Adds dump() to scheduler.py -- a pure local .replay file decoder, zero
network I/O. Key finding: pycapnp's from_bytes() does not validate a
message against the schema type you ask it to decode as (trial-decoding
SnapshotEntry bytes as ReplayEvent raises nothing, returns plausible
garbage), ruling out trial-decode-and-catch for message-type
discrimination. Instead reads each message's raw segment-table/
root-pointer framing to extract its (dataWordCount, pointerCount) shape,
computed live from the schema, and matches against the four replay
message types' distinct shapes before decoding. AC 20's stream-ordering
rules (msg 1 = ReplayHeader, msg 2 = SnapshotEntry) are enforced
structurally, not inferred.
Adversarial review reproduced a real (if forward-looking) gap: an actual
modified schema with a shape collision caused an uncaught raw capnp
exception to escape dump(). Closed with a pairwise-distinctness
assertion right after the four shapes are computed, raising a typed
ReplayFileError before any message is decoded if a future schema change
ever makes two shapes collide -- restoring dump()'s own docstring
guarantee unconditionally. New regression test simulates the exact
collision the review found.
201 passed, 3 skipped (up from 188 pre-task).
Rongsong Shen
8034fb6e1f
