Move input delimiter completion into the shared C++ core #1014

Summary

EnrichedMarkdownTextInput completes unclosed delimiters before parsing (**bold → **bold**) with three separate copies of the same loop: InputRemend.ts (web), InputRemend.kt (Android), ENRMInputRemend.mm (iOS). They have already drifted (web never got the #798 flanking check), and they share bugs that have to be fixed three times. All three parsers already reach the C++ core, so the completion step can live there once.

Bugs in today's loop

Where the display is rebuilt from the completed string (Android, web), these extra characters show up as literal text: the toolbar case re-imports as a b****** on web. iOS rebuilds the display from the original string and drops them (see #799).

Causes:

• A *** closer that does not match the * on top of the stack is pushed (or ignored) instead of closing * and then **. The output is also not idempotent: completing **rebase *interactive*** again appends more asterisks.
• Delimiters inside a code span are counted.

Proposal

One small function in packages/core/cpp, roughly today's algorithm plus:

• the md4c-style opener check from fix: input default values serialization #798 (isEmphasisOpener, intraword _ never opens) for *, _, ~~;
• * / _ runs close by length, popping several stack entries (*** closes * then **), so completion is idempotent;
• a backtick run skips to the matching equal-length run; an unmatched run is still closed.

Wiring:

• Android and web: a Md4cFlags field that makes MD4CParser.cpp complete the input before parsing (no new JNI method or wasm export, no second string copy into wasm).
• iOS: ENRMInputParser.mm calls the C++ function directly (it already compiles the core).
• Delete InputRemend.ts, InputRemend.kt, ENRMInputRemend.mm; move their tests to core ctest cases plus one parse-level test per platform.

This also removes a web import hot spot: completeMarkdown is the largest JS import cost today (3.7–4.8 ms per 63 KB); in C++ it runs inside the wasm parse call.

Related

• Align Android input display reconstruction with iOS (and drop the remend flanking heuristic) #799: rebuild the display from the original string on Android (as iOS does). Together with this issue, over-completion stops leaking on every platform; Align Android input display reconstruction with iOS (and drop the remend flanking heuristic) #799 alone would also allow dropping the flanking check.
• feat(core): C++ markdown repair module for streaming #830: core MarkdownRepair (remend port) for streaming. It fixes the cases above but is not usable for the input as is: its link handling drops or rewrites text (TextOnly drops a truncated link, Protocol inserts streamdown:incomplete-link, which would be serialized back), and with links off [**stable](https://git-scm gets its ** inside the URL. An "editor" profile there could replace this function later.

Out of scope

Escaping plain text in the serializer (5 * 2, a || b round trips).