Add documentation requirements for @template descriptions, similar to @param

[spaceribs]

Motivation

To better support and require generic type descriptions via @template

Current behavior

No rules require @template to be defined, or require a description if it is defined.

Desired behavior

The following rules are created/added:

"jsdoc/require-template"
"jsdoc/require-template-description"
"jsdoc/require-template-name"

This rule should detect if a generic is added to a function, class, type alias or interface and perform
the same functionality as jsdoc/require-param

Alternatives considered

None, could not find this functionality, only similar patterns

[brettz9]

You can get the require-template-name behavior with the jsdoc/match-name rule as follows:

        {
          match: [
            {
              disallowName: '/^$/',
              tags: [
                'template',
              ],
            },
          ],
        },

For require-template-description, see match-description with the tags option.

For require-template, I am having trouble seeing why you would want to add it to every function, etc.

You could use jsdoc/no-restricted-syntax though it wouldn't auto-add a missing @template (it would just report that one was missing); you'd need to add further to the context as desired:

        {
          contexts: [
            {
              comment: 'JsdocBlock:not(*:has(JsdocTag[tag=template]))',
              context: 'ArrowFunctionExpression,FunctionDeclaration,FunctionExpression,TSDeclareFunction',
              message: '@template required on each block',
            },
          ],
        },

[spaceribs]

that certainly works in the meantime, but I'd assume type parameters are just as important to document as parameters? why wouldn't we want to make it a more straightforward process for requiring an explanation as to what is expected to be passed in?

[brettz9]

Can you give me a precise example of code where you'd like to see @template required?

[spaceribs]

@brettz9 sure, here's an example I'm working with:

/**
 * A tuple of the coordinates and the value at the coordinate.
 */
export type Pairs<D, V> = [D, V | undefined];

/**
 * For a particular axis, a tuple representing the element before
 * and after
 */
export type BeforeAfter<D, V> = [Pairs<D, V>, Pairs<D, V>];

[brettz9]

Ok, I see, so you are using TypeScript syntax rather than using JavaScript with a TypeScript flavor and you want to enforce @template only when generics are used in the signature.

So I see a need for require-template as a rule, though I think require-template-name and require-template-description can be met by match-name and match-description rather than proliferating the rules here.

We might be able to add our nameRequired internal metadata to the @template tag, however, causing our valid-types rule to report any missing names for @template since I expect we can effectively require it with this tag.

[spaceribs]

makes sense, I requested the others because it seems to match the established pattern, no problems nixing that.

[brettz9]

We probably could use, however, a separate rule (in addition to the require-param equivalent) corresponding to check-param-names--i.e., check that if @templates are supplied, that they exist on the type. I.e., add a require-template and check-template-names.

[brettz9]

And we might not just check TypeScript proper, but check any @typedef which used template values (and have a rule to check that any template values are present in the typedef if one is present on the block).

Also, in the require-template case, I think we might want an option to require that each template has a separate @template so it can be independently described (rather than using the @template T,U,V syntax).

[brettz9]

I've added a PR to provide some support, but so far, only for the type alias structures (at root or exported) which you indicated. Maybe we can just release it now and gradually build support for other structures, as I'm sure there are many that could be supported.

[brettz9]

Please feel free to enable the rule and try it out... jsdoc/require-template. See https://github.com/gajus/eslint-plugin-jsdoc/blob/main/docs/rules/require-template.md#readme