fix: honor per-call async options when composing hooks - #4139

Marked version: master cdbdc0122ab83b2b97560944bf009a22cfb78b05 (18.1.1)

Markdown flavor: n/a — JavaScript hooks API

Description

Expectation

Calling parse(markdown, { async: true }) should await composed hooks and honor an async hook returning false to use the previous provider.

Result

Hook composition checks the instance default async flag instead of the active parse options. When async mode is enabled only on a parse call, an async hook passes a Promise into an earlier synchronous hook, or an async provider's false fallback is skipped. The parse rejects with errors such as markdown.toUpperCase is not a function.

What was attempted

Use the parse options already stored on the hooks object to select async composition. Add regressions for chained preprocess/postprocess hooks and an asynchronous parser-provider fallback while keeping the instance default synchronous.

Validation: all three regressions fail before the fix. Full npm test passes, including 1911 specification tests and 202 unit tests, build/docs, UMD/CJS smoke checks, types and lint. git diff --check passes.

Discovery and implementation: automated OpenAI gpt-6.1-sol source review, xhigh reasoning.

Contributor

• Tests exist to ensure functionality and minimize regression.
• This is a bug fix to existing async options; no new feature documentation is required.

Committer

• CI is green (pending after publication).
• Squash and Merge PR following conventional commit guidelines (maintainer action).