From 4f5dad383bb14ba63b938e73cc11638d00e17509 Mon Sep 17 00:00:00 2001
From: claude <claude@verso>
Date: Fri, 19 Jun 2026 15:49:50 +0000
Subject: [PATCH] fix(typst-preview): use persistent session to avoid Rc
 ownership panics
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Every call to renderToSvg({ artifactContent }) internally routes through
runWithSession, which calls session.free() after fn resolves. Because the JS
GC may still hold a reference to the first RenderSession wrapper, the next
render's Rc::try_unwrap() panics with 'attempted to take ownership of Rust
value while it was borrowed'.

Fix: use renderer.createModule(data) once to create a persistent RenderSession
that is never freed during the component's lifetime. Subsequent renders call
session.manipulateData({ action: 'reset', data }) (synchronous, no ownership
transfer) + session.renderToSvg({ container }) which routes through
withinOptionSession's renderSession fast-path — bypassing runWithSession and
its session.free() entirely.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../components/typst-wasm-preview.tsx         | 35 ++++++++++++-------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx b/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx
index 4d830e27b7..118abb8c6a 100644
--- a/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx
+++ b/services/web/frontend/js/features/typst-preview/components/typst-wasm-preview.tsx
@@ -8,7 +8,7 @@ import {
 } from 'react'
 import { useTranslation } from 'react-i18next'
 import { createTypstRenderer } from '@myriaddreamin/typst.ts'
-import type { TypstRenderer } from '@myriaddreamin/typst.ts'
+import type { TypstRenderer, RenderSession } from '@myriaddreamin/typst.ts'
 import rendererWasmUrl from '@myriaddreamin/typst-ts-renderer/pkg/typst_ts_renderer_bg.wasm'
 import { useLocalCompileContext } from '@/shared/context/local-compile-context'
 import { useEditorViewContext } from '@/features/ide-react/context/editor-view-context'
@@ -37,13 +37,16 @@ const TypstWasmPreview: FC = () => {
   const containerRef = useRef<HTMLDivElement>(null)
   const workerRef = useRef<Worker | null>(null)
   const rendererRef = useRef<TypstRenderer | null>(null)
+  // Persistent render session — created once, reused for all subsequent renders
+  // to avoid the Rust borrow/ownership panics that occur when runWithSession
+  // creates and frees a session on every render
+  const sessionRef = useRef<RenderSession | null>(null)
   const isReadyRef = useRef(false)
   const compileTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
   // If 'compiled' arrives before renderer is ready, buffer the latest vector data
   const pendingVectorRef = useRef<Uint8Array | null>(null)
-  // Prevent concurrent runWithSession calls which cause Rust aliasing errors
+  // Prevent concurrent renders
   const isRenderingRef = useRef(false)
-  // Latest pending render while one is in progress
   const renderQueueRef = useRef<Uint8Array | null>(null)
 
   const [status, setStatus] = useState<Status>('initializing')
@@ -57,8 +60,6 @@ const TypstWasmPreview: FC = () => {
       return
     }
 
-    // If a render is in progress, queue this data and return —
-    // the in-progress render will pick it up when it finishes
     if (isRenderingRef.current) {
       renderQueueRef.current = vectorData
       return
@@ -71,13 +72,20 @@ const TypstWasmPreview: FC = () => {
       dataToRender = null
 
       try {
-        // Use RenderByContentOptions: pass artifactContent directly instead of
-        // using runWithSession + manipulateData, which causes Rust aliasing errors
-        await renderer.renderToSvg({
-          format: 'vector',
-          artifactContent: data,
-          container,
-        })
+        let session = sessionRef.current
+        if (!session) {
+          // createModule creates a persistent session loaded with the vector data.
+          // It does NOT go through runWithSession, so there is no automatic free()
+          // and no Rc::try_unwrap ownership conflict between renders.
+          session = await (renderer as any).createModule(data) as RenderSession
+          sessionRef.current = session
+        } else {
+          // Reset existing session with new vector data — synchronous, no ownership transfer
+          session.manipulateData({ action: 'reset', data })
+        }
+        // renderToSvg with an existing renderSession bypasses runWithSession entirely
+        // (withinOptionSession short-circuits to fn(session) when renderSession is present)
+        await session.renderToSvg({ container })
         pendingVectorRef.current = null
         setStatus('ready')
         setErrorMsg('')
@@ -88,7 +96,6 @@ const TypstWasmPreview: FC = () => {
         isRenderingRef.current = false
       }
 
-      // Pick up any compile result that arrived while we were rendering
       if (renderQueueRef.current) {
         dataToRender = renderQueueRef.current
         renderQueueRef.current = null
@@ -135,6 +142,8 @@ const TypstWasmPreview: FC = () => {
       })
     return () => {
       cancelled = true
+      sessionRef.current = null
+      rendererRef.current = null
     }
   }, [doRender])