Changing compilerOptions directives in vue.config.js not working in 2.7 when building

[tunnelpuzzle]

Version

2.7.12

Reproduction link

github.com

Steps to reproduce

1. Clone the minimal reproduction repo and do npm run build. The code in vue.config.js: https://github.com/tunnelpuzzle/vue-compiler-directive/blob/master/vue.config.js#L11-L12 for the v-show directive won't be run.

2. Switch to Vue 2.6 npm i vue@2.6.14 vue-template-compiler@2.6.14 and then do npm run build. The code to for the v-show directive is run.

What is expected?

Changing the compilerOptions directives should work in Vue 2.7 when building.

What is actually happening?

Changing the compilerOptions directives when building works in Vue 2.6 but not Vue 2.7

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I looked in the release notes but couldn't find anything about this behavior changing in 2.7.

[yyx990803]

/cc @sodatea this seems to be related to thread-loader not able to pass options that contain functions to worker thread (only in build).

Not sure why this behavior is different between 2.6 and 2.7. Is there some logic in vue-cli that enables/disables thread-loader on vue-loader?

For now you can work around this by setting parallel: false in vue.config.js.

[haoqunjiang]

Not sure why this behavior is different between 2.6 and 2.7. Is there some logic in vue-cli that enables/disables thread-loader on vue-loader?

It's in vue-loader.
Vue 2.7+ also applies js loaders to compiled <template> code, and among them is thread-loader.
Vue 2.6 template compilation doesn't go through js loaders, thus no problem.

[haoqunjiang]

This issue could be mostly mitigated if we detect and skip cloning thread-loader rules in VueLoaderPlugin

[haoqunjiang]

Fixed in vue-loader@15.10.1