The `map`, `join`, and `contains` expression filters assumed their
argument was a string. A non-string argument — an authoring mistake such
as `| map(5)`, `| join(5)`, or `| contains(5)` — reached an operation
that only strings support and raised a cryptic exception that escaped the
evaluator entirely:
* `map(5)` -> `attr.split(".")` -> AttributeError
* `join(5)` -> `separator.join(...)` -> AttributeError
* `contains(5)` on a string value -> `x in str` -> TypeError
The engine wraps neither expression evaluation nor `step_impl.execute()`
in a try/except, so each of these took down the whole run with a message
that names none of the real problem.
Validate the argument type up front and raise a `ValueError` naming the
filter and the offending type instead, mirroring the strict argument
handling already in `from_json`. `contains` guards only the string-value
branch: for a list value, membership of any element type is legitimate
(`5 in [1, 2, 5]`), so that branch is intentionally left unguarded.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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