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[Bug] isCancel no longer narrows prompt results after 1.5.0 #600
Description
Environment
- OS: macOS
- Node Version: v24.20.0
- Package:
@clack/core,@clack/prompts - Package Version: core 1.5.0, prompts 1.8.0
Describe the bug
#592 changed isCancel from value is symbol to value is typeof CANCEL_SYMBOL, but every prompt still returns Promise<T | symbol> (core Prompt.prompt() and the 11 as Promise<... | symbol> casts in prompts). typescript can't subtract a unique symbol from symbol, so after the guard the result still has symbol in its type and any downstream use errors. this breaks code that type-checked fine on 1.7.0.
To Reproduce
import { path, isCancel } from '@clack/prompts';
const p = await path({ message: 'pick a file' });
if (isCancel(p)) process.exit(0);
console.log(`selected: ${p}`);
// TS2731: Implicit conversion of a 'symbol' to a 'string' will fail at runtime.same snippet passes on prompts 1.7.0 / core 1.4.3. assigning the result to a string fails with TS2322 instead.
Expected behavior
isCancel narrows the cancel case away like it did before. #554 asked for the specific cancel type on prompt return types, and #592 only did the guard half, which is what left the two out of sync.
Activity
43081j commentedon Sep 8, 2026
sad times.
i blame the LLM that pushed us to make that change 😞 may just close them in future
lets fix it in a patch. i think we can just update the prompts to return
T | typeof CANCEL_SYMBOLgameroman commentedon Sep 8, 2026
I wonder if we can just revert
isCanceltovalue is symbol?clack/packages/core/src/utils/index.ts
Line 17 in de1ef16
The reason they asked to export
CANCEL_SYMBOLin the original issue was for tests but the other 2 points about "broadsymboltype"43081j commentedon Sep 8, 2026
we can revert it but its technically more correct now than it was.
i.e. a prompt currently can't return any
symbolwithout breakingisCancel.so there's two options:
isCancel(what we had before)| typeof CANCEL_SYMBOLinstead of| symboli'm happy to go with whatever you two think is the most sensible one. only really a
selectcan produce a symbol today (select from a list of symbols), so its pretty low risk leaving it as it was (1)chore(deps): take @clack/prompts 1.8.1 and adapt to its cancel and va…
chore(deps): bump the npm-minor group with 2 updates (#502)