v0.18.0
This release deliberately contains backwards-incompatible changes. To avoid automatically picking up releases like this, you should either be pinning the exact version of esbuild
in your package.json
file (recommended) or be using a version range syntax that only accepts patch upgrades such as ^0.17.0
or ~0.17.0
. See npm's documentation about semver for more information.
The breaking changes in this release mainly focus on fixing some long-standing issues with esbuild's handling of tsconfig.json
files. Here are all the changes in this release, in detail:
-
Add a way to try esbuild online (#797)
There is now a way to try esbuild live on esbuild's website without installing it: https://esbuild.github.io/try/. In addition to being able to more easily evaluate esbuild, this should also make it more efficient to generate esbuild bug reports. For example, you can use it to compare the behavior of different versions of esbuild on the same input. The state of the page is stored in the URL for easy sharing. Many thanks to @hyrious for creating https://hyrious.me/esbuild-repl/, which was the main inspiration for this addition to esbuild's website.
Two forms of build options are supported: either CLI-style (example) or JS-style (example). Both are converted into a JS object that's passed to esbuild's WebAssembly API. The CLI-style argument parser is a custom one that simulates shell quoting rules, and the JS-style argument parser is also custom and parses a superset of JSON (basically JSON5 + regular expressions). So argument parsing is an approximate simulation of what happens for real but hopefully it should be close enough.
-
Changes to esbuild's
tsconfig.json
support (#3019):This release makes the following changes to esbuild's
tsconfig.json
support:-
Using experimental decorators now requires
"experimentalDecorators": true
(#104)Previously esbuild would always compile decorators in TypeScript code using TypeScript's experimental decorator transform. Now that standard JavaScript decorators are close to being finalized, esbuild will now require you to use
"experimentalDecorators": true
to do this. This new requirement makes it possible for esbuild to introduce a transform for standard JavaScript decorators in TypeScript code in the future. Such a transform has not been implemented yet, however. -
TypeScript's
target
no longer affects esbuild'starget
(#2628)Some people requested that esbuild support TypeScript's
target
setting, so support for it was added (in version 0.12.4). However, esbuild supports reading from multipletsconfig.json
files within a single build, which opens up the possibility that different files in the build have different language targets configured. There isn't really any reason to do this and it can lead to unexpected results. So with this release, thetarget
setting intsconfig.json
will no longer affect esbuild's owntarget
setting. You will have to use esbuild's own target setting instead (which is a single, global value). -
TypeScript's
jsx
setting no longer causes esbuild to preserve JSX syntax (#2634)TypeScript has a setting called
jsx
that controls how to transform JSX into JS. The tool-agnostic transform is calledreact
, and the React-specific transform is calledreact-jsx
(orreact-jsxdev
). There is also a setting calledpreserve
which indicates JSX should be passed through untransformed. Previously people would run esbuild with"jsx": "preserve"
in theirtsconfig.json
files and then be surprised when esbuild preserved their JSX. So with this release, esbuild will now ignore"jsx": "preserve"
intsconfig.json
files. If you want to preserve JSX syntax with esbuild, you now have to use--jsx=preserve
.Note: Some people have suggested that esbuild's equivalent
jsx
setting override the one intsconfig.json
. However, some projects need to legitimately have different files within the same build use different transforms (i.e.react
vs.react-jsx
) and having esbuild's globaljsx
setting overridetsconfig.json
would prevent this from working. This release ignores"jsx": "preserve"
but still allows otherjsx
values intsconfig.json
files to override esbuild's globaljsx
setting to keep the ability for multiple files within the same build to use different transforms. -
