From e1f6b33dfd0efa14e3c784b0e0eb4ffdeaebb583 Mon Sep 17 00:00:00 2001
From: Richard Higgins <richard@relh.net>
Date: Mon, 20 Jul 2026 21:58:20 -0700
Subject: [PATCH] Fix Emscripten request cancellation

Keep the native fetch handle so cancellation and deadlines can stop the request. Mark the request complete before closing it because Emscripten calls the error callback during an in-flight close.
---
 src/windy/platforms/emscripten/platform.nim | 29 ++++++++++++++-------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/src/windy/platforms/emscripten/platform.nim b/src/windy/platforms/emscripten/platform.nim
index 2871f16..9a802e9 100644
--- a/src/windy/platforms/emscripten/platform.nim
+++ b/src/windy/platforms/emscripten/platform.nim
@@ -36,7 +36,6 @@ type
     requestBody: string
     deadline: float64
     startTime: float64
-    canceled: bool
     completed: bool
 
     onError: HttpErrorCallback
@@ -101,6 +100,13 @@ proc close*(window: Window) =
 proc closeRequested*(window: Window): bool =
   return false
 
+proc abortFetch(state: EmsHttpRequestState) =
+  let fetch = state.fetch
+  if fetch == nil:
+    return
+  state.fetch = nil
+  emscripten_fetch_close(fetch)
+
 proc pollHttp() =
   ## Poll HTTP requests.
   let now = epochTime()
@@ -109,6 +115,7 @@ proc pollHttp() =
     if state.completed: continue
     if state.deadline > 0 and state.deadline <= now:
       state.completed = true
+      state.abortFetch()
       if state.onError != nil:
         state.onError("Deadline exceeded")
   var expiredSockets: seq[WebSocketHandle]
@@ -711,8 +718,10 @@ proc getState(fetch: ptr emscripten_fetch_t): EmsHttpRequestState =
 
 proc onFetchSuccess(fetch: ptr emscripten_fetch_t) {.cdecl.} =
   let state = getState(fetch)
-  if state == nil: return
+  if state == nil or state.completed:
+    return
   state.completed = true
+  state.fetch = nil
   var response = HttpResponse()
   response.code = int(fetch.status)
   if fetch.numBytes > 0 and fetch.data != nil:
@@ -726,8 +735,10 @@ proc onFetchSuccess(fetch: ptr emscripten_fetch_t) {.cdecl.} =
 
 proc onFetchError(fetch: ptr emscripten_fetch_t) {.cdecl.} =
   let state = getState(fetch)
-  if state == nil: return
+  if state == nil or state.completed:
+    return
   state.completed = true
+  state.fetch = nil
   if state.onError != nil:
     var msg = $fetch.status & " "
     for c in fetch.statusText:
@@ -738,7 +749,7 @@ proc onFetchError(fetch: ptr emscripten_fetch_t) {.cdecl.} =
 
 proc onFetchProgress(fetch: ptr emscripten_fetch_t) {.cdecl.} =
   let state = getState(fetch)
-  if state == nil: return
+  if state == nil or state.completed: return
   if state.onDownloadProgress != nil:
     let completed = int(fetch.dataOffset + fetch.numBytes)
     let total = (if fetch.totalBytes == 0: -1 else: int(fetch.totalBytes))
@@ -796,17 +807,15 @@ proc startHttpRequest*(
   # Headers array (optional): omit for now to avoid pointer array complexities
   attr.requestHeaders = nil
 
-  discard emscripten_fetch(addr attr, url.cstring)
+  state.fetch = emscripten_fetch(addr attr, url.cstring)
   result = handle
 
 proc cancel*(handle: HttpRequestHandle) {.raises: [].} =
   ## Cancel an HTTP request.
   let state = httpRequests.getOrDefault(handle, nil)
-  if state == nil: return
-  state.canceled = true
-  # There is no direct cancel from C API here; closing will abort if still active
-  if state.fetch != nil:
-    emscripten_fetch_close(state.fetch)
+  if state == nil or state.completed: return
+  state.completed = true
+  state.abortFetch()
 
 proc deadline*(handle: HttpRequestHandle): float64 =
   ## Get the deadline of an HTTP request.