Support JSON.parse() with a string in the CSP evaluator - #4913
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Server-side helpers emit JSON.parse('…') for arrays and objects; Laravel's
@js() and Js::from() do it for every non-scalar value. The CSP evaluator
resolved JSON like any other global, so those expressions failed with
"Undefined variable: JSON" and every array reaching an Alpine attribute
through such a helper broke under the CSP build.
Parsing JSON runs no code, so the evaluator now treats JSON.parse() with a
single string argument as an intrinsic: the argument is evaluated, must be
a string, and is parsed with the native JSON.parse(). The JSON global
itself stays unreachable (JSON.stringify(), JSON['parse'], a bare JSON
all still throw), a JSON defined in scope still takes precedence, and
each evaluation returns a fresh value, as native code would.
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Server-side helpers emit
JSON.parse('…')for arrays and objects; Laravel's@js()andJs::from()do it for every non-scalar value. The CSP evaluator resolvesJSONlike any other global, so every one of those expressions fails withUndefined variable: JSON, and any array that reaches an Alpine attribute through such a helper breaks under the CSP build.Why now. Livewire's
csp_safemode uses this build, and Filament is working on supporting it: a scan of Filament's templates found 57@js()arrays inside Alpine attributes, the largest single category of what breaks. Dan Harrin asked for this to be solved here rather than with a Filament-specific replacement for@js(): filamentphp/filament#7032 (reply in thread)What this does.
JSON.parse()with a single string argument becomes an intrinsic of the evaluator. Parsing JSON runs no code, so it does not weaken the sandbox. The rest of theJSONglobal stays unreachable:JSON.stringify(), a bareJSON, andJSON['parse']all still throw. AJSONdefined in scope takes precedence, the argument may come from scope as well as from a literal, and each evaluation returns a fresh value, as native code would.Unit tests for all of the above, a Cypress test with the exact output
Js::from()produces (including its"escapes), and a docs entry.