fix(compat): don't bind function from globalProperties to the current istance if it has additional properties

[LinusBorg]

Problem

In Vue 2, we add global properties to the Vue prototype:

Vue.prototype.$myFunc = function ) { /* ... */}

This will automatically make this in such a function point ot the component instance.

In Vue 3's compat behaviour, we need to call fn.bind(proxy) to achieve a similar behaviour.

But this poses a problem for funtions that 1) don't need access to the component proxy and 2) have additional properties, which are lost during fn.bind():

app.config.globalProperties.$axios = axios

// 

this.$axios.post() // => post is undefined

Solution

To accomodate fort his common usecase, I added a check for Object.keys(val).length === 0. The reasoning being: if the function has additional properties, it is almost surely an external library and not a plain function meant to be used as an instance method.

Alternatives

We could alternatively re-apply all of the custom properties that we found with Object.keys() onto the new bound function. But I'm not convinced the effort and additional code would be worth the gains.

close #4403

[LinusBorg]

I'm can't follow ...

[caozhong1996]

Sorry for my broken English, I misunderstood something yesterday.

We could alternatively re-apply all of the custom properties that we found with Object.keys() onto the new bound function. But I'm not convinced the effort and additional code would be worth the gains.

Why not do so? Or perhaps we could simply use Object.assign(). I am quite curious, would you like to talk about the details? Thanks.

[yyx990803]

I also think copying any existing self properties would be safer - the assumption that "a function with extra properties doesn't need access to this" seems pretty fragile to me.

Copying with Object.assign should be acceptable since in most cases the function will have no extra properties, and the code path only affects the compat build.

[LinusBorg]

Agreed, will make the necessary change

[LinusBorg]

No idea why the PR test runs fail, and the push ones run fine ... 🧐

[caozhong1996]

It seems caused by #4807🤔

[yyx990803]

Yeah, it's been reverted in latest master - @LinusBorg can you rebase and add a test case?

[LinusBorg]

Done

[raind33]

Done

published? which version?