Coverage for python/lsst/daf/butler/formatters/yaml.py: 29%

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

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

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

12# (at your option) any later version. 

13# 

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

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

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

17# GNU General Public License for more details. 

18# 

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

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

21 

22from __future__ import annotations 

23 

24__all__ = ("YamlFormatter",) 

25 

26import builtins 

27import dataclasses 

28from typing import TYPE_CHECKING, Any, Optional, Type 

29 

30import yaml 

31 

32from .file import FileFormatter 

33 

34if TYPE_CHECKING: 34 ↛ 35line 34 didn't jump to line 35, because the condition on line 34 was never true

35 from lsst.daf.butler import StorageClass 

36 

37 

38class YamlFormatter(FileFormatter): 

39 """Formatter implementation for YAML files.""" 

40 

41 extension = ".yaml" 

42 

43 unsupportedParameters = None 

44 """This formatter does not support any parameters""" 

45 

46 supportedWriteParameters = frozenset({"unsafe_dump"}) 

47 """Allow the normal yaml.dump to be used to write the YAML. Use this 

48 if you know that your class has registered representers.""" 

49 

50 def _readFile(self, path: str, pytype: Type[Any] = None) -> Any: 

51 """Read a file from the path in YAML format. 

52 

53 Parameters 

54 ---------- 

55 path : `str` 

56 Path to use to open YAML format file. 

57 pytype : `class`, optional 

58 Not used by this implementation. 

59 

60 Returns 

61 ------- 

62 data : `object` 

63 Either data as Python object read from YAML file, or None 

64 if the file could not be opened. 

65 

66 Notes 

67 ----- 

68 The `~yaml.SafeLoader` is used when parsing the YAML file. 

69 """ 

70 try: 

71 with open(path, "rb") as fd: 

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

73 except FileNotFoundError: 

74 data = None 

75 

76 return data 

77 

78 def _fromBytes(self, serializedDataset: bytes, pytype: Optional[Type[Any]] = None) -> Any: 

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

80 

81 Parameters 

82 ---------- 

83 serializedDataset : `bytes` 

84 Bytes object to unserialize. 

85 pytype : `class`, optional 

86 Not used by this implementation. 

87 

88 Returns 

89 ------- 

90 inMemoryDataset : `object` 

91 The requested data as an object, or None if the string could 

92 not be read. 

93 

94 Notes 

95 ----- 

96 The `~yaml.SafeLoader` is used when parsing the YAML. 

97 """ 

98 data = yaml.safe_load(serializedDataset) 

99 

100 try: 

101 data = data.exportAsDict() 

102 except AttributeError: 

103 pass 

104 return data 

105 

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

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

108 

109 Will look for `_asdict()` method to aid YAML serialization, following 

110 the approach of the simplejson module. The `dict` will be passed 

111 to the relevant constructor on read. 

112 

113 Parameters 

114 ---------- 

115 inMemoryDataset : `object` 

116 Object to serialize. 

117 

118 Raises 

119 ------ 

120 Exception 

121 The file could not be written. 

122 

123 Notes 

124 ----- 

125 The `~yaml.SafeDumper` is used when generating the YAML serialization. 

126 This will fail for data structures that have complex python classes 

127 without a registered YAML representer. 

128 """ 

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

130 

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

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

133 

134 Will look for `_asdict()` method to aid YAML serialization, following 

135 the approach of the simplejson module. The `dict` will be passed 

136 to the relevant constructor on read. 

137 

138 Parameters 

139 ---------- 

140 inMemoryDataset : `object` 

141 Object to serialize 

142 

143 Returns 

144 ------- 

145 serializedDataset : `bytes` 

146 YAML string encoded to bytes. 

147 

148 Raises 

149 ------ 

150 Exception 

151 The object could not be serialized. 

152 

153 Notes 

154 ----- 

155 The `~yaml.SafeDumper` is used when generating the YAML serialization. 

156 This will fail for data structures that have complex python classes 

157 without a registered YAML representer. 

158 """ 

159 if dataclasses.is_dataclass(inMemoryDataset): 

160 inMemoryDataset = dataclasses.asdict(inMemoryDataset) 

161 elif hasattr(inMemoryDataset, "_asdict"): 

162 inMemoryDataset = inMemoryDataset._asdict() 

163 unsafe_dump = self.writeParameters.get("unsafe_dump", False) 

164 if unsafe_dump: 

165 serialized = yaml.dump(inMemoryDataset) 

166 else: 

167 serialized = yaml.safe_dump(inMemoryDataset) 

168 return serialized.encode() 

169 

170 def _coerceType( 

171 self, inMemoryDataset: Any, writeStorageClass: StorageClass, readStorageClass: StorageClass 

172 ) -> Any: 

173 """Coerce the supplied inMemoryDataset to the correct python type. 

174 

175 Parameters 

176 ---------- 

177 inMemoryDataset : `object` 

178 Object to coerce to expected type. 

179 writeStorageClass : `StorageClass` 

180 Storage class used to serialize this data. 

181 readStorageClass : `StorageClass` 

182 Storage class requested as the outcome. 

183 

184 Returns 

185 ------- 

186 inMemoryDataset : `object` 

187 Object of expected type ``readStorageClass.pytype``. 

188 """ 

189 if inMemoryDataset is not None and not hasattr(builtins, readStorageClass.pytype.__name__): 

190 if readStorageClass.isComposite(): 

191 inMemoryDataset = readStorageClass.delegate().assemble( 

192 inMemoryDataset, pytype=readStorageClass.pytype 

193 ) 

194 return readStorageClass.coerce_type(inMemoryDataset) 

195 elif not isinstance(inMemoryDataset, readStorageClass.pytype): 

196 if not isinstance(inMemoryDataset, writeStorageClass.pytype): 

197 # This does not look like the written type or the required 

198 # type. Try to cast it to the written type and then coerce 

199 # to requested type. 

200 if dataclasses.is_dataclass(writeStorageClass.pytype): 

201 # dataclasses accept key/value parameters. 

202 inMemoryDataset = writeStorageClass.pytype(**inMemoryDataset) 

203 else: 

204 # Hope that we can pass the arguments in directly. 

205 inMemoryDataset = writeStorageClass.pytype(inMemoryDataset) 

206 # Coerce to the read storage class if necessary. 

207 inMemoryDataset = readStorageClass.coerce_type(inMemoryDataset) 

208 return inMemoryDataset