useDefineForClassFields
behavior has changed (#2584, #2993)Class fields in TypeScript look like this (
x
is a class field):class Foo { x = 123 }
TypeScript has legacy behavior that uses assignment semantics instead of define semantics for class fields when
useDefineForClassFields
is enabled (in which case class fields in TypeScript behave differently than they do in JavaScript, which is arguably "wrong").This legacy behavior exists because TypeScript added class fields to TypeScript before they were added to JavaScript. The TypeScript team decided to go with assignment semantics and shipped their implementation. Much later on TC39 decided to go with define semantics for class fields in JavaScript instead. This behaves differently if the base class has a setter with the same name:
class Base { set x(_) { console.log('x:', _) } } // useDefineForClassFields: false class AssignSemantics extends Base { constructor() { super() this.x = 123 } } // useDefineForClassFields: true class DefineSemantics extends Base { constructor() { super() Object.defineProperty(this, 'x', { value: 123 }) } } console.log( new AssignSemantics().x, // Calls the setter new DefineSemantics().x // Doesn't call the setter )
When you run
tsc
, the value ofuseDefineForClassFields
defaults tofalse
when it's not specified and thetarget
intsconfig.json
is present but earlier thanES2022
. This sort of makes sense because the class field language feature was added in ES2022, so before ES2022 class fields didn't exist (and thus TypeScript's legacy behavior is active). However, TypeScript'starget
setting currently defaults toES3
which unfortunately means that theuseDefineForClassFields
setting currently defaults to false (i.e. to "wrong"). In other words if you runtsc
with all default settings, class fields will behave incorrectly.Previously esbuild tried to do what
tsc
did. That meant esbuild's version ofuseDefineForClassFields
wasfalse
by default, and was alsofalse
if esbuild's--target=
was present but earlier thanes2022
. However, TypeScript's legacy class field behavior is becoming increasingly irrelevant and people who expect class fields in TypeScript to work like they do in JavaScript are confused when they use esbuild with default settings. It's also confusing that the behavior of class fields would change if you changed the language target (even though that's exactly how TypeScript works).So with this release, esbuild will now only use the information in
tsconfig.json
to determine whetheruseDefineForClassFields
is true or not. SpecificallyuseDefineForClassFields
will be respected if present, otherwise it will befalse
iftarget
is present intsconfig.json
and isES2021
or earlier, otherwise it will betrue
. Targets passed to esbuild's--target=
setting will no longer affectuseDefineForClassFields
.Note that this means different directories in your build can have different values for this setting since esbuild allows different directories to have different
tsconfig.json
files within the same build. This should let you migrate your code one directory at a time without esbuild's--target=
setting affecting the semantics of your code. -
Add support for
verbatimModuleSyntax
from TypeScript 5.0TypeScript 5.0 added a new option called
verbatimModuleSyntax
that deprecates and replaces two older options,preserveValueImports
andimportsNotUsedAsValues
. SettingverbatimModuleSyntax
to true intsconfig.json
tells esbuild to not drop unused import statements. Specifically esbuild now treats"verbatimModuleSyntax": true
as if you had specified both"preserveValueImports": true
and"importsNotUsedAsValues": "preserve"
. -
Add multiple inheritance for
tsconfig.json
from TypeScript 5.0TypeScript 5.0 now allows multiple inheritance for
tsconfig.json
files. You can now pass an array of filenames via theextends
parameter and yourtsconfig.json
will start off containing properties from all of those configuration files, in order. This release of esbuild adds support for this new TypeScript feature. -
Remove support for
moduleSuffixes
(#2395)The community has requested that esbuild remove support for TypeScript's
moduleSuffixes
feature, so it has been removed in this release. Instead you can use esbuild's--resolve-extensions=
