The After Effects stagger idiom
id = thisProperty.propertyGroup(2).propertyIndex;
failed with "not a callable function": the expression object model had
no propertyGroup() and property groups had no propertyIndex.
- Property.propertyGroup(countUp = 1) and PropertyGroup.propertyGroup()
return the group countUp levels up; from a top-level group they reach
the layer. A count below 1, not a number, or above the layer is an
error naming propertyGroup, never a crash.
- PropertyGroup.propertyIndex: the group's 1-based index among its
siblings (Child requests now carry it).
- One new host request (Ancestor) walks up from the node's full uid
path, so it also works for the property being evaluated.
- Tests for the stagger expression, effect parameters, reaching the
layer, other layers' properties and groups and out-of-range counts;
the fuzzer seeds and tokens include the new members.
fanning_out_reads_stop_at_a_budget expects the run-count error, but under heavy load
the 5 s wall-clock budget could fire first (different error). Add a test-only
per-thread time limit and lift it in that test. Wall-clock assertions in the other
new tests are now only generous hang guards (>=10x), the fuzzer's hang deadline is
24x MAX_TIME and the perf bound is 10x looser.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Problem: expression text is input we don't control, and nothing fuzzed the
expression parser and evaluator. A seeded mutation fuzzer found stack
overflows (a few hundred `?:`/`=>`/`if`, a few thousand `.`/`<`/`()` links,
75 nested template substitutions or regex groups, a chain inside one
template), hangs (an expression reading its own layer's transform nested
2^16 times; fanning-out reads; 10M-iteration loops re-run per read; loops
calling looping functions), an i64 overflow panic in wiggle noise, and NaN
path vertices tripping the rasterizer's clipping assertion.
Fix: a dependency-free seeded fuzzer (crates/expr/src/tests/fuzz.rs: real
AE-style seeds, char/token mutations, worker thread with a 2 MiB stack,
catch_unwind, deadline, env vars for long runs); a weighted nesting
estimate covering chains without brackets and template/regex insides;
cycle detection per (property, time, text); a per-evaluation budget of
20 000 script runs and 5 s (runs are interrupted through boa's budgeted
evaluation; native only); loop limit 1M; wrapping noise lattice indices;
non-finite path results rejected. Each fix has a regression test.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Gert Pellin