pferd/PFERD/report.py

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from pathlib import PurePath
from typing import Set
class MarkDuplicateError(Exception):
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"""
Tried to mark a file that was already marked.
"""
def __init__(self, path: PurePath):
super().__init__(f"A previous file already used path {path}")
self.path = path
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class MarkConflictError(Exception):
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"""
Marking the path would have caused a conflict.
A conflict can have two reasons: Either the new file has the same path as
the parent directory of a known file, or a parent directory of the new file
has the same path as a known file. In either case, adding the new file
would require a file and a directory to share the same path, which is
usually not possible.
"""
def __init__(self, path: PurePath, collides_with: PurePath):
super().__init__(f"File at {path} collides with previous file at {collides_with}")
self.path = path
self.collides_with = collides_with
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# TODO Use PurePath.is_relative_to when updating to 3.9
def is_relative_to(a: PurePath, b: PurePath) -> bool:
try:
a.relative_to(b)
return True
except ValueError:
return False
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class Report:
"""
A report of a synchronization. Includes all files found by the crawler, as
well as the set of changes made to local files.
"""
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def __init__(self) -> None:
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self.reserved_files: Set[PurePath] = set()
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self.known_files: Set[PurePath] = set()
self.new_files: Set[PurePath] = set()
self.changed_files: Set[PurePath] = set()
self.deleted_files: Set[PurePath] = set()
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def mark_reserved(self, path: PurePath) -> None:
self.reserved_files.add(path)
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def mark(self, path: PurePath) -> None:
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"""
Mark a previously unknown file as known.
May throw a MarkDuplicateError or a MarkConflictError. For more detail,
see the respective exception's docstring.
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"""
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for other in self.marked:
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if path == other:
raise MarkDuplicateError(path)
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if is_relative_to(path, other) or is_relative_to(other, path):
raise MarkConflictError(path, other)
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self.known_files.add(path)
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@property
def marked(self) -> Set[PurePath]:
return self.known_files | self.reserved_files
def is_marked(self, path: PurePath) -> bool:
return path in self.marked
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def add_file(self, path: PurePath) -> None:
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"""
Unlike mark(), this function accepts any paths.
"""
self.new_files.add(path)
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def change_file(self, path: PurePath) -> None:
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"""
Unlike mark(), this function accepts any paths.
"""
self.changed_files.add(path)
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def delete_file(self, path: PurePath) -> None:
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"""
Unlike mark(), this function accepts any paths.
"""
self.deleted_files.add(path)