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Execution order of static field initialization and static initialization blocks is not kept under target: esnext and useDefineForClassFields: false #45574
Description
Bug Report
🔎 Search Terms
class static initializer block esnext useDefineForClassFields
🕗 Version & Regression Information
4.4.1-rc, 4.5.0-dev.20210825
Static Initialization Blocks was newly introduced in TS 4.4.
⏯ Playground Link
💻 Code
tsconfig.json
{
"compilerOptions": {
"target": "esnext",
"useDefineForClassFields": false
}
}Code
class A {
static foo = 123;
static {
console.log(this.foo); // should show 123
}
}🙁 Actual behavior
Following code is emitted. The line marked as // should show 123 would not print 123.
var _a;
class A {
static {
console.log(this.foo); // should show 123
}
}
_a = A;
A.foo = 123;🙂 Expected behavior
An emit such that execution order of the static field initialization and the static initialization block are kept.
static {}initialization blocks are evaluated in document order interleaved with static field initializers.
Activity
andrewbranch commentedon Aug 25, 2021
Ron Buckton (@rbuckton) should we consider static initialization blocks incompatible with
useDefineForClassFields: false, and/or error when they read static class fields under that setting?[-]Execution order of static field initialization and static initialization blocks is not kept under module: esnext and useDefineForClassFields: false[/-][+]Execution order of static field initialization and static initialization blocks is not kept under target: esnext and useDefineForClassFields: false[/+]rbuckton commentedon Aug 25, 2021
Possibly. Or, we can change the emit for
esnextwhenuseDefineForClassFieldsisfalseto perform the assignments inside of astatic {}block as well. I would caution that we only do that if there's already astatic {}block on the class, though, sincestatic {}is only shipping unflagged in the latest v8 currently. That way, you opt-in to usingstatic {}for static field initializers whenuseDefineForClassFieldsisfalseif you're explicitly using the syntax in your class (since you're assumed to be running the code in an engine that supports that syntax).So, for example, our downlevel emit for the above could be: