Add "ignoreUninitialized" option to "@babel/proposal-class-properties"#9141
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nicolo-ribaudo wants to merge 1 commit intobabel:masterfrom
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Add "ignoreUninitialized" option to "@babel/proposal-class-properties"#9141nicolo-ribaudo wants to merge 1 commit intobabel:masterfrom
nicolo-ribaudo wants to merge 1 commit intobabel:masterfrom
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When this option is set to true, Babel ignores public class fields
without an initializer. e.g. This code:
class A { x; }
becomes
class A {}
This behavior, althought it diverges from the class fields proposal and
thus isn't reccomended, matches Flow and TypeScript's behavior.
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Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/9606/ |
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Is this going to be merged? Whether or not typescript changes their uninitialized field behavior, it will take quite some time for libraries to be updated for the breaking change. So to make @babel/typescript feasible today there needs to be a way to match tsc. |
This was referenced May 14, 2019
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Author
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I'm closing this plugin since we are not going to diverge from the spec on pourpouse. |
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This PR introduces a new option to the
@babel/plugin-proposal-class-propertiesplugin:ignoreUninitialized. When it is enabled,foo;andfoo: type;are removed instead of being (correctly) transpiled as if they werefoo = undefined;.This is needed to support the non-standard behavior of Flow and TypeScript, which use uninitialized fields as build-time-only type annotations instead of undefined fields (as mandated by the proposal). This bug has already been reported to those projects (microsoft/TypeScript#12437, facebook/flow#6811).
When documenting this option we must add a warning that if you are using this option, your code will be incompatible with fields natively implemented by JS engines. We should propose this as an option to make the Flow/TypeScript -> Babel migration easer, but we should encurage users to refactor their code to follow the current proposal.
cc @babel/typescript @babel/flow