☂️ Transpiler / Transformer

[Boshen]

Contribution Instructions

The implementation is in crates/oxc_transformer.

To get started, take a look at the previous implementations.

The integrations tests are located in tasks/transform_conformance/src/lib.rs,
Run it with just watch 'run -p oxc_transform_conformance' or with a filter just watch "run -p oxc_transform_conformance -- --filter type-arguments".

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Tasks

• chore(transformer): add comprehensive benchmark #979
• feat(transformer): add unit tests and test coverage #1001
• feat(transformer): run exec.js from babel tests #999
• Fix transformer benchmark because it is transforming the already transformed AST fix(benchmark): bench the whole transformation pipeline #998

Third Party Plugins

• https://www.npmjs.com/package/babel-plugin-import

Feature list

Legend:

• [Syntax] means this is a syntax plugin, no code is required because it is supported by the parser.
• [Regex] means this is a regex transform, which is not supported.
• [Codegen] means the code generator is responsible for the feature.

@babel/preset-react

• @babel/plugin-transform-react-jsx

@babel/preset-typescript

• @babel/plugin-transform-typescript

@babel/preset-env

ES2024

• [Regex] unicode-sets-regex

ES2023

Does not have any features.

ES2022

• class-properties
• class-static-block feat(transformer): Class Static Block #962
• private-methods
• private-property-in-object
• [Syntax] syntax-top-level-await

ES2021

• logical-assignment-operators feat(transformer): logical assignment operators #923
• [Syntax] numeric-separator

ES2020

• dynamic-import
• export-namespace-from
• nullish-coalescing-operator feat(transformer): ES2020 Nullish Coalescing Operator #1004
• optional-chaining
• [Syntax] syntax-bigint
• [Syntax] syntax-dynamic-import
• [Syntax] syntax-import-meta

ES2019

• optional-catch-binding
• [Codegen] json-strings

ES2018

• async-generator-functions
• object-rest-spread
• [Regex] unicode-property-regex
• [Regex] dotall-regex
• [Regex] named-capturing-groups-regex

ES2017

• async-to-generator

ES2016

• exponentiation-operator feat(transformer): finish 2016 exponentiation operator #996

ES2015

• arrow-functions
• block-scoping
• classes
• computed-properties
• destructuring
• duplicate-keys
• for-of
• function-name
• instanceof
• literals
• new-target
• object-super
• parameters
• shorthand-properties feat(transformer): Shorthand Properties #960
• spread
• sticky-regex feat(transform): sticky-regex #968
• template-literals
• typeof-symbol
• [Regex] unicode-escapes
• [Regex] unicode-regex

[Boshen]

I'm going to start with https://github.com/babel/babel/blob/main/packages/babel-plugin-transform-nullish-coalescing-operator/src/index.ts, which is simple but requires adding new variables to the scope.

[rzvxa]

@Boshen Is there any reason why some of these parts aren't checked while having an implementation in the transformer? If it is simply outdated let me know to take over it and keep it in sync with our progress.

[Boshen]

Closing in favor of the redo in #2859