Add support for bundling code that uses import attributes (#3384)
JavaScript is gaining new syntax for associating a map of string key-value pairs with individual ESM imports. The proposal is still a work in progress and is still undergoing significant changes before being finalized. However, the first iteration has already been shipping in Chromium-based browsers for a while, and the second iteration has landed in V8 and is now shipping in node, so it makes sense for esbuild to support it. Here are the two major iterations of this proposal (so far):
Import assertions (deprecated, will not be standardized)
Uses the assert keyword
Does not affect module resolution
Causes an error if the assertion fails
Shipping in Chrome 91+ (and in esbuild 0.11.22+)
Import attributes (currently set to become standardized)
Uses the with keyword
Affects module resolution
Unknown attributes cause an error
Shipping in node 21+
You can already use esbuild to bundle code that uses import assertions (the first iteration). However, this feature is mostly useless for bundlers because import assertions are not allowed to affect module resolution. It's basically only useful as an annotation on external imports, which esbuild will then preserve in the output for use in a browser (which would otherwise refuse to load certain imports).
With this release, esbuild now supports bundling code that uses import attributes (the second iteration). This is much more useful for bundlers because they are allowed to affect module resolution, which means the key-value pairs can be provided to plugins. Here's an example, which uses esbuild's built-in support for the upcoming JSON module standard:
// On static imports
import foo from './package.json' with { type: 'json' }
console.log(foo)
// On dynamic imports
const bar = await import('./package.json', { with: { type: 'json' } })
console.log(bar)
One important consequence of the change in semantics between import assertions and import attributes is that two imports with identical paths but different import attributes are now considered to be different modules. This is because the import attributes are provided to the loader, which might then use those attributes during loading. For example, you could imagine an image loader that produces an image of a different size depending on the import attributes.
Import attributes are now reported in the metafile and are now provided to on-load plugins as a map in the with property. For example, here's an esbuild plugin that turns all imports with a type import attribute equal to 'cheese' into a module that exports the cheese emoji:
Add support for bundling code that uses import attributes (#3384)
JavaScript is gaining new syntax for associating a map of string key-value pairs with individual ESM imports. The proposal is still a work in progress and is still undergoing significant changes before being finalized. However, the first iteration has already been shipping in Chromium-based browsers for a while, and the second iteration has landed in V8 and is now shipping in node, so it makes sense for esbuild to support it. Here are the two major iterations of this proposal (so far):
Import assertions (deprecated, will not be standardized)
Uses the assert keyword
Does not affect module resolution
Causes an error if the assertion fails
Shipping in Chrome 91+ (and in esbuild 0.11.22+)
Import attributes (currently set to become standardized)
Uses the with keyword
Affects module resolution
Unknown attributes cause an error
Shipping in node 21+
You can already use esbuild to bundle code that uses import assertions (the first iteration). However, this feature is mostly useless for bundlers because import assertions are not allowed to affect module resolution. It's basically only useful as an annotation on external imports, which esbuild will then preserve in the output for use in a browser (which would otherwise refuse to load certain imports).
With this release, esbuild now supports bundling code that uses import attributes (the second iteration). This is much more useful for bundlers because they are allowed to affect module resolution, which means the key-value pairs can be provided to plugins. Here's an example, which uses esbuild's built-in support for the upcoming JSON module standard:
// On static imports
import foo from './package.json' with { type: 'json' }
console.log(foo)
// On dynamic imports
const bar = await import('./package.json', { with: { type: 'json' } })
console.log(bar)
One important consequence of the change in semantics between import assertions and import attributes is that two imports with identical paths but different import attributes are now considered to be different modules. This is because the import attributes are provided to the loader, which might then use those attributes during loading. For example, you could imagine an image loader that produces an image of a different size depending on the import attributes.
Import attributes are now reported in the metafile and are now provided to on-load plugins as a map in the with property. For example, here's an esbuild plugin that turns all imports with a type import attribute equal to 'cheese' into a module that exports the cheese emoji:
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Bumps esbuild from 0.19.3 to 0.19.7.
Release notes
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... (truncated)
Changelog
Sourced from esbuild's changelog.
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Commits
a7773b3
publish 0.19.7 to npm2886b5d
more adjustments to import assertions/attributes2dad830
add basic support for import assertions6b9737a
fix test262 crash in v8 due to renamed test0d9f765
fix #3230, fix #3326, fix #3394: update decorators9fc1ed3
ast helpers: use a context object00fa010
tree shaking: handle destructuring of an arrayf361c7f
fix #3477: forbid--keep-names
if not supported4c64c19
compat-table: sort kangax feature mapcd7b93f
dev server: add a fallbackfavicon.ico
handlerDependabot 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 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