From 1cfd5b8133ef041b35b7be8340cbef7a9a8d1d9a Mon Sep 17 00:00:00 2001
From: John Alanbrook <john@pockle.world>
Date: Wed, 25 Feb 2026 17:28:11 -0600
Subject: [PATCH] add hot reload to util

---
 internal/os.c    | 22 ++++++++++++++++++++++
 internal/shop.cm | 30 ++++++++++++++++++++++--------
 util.cm          |  3 ++-
 3 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/internal/os.c b/internal/os.c
index 6b99b1fd..5d7c0a70 100644
--- a/internal/os.c
+++ b/internal/os.c
@@ -703,6 +703,27 @@ static JSValue js_os_stack(JSContext *js, JSValue self, int argc, JSValue *argv)
   JS_RETURN(arr.val);
 }
 
+static JSValue js_os_unstone(JSContext *js, JSValue self, int argc, JSValue *argv) {
+  if (argc < 1) return JS_NULL;
+  JSValue obj = argv[0];
+  if (mist_is_blob(obj)) {
+    JSBlob *bd = (JSBlob *)chase(obj);
+    bd->mist_hdr = objhdr_set_s(bd->mist_hdr, false);
+    return obj;
+  }
+  if (JS_IsArray(obj)) {
+    JSArray *arr = JS_VALUE_GET_ARRAY(obj);
+    arr->mist_hdr = objhdr_set_s(arr->mist_hdr, false);
+    return obj;
+  }
+  if (mist_is_gc_object(obj)) {
+    JSRecord *rec = JS_VALUE_GET_RECORD(obj);
+    rec->mist_hdr = objhdr_set_s(rec->mist_hdr, false);
+    return obj;
+  }
+  return JS_NULL;
+}
+
 static const JSCFunctionListEntry js_os_funcs[] = {
   MIST_FUNC_DEF(os, platform, 0),
   MIST_FUNC_DEF(os, arch, 0),
@@ -731,6 +752,7 @@ static const JSCFunctionListEntry js_os_funcs[] = {
   MIST_FUNC_DEF(os, getenv, 1),
   MIST_FUNC_DEF(os, qbe, 1),
   MIST_FUNC_DEF(os, stack, 1),
+  MIST_FUNC_DEF(os, unstone, 1),
 };
 
 JSValue js_core_internal_os_use(JSContext *js) {
diff --git a/internal/shop.cm b/internal/shop.cm
index 1f98c20c..890c29e5 100644
--- a/internal/shop.cm
+++ b/internal/shop.cm
@@ -455,6 +455,7 @@ Shop.extract_commit_hash = function(pkg, response) {
 
 var open_dls = {}
 var package_dylibs = {}  // pkg -> [{file, symbol, dylib}, ...]
+var reload_hashes = {}   // cache_key -> content hash for reload change detection
 
 function open_dylib_cached(path) {
   var handle = open_dls[path]
@@ -1982,19 +1983,27 @@ Shop.file_reload = function(file)
 }
 
 Shop.module_reload = function(path, package) {
-  if (!Shop.is_loaded(path,package)) return
+  if (!Shop.is_loaded(path, package)) return false
 
-  // Clear the module info cache for this path
   var lookup_key = package ? package + ':' + path : ':' + path
-  module_info_cache[lookup_key] = null
+  var info = resolve_module_info(path, package)
+  if (!info) return false
 
-  // Invalidate package dylib cache so next resolve triggers rebuild
-  if (package) {
-    package_dylibs[package] = null
+  // Check if source actually changed
+  var mod_path = null
+  var source = null
+  var new_hash = null
+  if (info.mod_resolve) mod_path = info.mod_resolve.path
+  if (mod_path && fd.is_file(mod_path)) {
+    source = fd.slurp(mod_path)
+    new_hash = content_hash(stone(blob(text(source))))
+    if (reload_hashes[info.cache_key] == new_hash) return false
+    reload_hashes[info.cache_key] = new_hash
   }
 
-  var info = resolve_module_info(path, package)
-  if (!info) return
+  // Clear caches
+  module_info_cache[lookup_key] = null
+  if (package) package_dylibs[package] = null
 
   var cache_key = info.cache_key
   var old = use_cache[cache_key]
@@ -2003,13 +2012,18 @@ Shop.module_reload = function(path, package) {
   var newmod = get_module(path, package)
   use_cache[cache_key] = newmod
 
+  // Smart update: unstone -> merge -> re-stone to preserve references
   if (old && is_object(old) && is_object(newmod)) {
+    os.unstone(old)
     arrfor(array(newmod), function(k) { old[k] = newmod[k] })
     arrfor(array(old), function(k) {
       if (!(k in newmod)) old[k] = null
     })
+    stone(old)
     use_cache[cache_key] = old
   }
+
+  return true
 }
 
 function get_package_scripts(package)
diff --git a/util.cm b/util.cm
index 1135c111..564d71ec 100644
--- a/util.cm
+++ b/util.cm
@@ -1,5 +1,6 @@
 var shop = use('internal/shop')
 
 return {
-  file_reload: shop.file_reload
+  file_reload: shop.file_reload,
+  reload: shop.module_reload
 }
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