fix(template): only auto-call callables that take zero arguments - #56
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The nightly `template_parse_render` fuzz target aborted on `<%= patch%>`:
panicked at src/interpreter/builtins/request_helpers.rs:73:
index out of bounds: the len is 0 but the index is 0
Omitting parentheses is documented as a zero-argument form (`<%= now.to_iso
%>`), but the renderer auto-called *every* callable it evaluated, passing an
empty argument list. So naming a helper that needs arguments ran its body with
nothing in it. The request helpers are registered variadic — `arity: None`
means "the runtime does not check the count", not "takes no arguments" — so
`patch` read `args[0]` on an empty slice. A panic aborts without unwinding, out
of reach of the per-request `catch_unwind`.
Two fixes, at the choke point and at the destination:
- `auto_call_if_callable` now invokes only callables that genuinely accept zero
arguments, using the same predicate as a bare name in code
(`can_auto_invoke_with_no_args`, which `try_auto_invoke` also calls now so
the two surfaces cannot drift). A callable that needs arguments renders as
its value instead of being called. This closes the whole class from the
template surface, not just `patch`.
- The request helpers bounds-check their arguments (`arg_string`), so calling
one directly with too few raises "… is missing a required argument" rather
than panicking.
The minimized reproducer is a tracked fuzz seed. Regression tests cover both
directions: a helper needing arguments does not panic, and a genuine zero-arg
method is still called without parentheses.
Note: ~760 other builtins still index `args[N]` unchecked, reachable by calling
one with too few arguments from Soli code. Not touched here.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
…t 241 Two things that made the fuzz job red for reasons unrelated to the code under test. LeakSanitizer. cargo-fuzz builds with AddressSanitizer, which enables LSan too, and nothing set ASAN_OPTIONS. These targets exist to catch panics, stack overflows and UB in the surfaces that take untrusted input — not to audit allocation lifetimes. The interpreter is `Rc<RefCell<…>>`-based, so a closure capturing its defining environment forms a reference cycle that LSan correctly calls an unreachable "direct leak"; it is bounded and harmless in a process that exits. On PR #55 that failed the job *after* a completely clean fuzz — `Done 72817 runs in 21 second(s)`, then 446 bytes in 36 allocations — so every PR touching a fuzzed path inherited a red X that had nothing to do with its diff. Leak detection is now off for the fuzz step. The backtick guard in `template_parse_render` predates this and was partly justified by the same LSan behaviour; its other reason — rendering a backtick tag runs `sh -c <fuzzer bytes>` on the host — stands on its own, so the guard stays and the comment now says why. Unwrap ratchet. The regression tests added in the previous commit pushed `src/template` from 241 to 244 `.unwrap()`/`.expect()` calls and failed `scripts/lint_unwraps.sh`. The ratchet is meant to move in one direction, so the tests were rewritten to not need them (`let Ok(…) else`, and comparing against `Ok("ADA".to_string())`) rather than raising the baseline. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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The nightly
template_parse_renderfuzz target aborted on<%= patch%>:Omitting parentheses is documented as a zero-argument form (
<%= now.to_iso %>), but the renderer auto-called every callable it evaluated, passing an empty argument list. So naming a helper that needs arguments ran its body with nothing in it. The request helpers are registered variadic —arity: Nonemeans "the runtime does not check the count", not "takes no arguments" — sopatchreadargs[0]on an empty slice. A panic aborts without unwinding, out of reach of the per-requestcatch_unwind.Two fixes, at the choke point and at the destination:
auto_call_if_callablenow invokes only callables that genuinely accept zero arguments, using the same predicate as a bare name in code (can_auto_invoke_with_no_args, whichtry_auto_invokealso calls now so the two surfaces cannot drift). A callable that needs arguments renders as its value instead of being called. This closes the whole class from the template surface, not justpatch.arg_string), so calling one directly with too few raises "… is missing a required argument" rather than panicking.The minimized reproducer is a tracked fuzz seed. Regression tests cover both directions: a helper needing arguments does not panic, and a genuine zero-arg method is still called without parentheses.
Note: ~760 other builtins still index
args[N]unchecked, reachable by calling one with too few arguments from Soli code. Not touched here.