The "preserve" JSX mode now preserves JSX text verbatim (#3605)
The JSX specification deliberately doesn't specify how JSX text is supposed to be interpreted and there is no canonical way to interpret JSX text. Two most popular interpretations are Babel and TypeScript. Yes they are different (esbuild deliberately follows TypeScript by the way).
Previously esbuild normalized text to the TypeScript interpretation when the "preserve" JSX mode is active. However, "preserve" should arguably reproduce the original JSX text verbatim so that whatever JSX transform runs after esbuild is free to interpret it however it wants. So with this release, esbuild will now pass JSX text through unmodified:
// Original code
let el =
<a href={'/'} title=''"'> some text
{foo}
more text </a>
// Old output (with --loader=jsx --jsx=preserve)
let el = <a href="/" title={'"}>
{" some text"}
{foo}
{"more text "}
</a>;
// New output (with --loader=jsx --jsx=preserve)
let el = <a href={"/"} title=''"'> some text
{foo}
more text </a>;
Allow JSX elements as JSX attribute values
JSX has an obscure feature where you can use JSX elements in attribute position without surrounding them with {...}. It looks like this:
let el = <div data-ab=<><a/><b/></>/>;
I think I originally didn't implement it even though it's part of the JSX specification because it previously didn't work in TypeScript (and potentially also in Babel?). However, support for it was silently added in TypeScript 4.8 without me noticing and Babel has also since fixed their bugs regarding this feature. So I'm adding it to esbuild too now that I know it's widely supported.
Keep in mind that there is some ongoing discussion about removing this feature from JSX. I agree that the syntax seems out of place (it does away with the elegance of "JSX is basically just XML with {...} escapes" for something arguably harder to read, which doesn't seem like a good trade-off), but it's in the specification and TypeScript and Babel both implement it so I'm going to have esbuild implement it too. However, I reserve the right to remove it from esbuild if it's ever removed from the specification in the future. So use it with caution.
This release fixes a bug with esbuild's TypeScript parser where a conditional type containing a union type that ends with an infer type that ends with a constraint could fail to parse. This was caused by the "don't parse a conditional type" flag not getting passed through the union type parser. Here's an example of valid TypeScript code that previously failed to parse correctly:
type InferUnion<T> = T extends { a: infer U extends number } | infer U extends number ? U : never
The "preserve" JSX mode now preserves JSX text verbatim (#3605)
The JSX specification deliberately doesn't specify how JSX text is supposed to be interpreted and there is no canonical way to interpret JSX text. Two most popular interpretations are Babel and TypeScript. Yes they are different (esbuild deliberately follows TypeScript by the way).
Previously esbuild normalized text to the TypeScript interpretation when the "preserve" JSX mode is active. However, "preserve" should arguably reproduce the original JSX text verbatim so that whatever JSX transform runs after esbuild is free to interpret it however it wants. So with this release, esbuild will now pass JSX text through unmodified:
// Original code
let el =
<a href={'/'} title=''"'> some text
{foo}
more text </a>
// Old output (with --loader=jsx --jsx=preserve)
let el = <a href="/" title={'"}>
{" some text"}
{foo}
{"more text "}
</a>;
// New output (with --loader=jsx --jsx=preserve)
let el = <a href={"/"} title=''"'> some text
{foo}
more text </a>;
Allow JSX elements as JSX attribute values
JSX has an obscure feature where you can use JSX elements in attribute position without surrounding them with {...}. It looks like this:
let el = <div data-ab=<><a/><b/></>/>;
I think I originally didn't implement it even though it's part of the JSX specification because it previously didn't work in TypeScript (and potentially also in Babel?). However, support for it was silently added in TypeScript 4.8 without me noticing and Babel has also since fixed their bugs regarding this feature. So I'm adding it to esbuild too now that I know it's widely supported.
Keep in mind that there is some ongoing discussion about removing this feature from JSX. I agree that the syntax seems out of place (it does away with the elegance of "JSX is basically just XML with {...} escapes" for something arguably harder to read, which doesn't seem like a good trade-off), but it's in the specification and TypeScript and Babel both implement it so I'm going to have esbuild implement it too. However, I reserve the right to remove it from esbuild if it's ever removed from the specification in the future. So use it with caution.
This release fixes a bug with esbuild's TypeScript parser where a conditional type containing a union type that ends with an infer type that ends with a constraint could fail to parse. This was caused by the "don't parse a conditional type" flag not getting passed through the union type parser. Here's an example of valid TypeScript code that previously failed to parse correctly:
type InferUnion<T> = T extends { a: infer U extends number } | infer U extends number ? U : never
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Bumps esbuild from 0.19.11 to 0.19.12.
Release notes
Sourced from esbuild's releases.
Changelog
Sourced from esbuild's changelog.
Commits
d7fd1ad
publish 0.19.12 to npme04a690
fix #3605: print the original JSX AST unmodifiedf571399
allow jsx elements as jsx attribute valuesa652e73
runmake update-compat-table
35c0d65
fix #3574: ts type parser bug with infer + extendsf6eae0c
fix #3569: incorrect ToInt32 behavior on riscv64Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting
@dependabot rebase
.Dependabot will merge this PR once CI passes on it, as requested by @asaaki-bot.
Dependabot commands and options
You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot merge` will merge this PR after your CI passes on it - `@dependabot squash and merge` will squash and merge this PR after your CI passes on it - `@dependabot cancel merge` will cancel a previously requested merge and block automerging - `@dependabot reopen` will reopen this PR if it is closed - `@dependabot close` will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually - `@dependabot show