Fix: Multiline input broken in Julia executable folds

[Parth-Garg2629]

Fix: Multiline input broken in Julia executable folds

**Closes #14 **

---

🐛 Problem

Multiline Julia code inside executable folds (Insert → Fold → Executable) was silently broken — all lines were concatenated into a single line before being sent to the Julia process, causing multi-statement blocks to fail.

Example of broken behaviour:

A fold containing:

using Random
Random.seed!(42)
rand()

Was being serialised and sent to Julia as the single line:

using Random Random.seed!(42) rand()

which raises a parse error or produces wrong results.

---

🔍 Root Cause

The two lines at the bottom of progs/init-julia.scm:

(when (supports-julia?)
  (plugin-input-converters julia))

were the culprit. Even when called with no conversion rules, the macro plugin-input-converters registers the plugin name into the plugin-input-converters% logic group (in plugin-convert.scm):

(tm-define-macro (plugin-input-converters name2 . l)
  (let ((name (if (string? name2) name2 (symbol->string name2))))
    (lazy-input-converter-force name)
    (logic-group plugin-input-converters% ,name)   ;; ← always runs
    `(logic-rules ,@(plugin-input-converters-rules name l))))

The predicate plugin-supports-math-input-ref checks exactly this group:

(tm-define (plugin-supports-math-input-ref key)
  (lazy-input-converter-force key)
  (logic-in? key plugin-input-converters%))        ;; ← returns #t after the call above

Once plugin-supports-math-input-ref returns #t for "julia", plugin-preprocess (in plugin-eval.scm) routes the entire input tree through plugin-math-input:

(if (and (== (car opts) :math-input)
         (plugin-supports-math-input-ref name))
    (set! t (plugin-math-input (list 'tuple name t))))

plugin-math-input flattens the TeXmacs document tree into a single math expression, stripping every newline in the process. This is what destroyed the multiline structure of Julia code cells.

---

✅ Fix

Remove the (when (supports-julia?) (plugin-input-converters julia)) block entirely.

Julia already registers a custom serializer (julia-serialize) via (:serializer ,julia-serialize) in plugin-configure. That serializer calls texmacs->code with "SourceCode" style and appends the <EOF> sentinel correctly — it handles the full document tree, preserving newlines. Math-input pre-processing is therefore not needed and must be kept disabled.

A detailed explanatory comment has been added in place of the removed code to prevent future regressions.

---

📂 Files Changed

File	Change
progs/init-julia.scm	Removed (when (supports-julia?) (plugin-input-converters julia)); added a detailed explanatory comment

---

🧪 How to Test

1. Install the plugin and open TeXmacs / Mogan.

2. Go to Insert → Fold → Executable → Julia.

3. Enter a multiline Julia block, e.g.:

   using Random
   Random.seed!(42)
   rand()

4. Execute the fold.

Before this fix: All lines are collapsed into one; Julia raises a parse or runtime error.
After this fix: Each line is preserved; Julia returns a reproducible random float (e.g., 0.6293451231426089).

---

📎 References

• Reported in: mgubi/tm-julia#12
• Relevant TeXmacs source files:
  • TeXmacs/progs/utils/plugins/plugin-convert.scm — defines plugin-input-converters macro and plugin-supports-math-input-ref
  • TeXmacs/progs/utils/plugins/plugin-eval.scm — defines plugin-preprocess which reads plugin-supports-math-input-ref

[Parth-Garg2629]

@mgubi @hammerfunctor could u please review my PR