check-types: Traversing variadic AST (for function(...)) gives "TypeError: Cannot read property 'type' of null"

[vapier]

code snippet:

/** @param {function(...)} callback The function to invoke. */
var subscribe = function(callback) {};

eslint crashes:

TypeError: Cannot read property 'type' of null
Occurred while linting test.js:2
    at .../node_modules/eslint-plugin-jsdoc/dist/rules/checkTypes.js:133:25
    at opt_onEnter (.../node_modules/jsdoctypeparser/lib/traversing.js:19:7)
...

this basically means the func accepts an arbitrary number of arguments of arbitrary type.

• eslint-6.4.0
• eslint-15.9.5
• jsdoctypeparser-5.0.1

[brettz9]

This appears, in a sense, to be an issue with jsdoctypeparser. While we could wrap the call to the traverse function in a try-catch, jsdoctypeparser shouldn't be passing the parsing stage and failing at the traverse stage.

So an issue should really be filed there.

However, I'm not sure what the course of action should be in this case. It is not entirely clear that the variadic format you are using--three dots not followed by anything--is considered acceptable or not (and if so by which jsdoc dialects).

• Closure does not make explicit mention of such a type: https://github.com/google/closure-compiler/wiki/Annotating-JavaScript-for-the-Closure-Compiler ; though the jsdoctypeparser pegjs source points to a file using this format at this line?), I'm not sure that this single example is authoritative.
• I'm not sure about TypeScript; seems there is an issue filed to add support for variadic in general--not sure about the empty format: Proposal: Variadic Kinds -- Give specific types to variadic functions microsoft/TypeScript#5453
• vanilla jsdoc, whether at https://jsdoc.app/tags-type.html or https://jsdoc.app/tags-param.html do not make mention of such a type.
• JSDuck does not seem to support: https://github.com/senchalabs/jsduck/wiki/Type-Definitions

As a workaround (until determination is made on whether to eliminate this possibility or fully support it) you might use ...* or ...any.

[brettz9]

This is now blocking on jsdoctypeparser/jsdoctypeparser#89 .

Feel free to subscribe there.

[gajus]

🎉 This issue has been resolved in version 15.9.9 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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