Coverage for src / vivarium / _compat / _compat.py: 69%

1"""Backward-compatible import redirects for the vivarium monorepo migration. 

2 

3Intercepts old-style imports (e.g. ``import layered_config_tree``, 

4``from vivarium_public_health.disease import DiseaseModel``) and transparently 

5redirects them to the new ``vivarium.*`` namespace, emitting a DeprecationWarning. 

6 

7Activated at interpreter startup via ``vivarium_compat.pth`` so the hook is in 

8place before any user code runs. 

9 

10To add a redirect when a package migrates, add an entry to ``_REDIRECTS`` and 

11bump the ``vivarium-compat`` version in ``pyproject.toml``. Entries are safe 

12to add *before* the target package is released: if the new module isn't 

13importable, the hook falls back to letting the old on-disk package resolve 

14normally, so installations during the transition window aren't broken. 

15 

16Remove this module once all downstream packages have released versions that use 

17the new import paths and the deprecation period has ended. 

18""" 

19 

20import importlib 

21import importlib.abc 

22import importlib.machinery 

23import sys 

24import warnings 

25from types import ModuleType 

26 

27# Old import root -> new import root. 

28# Entries here are safe to populate ahead of the target package's release: 

29# if the new target isn't installed yet, the hook falls back to the old 

30# package's normal on-disk location (so existing installations during the 

31# transition window keep working). 

32_REDIRECTS: dict[str, str] = { 

33 # Renamed top-level packages 

34 "vivarium_profiling": "vivarium.profiling", 

35 "layered_config_tree": "vivarium.config_tree", 

36 # "vivarium_public_health": "vivarium.public_health", 

37 # "vivarium_cluster_tools": "vivarium.cluster_tools", 

38 # "vivarium_testing_utils": "vivarium.testing_utils", 

39 # "vivarium.examples": "vivarium.core.examples", 

40 # "vivarium.framework": "vivarium.core.framework", 

41 # "vivarium.interface": "vivarium.core.interface", 

42 # "vivarium.component": "vivarium.core.component", 

43 # "vivarium.exceptions": "vivarium.core.exceptions", 

44 # "vivarium.manager": "vivarium.core.manager", 

45 # "vivarium.testing_utilities": "vivarium.core.testing_utilities", 

46 # "vivarium.types": "vivarium.core.types", 

47 # "vivarium_helpers": "vivarium.helpers", 

48 # "risk_distributions": "vivarium.risk_distributions", 

49 # "gbd_mapping": "vivarium.gbd_mapping", 

50} 

51 

52# Tracks which old names are currently being resolved to prevent infinite 

53# recursion if a redirect target somehow re-triggers the same old-name import. 

54_resolving: set[str] = set() 

55 

56 

57def _match(fullname: str) -> tuple[str, str] | None: 

58 """Return (old_prefix, new_prefix) if fullname matches a redirect, else None. 

59 

60 Longer prefixes take precedence so more-specific entries win over broader ones. 

61 """ 

62 for old, new in sorted(_REDIRECTS.items(), key=lambda x: -len(x[0])): 

63 if fullname == old or fullname.startswith(old + "."): 

64 return old, new 

65 return None 

66 

67 

68class _CompatFinder(importlib.abc.MetaPathFinder): 

69 """Meta-path finder that redirects deprecated import paths to new locations.""" 

70 

71 def find_spec( 

72 self, 

73 fullname: str, 

74 path: object, 

75 target: ModuleType | None = None, 

76 ) -> importlib.machinery.ModuleSpec | None: 

77 match = _match(fullname) 

78 if match is None: 

79 return None 

80 

81 old_prefix, new_prefix = match 

82 new_name = new_prefix + fullname[len(old_prefix) :] 

83 

84 # Only warn on first import. After exec_module runs, sys.modules[fullname] 

85 # is set to the real module, so subsequent imports return it directly without 

86 # ever reaching find_spec again. This branch fires only in unusual re-entry 

87 # scenarios (e.g. reload()). 