feature to select which module suffix you want to build with. -
Apply
--tsconfig=
overrides tostdin
and virtual files (#385, #2543)When you override esbuild's automatic
tsconfig.json
file detection with--tsconfig=
to pass a specifictsconfig.json
file, esbuild previously didn't apply these settings to source code passed via thestdin
API option or to TypeScript files from plugins that weren't in thefile
namespace. This release changes esbuild's behavior so that settings fromtsconfig.json
also apply to these source code files as well. -
Support
--tsconfig-raw=
in build API calls (#943, #2440)Previously if you wanted to override esbuild's automatic
tsconfig.json
file detection, you had to create a newtsconfig.json
file and pass the file name to esbuild via the--tsconfig=
flag. With this release, you can now optionally use--tsconfig-raw=
instead to pass the contents oftsconfig.json
to esbuild directly instead of passing the file name. For example, you can now use--tsconfig-raw={"compilerOptions":{"experimentalDecorators":true}}
to enable TypeScript experimental decorators directly using a command-line flag (assuming you escape the quotes correctly using your current shell's quoting rules). The--tsconfig-raw=
flag previously only worked with transform API calls but with this release, it now works with build API calls too. -
Ignore all
tsconfig.json
files innode_modules
(#276, #2386)This changes esbuild's behavior that applies
tsconfig.json
to all files in the subtree of the directory containingtsconfig.json
. In version 0.12.7, esbuild started ignoringtsconfig.json
files insidenode_modules
folders. The rationale is that people typically do this by mistake and that doing this intentionally is a rare use case that doesn't need to be supported. However, this change only applied to certain syntax-specific settings (e.g.jsxFactory
) but did not apply to path resolution settings (e.g.paths
). With this release, esbuild will now ignore alltsconfig.json
files innode_modules
instead of only ignoring certain settings. -
Ignore
tsconfig.json
when resolving paths withinnode_modules
(#2481)Previously fields in
tsconfig.json
related to path resolution (e.g.paths
) were respected for all files in the subtree containing thattsconfig.json
file, even within a nestednode_modules
subdirectory. This meant that a project'spaths
settings could potentially affect any bundled packages. With this release, esbuild will no longer usetsconfig.json
settings during path resolution inside nestednode_modules
subdirectories. -
Prefer
.js
over.ts
withinnode_modules
(#3019)The default list of implicit extensions that esbuild will try appending to import paths contains
.ts
before.js
. This makes it possible to bundle TypeScript projects that reference other files in the project using extension-less imports (e.g../some-file
to load./some-file.ts
instead of./some-file.js
). However, this behavior is undesirable withinnode_modules
directories. Some package authors publish both their original TypeScript code and their compiled JavaScript code side-by-side. In these cases, esbuild should arguably be using the compiled JavaScript files instead of the original TypeScript files because the TypeScript compilation settings for files within the package should be determined by the package author, not the user of esbuild. So with this release, esbuild will now prefer implicit.js
extensions over.ts
when searching for import paths withinnode_modules
.
These changes are intended to improve esbuild's compatibility with
tsc
and reduce the number of unfortunate behaviors regardingtsconfig.json
and esbuild. -
-
Add a workaround for bugs in Safari 16.2 and earlier (#3072)
Safari's JavaScript parser had a bug (which has now been fixed) where at least something about unary/binary operators nested inside default arguments nested inside either a function or class expression was incorrectly considered a syntax error if that expression was the target of a property assignment. Here are some examples that trigger this Safari bug:
❱ x(function (y = -1) {}.z = 2) SyntaxError: Left hand side of operator '=' must be a reference. ❱ x(class { f(y = -1) {} }.z = 2) SyntaxError: Left hand side of operator '=' must be a reference.
