Proxies Removal: Handle conversion to liboverrides also for linked data.

So far linked proxies were just kept as-is, this is no longer an option.

Attempt to convert them into liboverrides as much as possible, though
some cases won't be supported:
- Appending proxies is broken since a long time, so conversion will fail
  here as well.
- When linking data, some cases will fail to convert properly. in
  particular, if the linked proxy object is not instanced in a scene
  (e.g. when linking a collection containing a proxy as an
  epty-instanced collection instead of a view-layer-instanced collection).

NOTE: converion when linking/appending is done unconditionnaly, option
to not convert on file load will be removed in next commit anyway.

Part of T91671.

source/blender/blenkernel/intern/blendfile_link_append.c

@@ -993,6 +993,24 @@ static int foreach_libblock_link_append_callback(LibraryIDLinkCallbackData *cb_d
 /** \name Library link/append code.
  * \{ */
 
+static void blendfile_link_append_proxies_convert(Main *bmain, ReportList *reports)
+{
+  BlendFileReadReport bf_reports = {.reports = reports};
+  BKE_lib_override_library_main_proxy_convert(bmain, &bf_reports);
+
+  if (bf_reports.count.proxies_to_lib_overrides_success != 0 ||
+      bf_reports.count.proxies_to_lib_overrides_failures != 0) {
+    BKE_reportf(
+        bf_reports.reports,
+        RPT_WARNING,
+        "Proxies have been removed from Blender (%d proxies were automatically converted "
+        "to library overrides, %d proxies could not be converted and were cleared). "
+        "Please consider re-saving any library .blend file with the newest Blender version.",
+        bf_reports.count.proxies_to_lib_overrides_success,
+        bf_reports.count.proxies_to_lib_overrides_failures);
+  }
+}
+
 void BKE_blendfile_append(BlendfileLinkAppendContext *lapp_context, ReportList *reports)
 {
   if (lapp_context->num_items == 0) {
@@ -1259,6 +1277,8 @@ void BKE_blendfile_append(BlendfileLinkAppendContext *lapp_context, ReportList *
   }
 
   BKE_main_id_newptr_and_tag_clear(bmain);
+
+  blendfile_link_append_proxies_convert(bmain, reports);
 }
 
 void BKE_blendfile_link(BlendfileLinkAppendContext *lapp_context, ReportList *reports)
@@ -1361,6 +1381,10 @@ void BKE_blendfile_link(BlendfileLinkAppendContext *lapp_context, ReportList *re
                                                        .active_collection = NULL};
     loose_data_instantiate(&instantiate_context);
   }
+
+  if ((lapp_context->params->flag & FILE_LINK) != 0) {
+    blendfile_link_append_proxies_convert(lapp_context->params->bmain, reports);
+  }
 }
 
 /** \} */

source/blender/blenkernel/intern/lib_override.c

@@ -1040,7 +1040,12 @@ bool BKE_lib_override_library_proxy_convert(Main *bmain,
 
   /* In some cases the instance collection of a proxy object may be local (see e.g. T83875). Not
    * sure this is a valid state, but for now just abort the overriding process. */
-  if (!ID_IS_OVERRIDABLE_LIBRARY(id_root)) {
+  if (!ID_IS_OVERRIDABLE_LIBRARY_HIERARCHY(id_root)) {
+    if (ob_proxy->proxy != NULL) {
+      ob_proxy->proxy->proxy_from = NULL;
+    }
+    id_us_min((ID *)ob_proxy->proxy);
+    ob_proxy->proxy = ob_proxy->proxy_group = NULL;
     return false;
   }
 
@@ -1058,12 +1063,12 @@ bool BKE_lib_override_library_proxy_convert(Main *bmain,
   DEG_id_tag_update(&ob_proxy->id, ID_RECALC_COPY_ON_WRITE);
 
