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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__ = ("PexConfigFormatter", ) 

25 

26import os.path 

27 

28from typing import ( 

29 Any, 

30 Optional, 

31 Type, 

32) 

33 

34from lsst.utils import doImport 

35from .file import FileFormatter 

36 

37 

38class PexConfigFormatter(FileFormatter): 

39 """Interface for reading and writing pex.config.Config objects from disk. 

40 """ 

41 extension = ".py" 

42 

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

44 """Read a pex.config.Config instance from the given file. 

45 

46 Parameters 

47 ---------- 

48 path : `str` 

49 Path to use to open the file. 

50 pytype : `class` 

51 Class to use to read the config file. 

52 

53 Returns 

54 ------- 

55 data : `lsst.pex.config.Config` 

56 Instance of class `pytype` read from config file. None 

57 if the file could not be opened. 

58 """ 

59 if pytype is None: 

60 raise RuntimeError("A python type is always required for reading pex_config Config files") 

61 

62 if not os.path.exists(path): 

63 return None 

64 instance = pytype() 

65 # Configs can only be loaded if you use the correct derived type, 

66 # but we can't really store the correct derive type in the StorageClass 

67 # because that"d be a huge proliferation of StorageClasses. 

68 # Instead, we use a bit of a hack: try to load using the base-class 

69 # Config, inspect the exception message to obtain the class we should 

70 # have used, import that, and try it instead. 

71 # TODO: clean this up, somehow. 

72 try: 

73 instance.load(path) 

74 return instance 

75 except AssertionError as err: 

76 msg = str(err) 

77 if not msg.startswith("config is of type"): 

78 raise RuntimeError("Unexpected assertion; cannot infer Config class type.") from err 

79 actualPyTypeStr = msg.split()[-1] 

80 actualPyType = doImport(actualPyTypeStr) 

81 instance = actualPyType() 

82 instance.load(path) 

83 return instance 

84 

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

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

87 

88 Parameters 

89 ---------- 

90 inMemoryDataset : `object` 

91 Object to serialize. 

92 

93 Raises 

94 ------ 

95 Exception 

96 The file could not be written. 

97 """ 

98 inMemoryDataset.save(self.fileDescriptor.location.path)