Better change detection on deleted files (Cherry-pick of #23311)#23314
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Better change detection on deleted files (Cherry-pick of #23311)#23314
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There are several longstanding issues on this: #13232 #14975 #17512 #23240 This has historically been intractable because the design of dep inference and of change detection are at odds with each other. A fully robust solution is still somewhat out of reach, but this change provides a general-purpose mechanism that backends can opt in to, and uses that mechanism in the python backend. The result is a substantial yet incremental improvement in the most prominent use case. The limitation of this mechanism is that it can only be used if a backend can infer a likely dependency on a file simply from its path. In Python this is possible because dotted module paths must recapitulate the filesystem path from the source root. But this is not true in general for all languages.
WorkerPants
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benjyw
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May 5, 2026
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There are several longstanding issues on this:
#13232
#14975
#17512
#23240
This has historically been intractable because the
design of dep inference and of change detection
are at odds with each other.
A fully robust solution is still somewhat out of reach,
but this change provides a general-purpose mechanism
that backends can opt in to, and uses that mechanism
in the python backend.
The result is a substantial yet incremental improvement
in the most prominent use case.
The limitation of this mechanism is that it can only
be used if a backend can infer a likely dependency on
a file simply from its path. In Python this is possible because
dotted module paths must recapitulate the filesystem path
from the source root. But this is not true in general for
all languages.