 

94 Not used by this implementation. 

95 

96 Returns 

97 ------- 

98 inMemoryDataset : `object` 

99 The requested data as a Python object or None if the string could 

100 not be read. 

101 """ 

102 try: 

103 data = json.loads(serializedDataset) 

104 except json.JSONDecodeError: 

105 data = None 

106 

107 return data 

108 

109 def _toBytes(self, inMemoryDataset: Any) -> bytes: 

110 """Write the in memory dataset to a bytestring. 

111 

112 Parameters 

113 ---------- 

114 inMemoryDataset : `object` 

115 Object to serialize 

116 

117 Returns 

118 ------- 

119 serializedDataset : `bytes` 

120 bytes representing the serialized dataset. 

121 

122 Raises 

123 ------ 

124 Exception 

125 The object could not be serialized. 

126 """ 

127 # Try different standardized methods for native json. 

128 # For example, Pydantic models have a .model_dump_json method. 

129 # v1 models without compatibility layer will need .json() 

130 with contextlib.suppress(AttributeError): 

131 return inMemoryDataset.model_dump_json().encode() 

132 with contextlib.suppress(AttributeError): 132 ↛ exitline 132 didn't return from function '_toBytes', because the return on line 133 wasn't executed

133 return inMemoryDataset.json().encode() 

134 

135 if dataclasses.is_dataclass(inMemoryDataset): 

136 inMemoryDataset = dataclasses.asdict(inMemoryDataset) 

137 elif hasattr(inMemoryDataset, "_asdict"): 

138 inMemoryDataset = inMemoryDataset._asdict() 

139 return json.dumps(inMemoryDataset, ensure_ascii=False).encode()