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Type annotation is stripped from Typescript template #10636

dentrado opened this issue Nov 4, 2019 · 2 comments


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@dentrado dentrado commented Nov 4, 2019

Bug Report

Current Behavior
A @babel/template template with placeholders and a type annotation generates code without the annotation. A template without placeholders works as expected.

Input Code

const template = require('@babel/template').default
const generate = require('@babel/generator').default
const t = require('@babel/types')
const withType = template({plugins:['typescript']}).ast`
    const greeting: string = 'Hello';
// => "const greeting: string = 'Hello';"const typeDisappears = template({plugins:['typescript']}).ast`
    const ${t.identifier('greeting')}: string = 'Hello';
// => "const greeting = 'Hello';"

Expected behavior/code

I expect both templates above to keep the : string type in the generated code.

Babel Configuration (.babelrc, package.json, cli command)

No configuration, used from code, see above.


  • Babel version(s): 7.6.4
  • Node/npm version: Node 12.9.1 / yarn 1.17.3
  • Monorepo: no

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@babel-bot babel-bot commented Nov 4, 2019

Hey @dentrado! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."


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@nicolo-ribaudo nicolo-ribaudo commented Nov 4, 2019

The root cause of this bug is that the type annotation is a child node of the identifier. The identifier you are passing to @babel/template doesn't have the type annotation, and thus the one in the template is discarded.

#9545 would be a possible way of fixing this.

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