fix: don't generate title tag if title is empty

[clarkdo]

Fix nuxt/nuxt#5281

[codecov-io]

Codecov Report

Merging #334 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #334   +/-   ##
=======================================
  Coverage   40.89%   40.89%           
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  Files          19       19           
  Lines         269      269           
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  Hits          110      110           
  Misses        159      159

Impacted Files	Coverage Δ
src/server/generators/titleGenerator.js	0% <0%> (ø)	⬆️

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[TheAlexLichter]

I wouldn't think of this behavior normally (when using vue-meta in context of a typical SPA and not going for microfrontends or similar). Please add at least a comment there ☺️

Also, maybe checking for undefined instead of using all falsy values might make sense? 🤔

[clarkdo]

I changed the checking to String(data) for keeping it same behaviour as document.title=....

document.title = undefined // <title>undefined</title>
document.title = null // <title>null</title>
document.title = false // <title>false</title>
document.title = 0 // <title>0</title>
document.title = '' // <title> tag will be removed

[TheAlexLichter]

It makes sense to be in line with document.title here but I'm not sure if being in line with the vue-meta-own conventions might be more important (though that will only be relevant for v2)

[TheAlexLichter]

If that PR gets merged, we have to port it to the nextranch too ☺️

[pimlie]

I am ok with this as html5 spec says the title element is required unless its reasonable not to. Also chrome/firefox behave the same when title doesnt exists as when its an empty string.

Even though you could also argue this issue should be fixed in Nuxt, because vue-meta already provides the option to ignore the title on ssr by simply not calling {{ $meta.title.text() }} in your template.

[clarkdo]

@pimlie I fixed this issue in vue-meta since nuxt needs to resolve global and component head title config for checking if meta.title should be called which may bring unnecessary code and overhead.

[pimlie]

@clarkdo the other options would be to either pass an argument to text() to make the behaviour optional (less favourable) or add a global config option so users can indicate that a vue-meta property should be ignored (regardless whether it has a value or not).

Strictly speaking (as in according to the spec) the title element could not only be not printed on empty string but also when it only contains inter-element white space. So String(data).trim() would maybe be more in-line with the spec. The end result in the browser will be exactly the same though as the browser will ignore a title containing only spaces/line-breaks anyways.

[atinux]

Ready to merge for minor, I let you handle it @pimlie when you feel ready for it :)