   /* In case of proxy conversion, remap all local ID usages to linked IDs to their newly created
-   * overrides.
+   * overrides. Also do that for the IDs from the same lib as the proxy in case it is linked.
    * While this might not be 100% the desired behavior, it is likely to be the case most of the
    * time. Ref: T91711. */
   ID *id_iter;
   FOREACH_MAIN_ID_BEGIN (bmain, id_iter) {
-    if (!ID_IS_LINKED(id_iter)) {
+    if (!ID_IS_LINKED(id_iter) || id_iter->lib == ob_proxy->id.lib) {
       id_iter->tag |= LIB_TAG_DOIT;
     }
   }
@@ -1120,18 +1125,24 @@ void BKE_lib_override_library_main_proxy_convert(Main *bmain, BlendFileReadRepor
   }
 
   LISTBASE_FOREACH (Object *, object, &bmain->objects) {
-    if (ID_IS_LINKED(object)) {
-      if (object->proxy != NULL) {
-        CLOG_WARN(&LOG, "Did not try to convert linked proxy object '%s'", object->id.name);
-        reports->count.linked_proxies++;
-      }
-      continue;
-    }
-
     if (object->proxy_group != NULL || object->proxy != NULL) {
-      CLOG_WARN(
-          &LOG, "Proxy object '%s' failed to be converted to library override", object->id.name);
+      if (ID_IS_LINKED(object)) {
+        CLOG_WARN(&LOG,
+                  "Linked proxy object '%s' from '%s' failed to be converted to library override",
+                  object->id.name + 2,
+                  object->id.lib->filepath);
+      }
+      else {
+        CLOG_WARN(&LOG,
+                  "Proxy object '%s' failed to be converted to library override",
+                  object->id.name + 2);
+      }
       reports->count.proxies_to_lib_overrides_failures++;
+      if (object->proxy != NULL) {
+        object->proxy->proxy_from = NULL;
+      }
+      id_us_min((ID *)object->proxy);
+      object->proxy = object->proxy_group = NULL;
     }
   }
 }

source/blender/blenloader/BLO_readfile.h

@@ -117,8 +117,6 @@ typedef struct BlendFileReadReport {
     /* Number of root override IDs that were resynced. */
     int resynced_lib_overrides;
 
-    /* Number of (non-converted) linked proxies. */
-    int linked_proxies;
     /* Number of proxies converted to library overrides. */
     int proxies_to_lib_overrides_success;
     /* Number of proxies that failed to convert to library overrides. */

source/blender/windowmanager/intern/wm_files.c

@@ -874,18 +874,16 @@ static void file_read_reports_finalize(BlendFileReadReport *bf_reports)
                 duration_lib_override_recursive_resync_seconds);
   }
 
-  if (bf_reports->count.linked_proxies != 0 ||
-      bf_reports->count.proxies_to_lib_overrides_success != 0 ||
+  if (bf_reports->count.proxies_to_lib_overrides_success != 0 ||
       bf_reports->count.proxies_to_lib_overrides_failures != 0) {
-    BKE_reportf(bf_reports->reports,
-                RPT_WARNING,
-                "Proxies are deprecated (%d proxies were automatically converted to library "
-                "overrides, %d proxies could not be converted and %d linked proxies were kept "
-                "untouched). If you need to keep proxies for the time being, please disable the "
-                "`Proxy to Override Auto Conversion` in Experimental user preferences",
-                bf_reports->count.proxies_to_lib_overrides_success,
-                bf_reports->count.proxies_to_lib_overrides_failures,
-                bf_reports->count.linked_proxies);
+    BKE_reportf(
+        bf_reports->reports,
+        RPT_WARNING,
+        "Proxies have been removed from Blender (%d proxies were automatically converted "
+        "to library overrides, %d proxies could not be converted and were cleared). "
+        "Please also consider re-saving any library .blend file with the newest Blender version.",
+        bf_reports->count.proxies_to_lib_overrides_success,
+        bf_reports->count.proxies_to_lib_overrides_failures);
   }
 
   if (bf_reports->count.sequence_strips_skipped != 0) {