It's not clear what the exact conditions are that trigger this bug. However, a workaround for this bug appears to be to post-process your JavaScript to wrap any in function and class declarations that are the direct target of a property access expression in parentheses. That's the workaround that UglifyJS applies for this issue: mishoo/UglifyJS#2056. So that's what esbuild now does starting with this release:
// Original code x(function (y = -1) {}.z = 2, class { f(y = -1) {} }.z = 2) // Old output (with --minify --target=safari16.2) x(function(c=-1){}.z=2,class{f(c=-1){}}.z=2); // New output (with --minify --target=safari16.2) x((function(c=-1){}).z=2,(class{f(c=-1){}}).z=2);
This fix is not enabled by default. It's only enabled when
--target=
contains Safari 16.2 or earlier, such as with--target=safari16.2
. You can also explicitly enable or disable this specific transform (calledfunction-or-class-property-access
) with--supported:function-or-class-property-access=false
. -
Fix esbuild's TypeScript type declarations to forbid unknown properties (#3089)
Version 0.17.0 of esbuild introduced a specific form of function overloads in the TypeScript type definitions for esbuild's API calls that looks like this:
interface TransformOptions { legalComments?: 'none' | 'inline' | 'eof' | 'external' } interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> { legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined) } declare function transformSync<ProvidedOptions extends TransformOptions>(input: string, options?: ProvidedOptions): TransformResult<ProvidedOptions> declare function transformSync(input: string, options?: TransformOptions): TransformResult
This more accurately reflects how esbuild's JavaScript API behaves. The result object returned by
transformSync
only has thelegalComments
property if you passlegalComments: 'external'
:// These have type "string | undefined" transformSync('').legalComments transformSync('', { legalComments: 'eof' }).legalComments // This has type "string" transformSync('', { legalComments: 'external' }).legalComments
However, this form of function overloads unfortunately allows typos (e.g.
egalComments
) to pass the type checker without generating an error as TypeScript allows all objects with unknown properties to extendTransformOptions
. These typos result in esbuild's API throwing an error at run-time.To prevent typos during type checking, esbuild's TypeScript type definitions will now use a different form that looks like this:
type SameShape<Out, In extends Out> = In & { [Key in Exclude<keyof In, keyof Out>]: never } interface TransformOptions { legalComments?: 'none' | 'inline' | 'eof' | 'external' } interface TransformResult<ProvidedOptions extends TransformOptions = TransformOptions> { legalComments: string | (ProvidedOptions['legalComments'] extends 'external' ? never : undefined) } declare function transformSync<T extends TransformOptions>(input: string, options?: SameShape<TransformOptions, T>): TransformResult<T>
This change should hopefully not affect correct code. It should hopefully introduce type errors only for incorrect code.
-
Fix CSS nesting transform for pseudo-elements (#3119)
This release fixes esbuild's CSS nesting transform for pseudo-elements (e.g.
::before
and::after
). The CSS nesting specification says that the nesting selector does not work with pseudo-elements. This can be seen in the example below: esbuild does not carry the parent pseudo-element::before
through the nesting selector&
. However, that doesn't apply to pseudo-elements that are within the same selector. Previously esbuild had a bug where it considered pseudo-elements in both locations as invalid. This release changes esbuild to only consider those from the parent selector invalid, which should align with the specification:/* Original code */ a, b::before { &.c, &::after { content: 'd'; } } /* Old output (with --target=chrome90) */ a:is(.c, ::after) { content: "d"; } /* New output (with --target=chrome90) */ a.c, a::after { content: "d"; }
-
Forbid
&
before a type selector in nested CSSThe people behind the work-in-progress CSS nesting specification have very recently decided to forbid nested CSS that looks like
&div
. You will have to use eitherdiv&
or&:is(div)
instead. This release of esbuild has been updated to take this new change into consideration. Doing this now generates a warning. The suggested fix is slightly different depending on where in the overall selector it happened:▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error] example.css:2:3: 2 │ &input { │ ~~~~~ ╵ :is(input) CSS nesting syntax does not allow the "&" selector to come before a type selector. You can wrap this selector in ":is()" as a workaround. This restriction exists to avoid problems with SASS nesting, where the same syntax means something very different that has no equivalent in real CSS (appending a suffix to the parent selector). ▲ [WARNING] Cannot use type selector "input" directly after nesting selector "&" [css-syntax-error] example.css:6:8: 6 │ .form &input { │ ~~~~~~ ╵ input& CSS nesting syntax does not allow the "&" selector to come before a type selector. You can move the "&" to the end of this selector as a workaround. This restriction exists to avoid problems with SASS nesting, where the same syntax means something very different that has no equivalent in real CSS (appending a suffix to the parent selector).