Fix invalid vars#4827
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`mtkcompile`'s zero-variable elimination moves variables with trivial
dynamics (e.g. `D(x) ~ 0`) out of the unknowns, rewriting them as an
observed polynomial in the independent variable with a `missing`-bound
constant-of-integration parameter. This ignored discrete/continuous
events: a variable a callback impulsively modifies is no longer an
unknown, so a functional (`ImperativeAffect`) kick errors at `ODEProblem`
construction ("... refers to missing variable(s) ... reduced away").
Fix it two ways:
- Auto-detect (default): add `variables_modified_by_events(sys)` in
ModelingToolkitBase and extend `__eliminate_zero_variables!` to protect
event-modified variables using the same seam that already retains
`irreducible` variables. Such a variable stays an ordinary numerically
integrated unknown; unrelated trivial dynamics are still integrated.
- Opt-out flag: `mtkcompile(sys; analytic_integration=false)` disables the
transformation wholesale (threaded to `eliminate_mm_zeros`, composed via
AND so the SDE force-off still wins).
Add a regression testset covering equational and imperative kicks, the
flag, selective protection, and the event-free no-regression case.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
`invalid_variables` (the observed-side check in `compile_functional_affect`) did a naive `setdiff!(search_variables(expr), all_symbols(sys))` with no handling for array symbolics. An array-valued observed handle — e.g. binding an array variable, or a vector of array handles in a reduce-style affect — surfaces as the bare array symbolic `x(t)`, but a flattened system stores it as its scalarized elements `x(t)[i]`, so the bare symbol matched nothing and a valid affect was rejected with "refers to missing variable(s)". Mirror the modified-side `unassignable_variables`: accept the whole-array symbol if present, otherwise walk `stable_eachindex` and check each scalar element. This removes the observed/modified asymmetry — the modified path already accepted array-valued handles. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The array-awareness added to `invalid_variables` checked membership against
`all_symbols(sys)` directly, but that returns a `Vector` — so `var in valid`
used symbolic `==` and errored with "non-boolean used in boolean context"
for every affect with an `observed` clause (scalar or array), breaking even
existing scalar-observed callbacks.
Mirror `unassignable_variables` properly: build a `Set{SymbolicT}` of valid
symbols (scalarizing array symbols into elements) so membership uses
`isequal`/hashing and returns `Bool`, then scalarize array variables on the
lookup side too.
Add a `symbolic_events.jl` testset covering an `ImperativeAffect` whose
`observed` clause reads a whole array-valued variable (builds, solves, and
records the array), plus unit checks that `invalid_variables` accepts a
whole array and a present scalar while still flagging a genuinely missing
variable.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Builds on #4826, but solves a very narrow problem.
invalid_variablesincorrectly flags array variables as invalid, when they are very clearly in the system. Code changes mimicked the array handling inunassignable_variablesChecklist
contributor guidelines, in particular the SciML Style Guide and
COLPRAC.
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