Error.prototype.stack の今と未来

私たちが普段の開発で何気なく見ている `Error` の stack trace は実は標準化されていません。
このトークでは `Error.prototype.stack` について、各 JavaScript Runtime の実装と、これを標準化しようとする動きを紹介します。

リンク集: https://gist.github.com/progfay/4d0a79eee4483ac34937a0e8af106acc

Transcript

1. 2025.11.16 | JSConf JP 2025 | @progfay `Error.prototype.stack`: Present & Future
2. ɾWeb Frontend Engineer ɾI like... ɾ🔍 Researching Web Trends ɾ🎤 Japanese Rap Name: Shunsuke Mano   @progfay
4. Error.prototype.stack - JavaScript | MDN
5. Let's deep dive into Error.prototype.stack !
6. V8
7. V8 v8/src/execution/messages.cc at 5ac61190087feaa7fda2284f9f06e227141444ee · v8/v8
8. V8 - Stack trace API Stack trace API · V8
9. Node.js node/lib/internal/errors.js at 622c3721bf61e0bda825bed821e316e19ba75eff · nodejs/node
10. Node.js
11. Deno
12. JSC
13. JSC WebKit/Source/JavaScriptCore/interpreter/Interpreter.cpp at 66754d9a9c19aa6402c09970adc0191c460980cc · WebKit/WebKit WebKit/Source/JavaScriptCore/runtime/StackFrame.cpp at 66754d9a9c19aa6402c09970adc0191c460980cc · WebKit/WebKit
14. JSC
15. Bun 🤯
16. Bun bun/src/bun.js/bindings/FormatStackTraceForJS.cpp at 0db90b25261d4379103a4574e722362ed52a31cc · oven-sh/bun
17. https://x.com/bunjavascript/status/1966814439744958941
18. SpiderMonkey
19. SpiderMonkey JS::BuildStackString (SavedStacks.cpp - mozsearch) - 45e3c8634099e0f57fa0e7660dba85580a5dd8e7
20. SpiderMonkey JS::FormatSpiderMonkeyStackFrame (SavedStacks.cpp - mozsearch) - 45e3c8634099e0f57fa0e7660dba85580a5dd8e7
21. SpiderMonkey
22. So many runtimes, so many stack formats...
23. It's time to standardize!
24. tc39/proposal-error-stacks - GitHub
25. proposal-error-stacks • ECMAScript Proposal, specs, and reference implementation for Error.prototype.stack / System.getStack / System.getStackString
26. proposal-error-stacks • ECMAScript Proposal, specs, and reference implementation for Error.prototype.stack / System.getStack / System.getStackString
27. I believe is this seems like too much, too big, not well motivated as a big proposal. Make we could split it up. やりすぎ、 大 きすぎ、根拠も不 十 分に 見 える。 分割しよう。 notes/meetings/2024-12/december-05.md at 3bb70e4b6745798dc145be6859c92a7a0b6d0100 · tc39/notes proposal-error-stacks EN JP
28. • getter: calc & cache formatted stack • setter: update cache V8's Error.prototype.stack is exotic! v8/src/execution/messages.cc at 740213e7e48558f16b6842bb74be0086ac2980d2 · v8/v8 v8/src/builtins/accessors.cc at 740213e7e48558f16b6842bb74be0086ac2980d2 · v8/v8 check cache & return if exists set cache
29. tc39/proposal-error-stack-accessor - GitHub
30. proposal-error-stack-accessor • focus Error.prototype.stack accessor (getter / setter) • the only requirement is that it return a string Spec - Error Stack Accessor
31. Conclusion • Present: So many runtime, so many stack format • Standardizing activity: proposal-error-stacks, proposal-error-stack-accessor • Future: runtimes may provide Structured stack frame There's long way to go...