noUnsafeOptionalChaining (since v12.0.0)
Disallow the use of optional chaining in contexts where the undefined value is not allowed.
The optional chaining (?.) expression can short-circuit with a return value of undefined. Therefore, treating an evaluated optional chaining expression as a function, object, number, etc., can cause TypeError or unexpected results. Also, parentheses limit the scope of short-circuiting in chains.
Examples
Invalid
1 in obj?.foo;nursery/noUnsafeOptionalChaining.js:1:9 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ 1 in obj?.foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ 1 in obj?.foo;
│ ^^^^^^^^^^^^^
2 │
with (obj?.foo);nursery/noUnsafeOptionalChaining.js:1:10 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ with (obj?.foo);
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ with (obj?.foo);
│ ^^^^^^^^^^^^^^^^
2 │
for (bar of obj?.foo);nursery/noUnsafeOptionalChaining.js:1:16 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ for (bar of obj?.foo);
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ for (bar of obj?.foo);
│ ^^^^^^^^^^^^^^^^^^^^^^
2 │
bar instanceof obj?.foo;nursery/noUnsafeOptionalChaining.js:1:19 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ bar instanceof obj?.foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ bar instanceof obj?.foo;
│ ^^^^^^^^^^^^^^^^^^^^^^^
2 │
const { bar } = obj?.foo;nursery/noUnsafeOptionalChaining.js:1:20 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ const { bar } = obj?.foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ const { bar } = obj?.foo;
│ ^^^^^^^^^^^^^^^^^^
2 │
(obj?.foo)();nursery/noUnsafeOptionalChaining.js:1:5 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ (obj?.foo)();
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ (obj?.foo)();
│ ^^
2 │
(baz?.bar).foo;nursery/noUnsafeOptionalChaining.js:1:5 lint/nursery/noUnsafeOptionalChaining ━━━━━━━━━━━━━━━━━━━━━━
✖ Unsafe usage of optional chaining.
> 1 │ (baz?.bar).foo;
│ ^^
2 │
ℹ If it short-circuits with 'undefined' the evaluation will throw TypeError here:
> 1 │ (baz?.bar).foo;
│ ^^^
2 │
Valid
(obj?.foo)?.();
obj?.foo();
(obj?.foo ?? bar)();
obj?.foo.bar;
obj.foo?.bar;
foo?.()?.bar;