88 if fullname not in sys.modules: 

89 # stacklevel=2 points into importlib internals rather than the caller's 

90 # import statement - the exact depth is CPython-version-dependent. 

91 # The warning message itself is the actionable part. 

92 warnings.warn( 

93 f"'{fullname}' has moved to '{new_name}'. " 

94 "Update your imports. This redirect will be removed in a future release.", 

95 DeprecationWarning, 

96 stacklevel=2, 

97 ) 

98 # submodule_search_locations is intentionally not set on the spec. CPython's 

99 # import machinery calls exec_module before checking __path__ on any child import, 

100 # and exec_module replaces sys.modules[fullname] with the real module (which already 

101 # has the correct __path__). Setting it to [] would be a no-op at best and misleading 

102 # at worst since we don't know at spec-creation time whether the target is a package. 

103 return importlib.machinery.ModuleSpec( 

104 fullname, _CompatLoader(fullname, new_name) 

105 ) 

106 

107 

108class _CompatLoader(importlib.abc.Loader): 

109 """Loads the real module at the new location and aliases it under the old name.""" 

110 

111 def __init__(self, old_name: str, new_name: str) -> None: 

112 self._old_name = old_name 

113 self._new_name = new_name 

114 

115 def exec_module(self, module: ModuleType) -> None: 

116 if self._old_name in _resolving: 

117 raise ImportError( 

118 f"Circular redirect detected: '{self._old_name}' -> '{self._new_name}'" 

119 ) 

120 _resolving.add(self._old_name) 

121 try: 

122 try: 

123 real = importlib.import_module(self._new_name) 

124 except ModuleNotFoundError: 

125 # FIXME: MIC-7100 Revert when all packages are migrated 

126 # New target isn't installed. Fall back to the old name's actual 

127 # on-disk location so installations during the transition window 

128 # — old package still installed, new package not yet released — 

129 # keep working. The DeprecationWarning was already emitted in 

130 # find_spec(); users will see it whether or not the fallback fires. 

131 real = _import_bypassing_compat(self._old_name) 

132 # Register under the old name so subsequent imports hit sys.modules directly. 

133 sys.modules[self._old_name] = real 

134 # Defensive: covers the case where another import hook holds a direct 

135 # reference to the placeholder module object rather than re-reading sys.modules. 

136 module.__dict__.update(real.__dict__) 

137 # __spec__.name will show the new name (e.g. "vivarium.config_tree"), not the 

138 # old one. This is intentional: sys.modules[old_name] IS real, so its metadata 

139 # correctly describes its actual location. Users inspecting __spec__ after 

140 # migrating their imports will see the right thing. 

141 module.__spec__ = real.__spec__ 

142 finally: 

143 _resolving.discard(self._old_name) 

144 

145 

146def _import_bypassing_compat(name: str) -> ModuleType: 

147 """Import `name` without going through our compat finder. 

148 

149 Used to fall back to a name's real on-disk location when the redirect target 

150 isn't installed. Temporarily removes our finder from sys.meta_path so the 

151 standard PathFinder resolves the name directly. Also clears any placeholder 

152 sys.modules entry the import system set when our find_spec returned a spec. 

153 """ 

154 sys.modules.pop(name, None) 

155 saved: list[tuple[int, _CompatFinder]] = [ 

156 (i, f) for i, f in enumerate(sys.meta_path) if isinstance(f, _CompatFinder) 

157 ] 

158 for _, f in saved: 

159 sys.meta_path.remove(f) 

160 try: 

161 return importlib.import_module(name) 

162 finally: 

163 # Reinsert in original order so any other meta_path entries stay in place. 

164 for i, f in saved: 

165 sys.meta_path.insert(i, f) 

166 

167 

168def install_compat_finder() -> None: 

169 """Install the compat finder into sys.meta_path (idempotent).""" 

170 if not any(isinstance(f, _CompatFinder) for f in sys.meta_path): 

171 sys.meta_path.insert(0, _CompatFinder())