warn if $set is used on a property that already exist · vuejs/vue#8129

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feature requestgood first issuehas PR

描述

2.5.16

See the codepen snippet. Follow the comment there to change the vm's data and see what happens.

Even if the prop already exists, using set still makes it reactive, thus trigger view update.

Using set later doesn't update the view.

Related source code: https://github.com/vuejs/vue/blob/3eb37acf98e2d9737de897ebe7bdb7e9576bcc21/src/core/observer/index.js#L192 I think most users would expect set to make the prop reactive whenever it's used. I initially opened an issue for the api doc because it wasn't clear (for me) about this. But the comment in the source code is.

技術棧: javascriptvue
領域: frontend
議題類型: bug
難度: 3
預計時間: 1-3 hours
活動狀態: stale
清晰度: mostly clear
前置要求: JavaScriptVue.js reactivityObserver pattern
新手友善度: 70
研究方向: Investigate the source code at src/core/observer/index.js, specifically the `set` function. The issue mentions that if a property already exists, Vue.set does not trigger reactivity. Look at how the observer handles setting properties. The expected behavior is that Vue.set should always make a property reactive, even if it already exists. Suggest adding a check to ensure that if the property already exists, it still calls `defineReactive` to make it reactive. Additionally, consider the implications for nested objects and arrays.