Proposal: no bare strings in template

[patric-eberle]

Please describe what the rule should do:
Projects which use localization (e.g. vue-i18n) should not allow the use of bare strings (hardcoded strings) in templates. They should force the use the mustache syntax or directives.

This proposal is based on the Ember template linter, which includes such a rule already: https://github.com/ember-template-lint/ember-template-lint/blob/master/docs/rule/no-bare-strings.md

What category of rule is this? (place an "X" next to just one item)

[x] Enforces code style
[ ] Warns about a potential error
[ ] Suggests an alternate way of doing something
[ ] Other (please specify:)

Provide 2-3 code examples that this rule will warn about:
Invalid template content

<h1>Foo baa</h1>

Valid template content

<h1>{{ $t('myTranslationKey') }}</h1>
<h1>{{ aComputedValue }}</h1>
<h1 v-t="'foo.bar'"></h1>
<h1><span>{{ aComputedValue }}</span></h1>

Why should this rule be included?
It allows to test templates for hardcoded text which most likely will lead to issues in localized projects.

[michalsnik]

I like this idea! I always used this rule in Ember projects 👍

[chrisvfritz]

This is indeed a good rule for localization! Since it wouldn't apply to many projects though, I think it would be uncategorized. One question though: should the following be valid?

<h1 v-t="'foo.bar'"></h1>

Or should it instead be:

<h1 v-t="foo.bar"></h1>

?

[patric-eberle]

@chrisvfritz I would recommend to not check this with eslint because both usages are valid. I think for what you want to do the first one would be correct. See https://kazupon.github.io/vue-i18n/api/#directives - Still the second example with no single quotes would also be valid if you want to bind an instance property.

[chrisvfritz]

Ah, I see. Then we may want to disable string literals for directives, with a whitelist of some directives, like v-t and the user could add their own as well. Otherwise, we open up a big hole with v-text, v-html, and directives defined by other libraries, like v-tooltip. For example:

<p v-text="'hello'"/>

<button v-tooltip="'Hard-coded button tooltip content'">

We probably don't want those to be considered valid, right?

[patric-eberle]

Ah, I see what you mean. I think your recommondation makes sense.

[michalsnik]

Also depending on element the white-list might look a bit different.

Let's take <input> tag as example.

<input type="text" :class="classObj" value="1" style="width: 100%" disabled="disabled">

Above HTML probably shouldn't trigger any error. But setting value attribute on other component might.

The most straightforward cases are at this moment:

<div>plain text</div>
<div>{{ 'another plain text' }}</div>

I'll try to come up with an idea how to handle the rest of the cases to not introduce unnecessary false-positives.

[michalsnik]

I gave it a second thought and I like how it is solved in ember-template-lint. I used their rule in all of my commercial Ember projects and it actually worked really well. I don't think we should go crazy here, and perhaps similar approach would suffice.

The following cases might be considered warnings then:

1. Plain text, excluding signs like: (),.&+-=*/#%!?:[]{}.

<div>text</div>

2. Global attributes on only-HTML elements:
   By default these attributes: title, aria-label, aria-placeholder, aria-roledescription, aria-valuetext

<div
  title="text"
  aria-label="label"
  aria-placeholder="placeholder"
  aria-roledescription="desc"
  aria-valuetext="text"
/>

3. Tag specific attributes:
   By default: { img: ['alt'], input: ['placeholder'] }

<img alt="text">
<input placeholder="text">

4. Certain directives
   By default: ['v-text', 'v-html']

<div v-text="'lorem ipsum'" />
<div v-html="'lorem ipsum'" />

Users could add more attributes or directives to make this rule more rigid if they want.

Also I'm not sure if we should report a warning when user explicitly returns a string in an expression:

{{ 'text' }}

This looks like a conscious decision to me, similar to bindings:

<a :title="'lorem ipsum" />

What do you think @chrisvfritz @patric-eberle ?

[patric-eberle]

@michalsnik I think keeping it simple should be ok. I think the rule makes most sense for content and static text attributes. I also think it‘s not necessary to test bindings and expressions.

[chrisvfritz]

Sounds good to me. 🙂