Fix T49775: Appending data with internal dependency cycles prevents correct clearing of linked data-blocks.

This is not a simple fix, but imho still needs to be backported to 2.78a...

3 files changed, 207 insertions, 76 deletions

diff --git a/source/blender/blenkernel/BKE_library_query.h b/source/blender/blenkernel/BKE_library_query.h
index c5f575c8c0f..c6b63754b57 100644
--- a/source/blender/blenkernel/BKE_library_query.h
+++ b/source/blender/blenkernel/BKE_library_query.h
@@ -88,4 +88,6 @@ bool BKE_library_ID_is_locally_used(struct Main *bmain, void *idv);
 bool BKE_library_ID_is_indirectly_used(struct Main *bmain, void *idv);
 void BKE_library_ID_test_usages(struct Main *bmain, void *idv, bool *is_used_local, bool *is_used_linked);
 
+void BKE_library_tag_unused_linked_data(struct Main *bmain, const bool do_init_tag);
+
 #endif  /* __BKE_LIBRARY_QUERY_H__ */
diff --git a/source/blender/blenkernel/intern/library.c b/source/blender/blenkernel/intern/library.c
index 8b09e51a2d3..14612151a8e 100644
--- a/source/blender/blenkernel/intern/library.c
+++ b/source/blender/blenkernel/intern/library.c
@@ -73,6 +73,8 @@
 
 #include "BLI_blenlib.h"
 #include "BLI_utildefines.h"
+#include "BLI_linklist.h"
+#include "BLI_memarena.h"
 
 #include "BLI_threads.h"
 #include "BLT_translation.h"
@@ -1644,6 +1646,10 @@ void BKE_library_make_local(Main *bmain, const Library *lib, const bool untagged
 	ID *id, *id_next;
 	int a;
 
+	LinkNode *copied_ids = NULL;
+	LinkNode *linked_loop_candidates = NULL;
+	MemArena *linklist_mem = BLI_memarena_new(256 * sizeof(copied_ids), __func__);
+
 	for (a = set_listbasepointers(bmain, lbarray); a--; ) {
 		id = lbarray[a]->first;
 
@@ -1653,6 +1659,7 @@ void BKE_library_make_local(Main *bmain, const Library *lib, const bool untagged
 
 		for (; id; id = id_next) {
 			id->newid = NULL;
+			id->tag &= ~LIB_TAG_DOIT;
 			id_next = id->next;  /* id is possibly being inserted again */
 
 			/* The check on the second line (LIB_TAG_PRE_EXISTING) is done so its
@@ -1675,6 +1682,10 @@ void BKE_library_make_local(Main *bmain, const Library *lib, const bool untagged
 						else {
 							id_make_local(bmain, id, false, true);
 						}
+
+						if (id->newid) {
+							BLI_linklist_prepend_arena(&copied_ids, id, linklist_mem);
+						}
 					}
 					else {
 						id->tag &= ~(LIB_TAG_EXTERN | LIB_TAG_INDIRECT | LIB_TAG_NEW);
@@ -1694,12 +1705,13 @@ void BKE_library_make_local(Main *bmain, const Library *lib, const bool untagged
 	/* We have to remap local usages of old (linked) ID to new (local) id in a second loop, as lbarray ordering is not
 	 * enough to ensure us we did catch all dependencies (e.g. if making local a parent object before its child...).
 	 * See T48907. */
-	for (a = set_listbasepointers(bmain, lbarray); a--; ) {
-		for (id = lbarray[a]->first; id; id = id->next) {
-			if (id->newid) {
-				BKE_libblock_remap(bmain, id, id->newid, ID_REMAP_SKIP_INDIRECT_USAGE);
-			}
-		}
+	for (LinkNode *it = copied_ids; it; it = it->next) {
+		id = it->link;
+
+		BLI_assert(id->newid != NULL);
+		BLI_assert(id->lib != NULL);
+
+		BKE_libblock_remap(bmain, id, id->newid, ID_REMAP_SKIP_INDIRECT_USAGE);
 	}
 
 	/* Third step: remove datablocks that have been copied to be localized and are no more used in the end...
@@ -1707,61 +1719,108 @@ void BKE_library_make_local(Main *bmain, const Library *lib, const bool untagged
 	bool do_loop = true;
 	while (do_loop) {
 		do_loop = false;
-		for (a = set_listbasepointers(bmain, lbarray); a--; ) {
-			for (id = lbarray[a]->first; id; id = id_next) {
-				id_next = id->next;
-				if (id->newid) {
-					bool is_local = false, is_lib = false;
-
-					BKE_library_ID_test_usages(bmain, id, &is_local, &is_lib);
-
-					/* Attempt to re-link copied proxy objects. This allows appending of an entire scene
-					 * from another blend file into this one, even when that blend file contains proxified
-					 * armatures that have local references. Since the proxified object needs to be linked
-					 * (not local), this will only work when the "Localize all" checkbox is disabled.
-					 * TL;DR: this is a dirty hack on top of an already weak feature (proxies). */
-					if (GS(id->name) == ID_OB && ((Object *)id)->proxy != NULL) {
-						Object *ob = (Object *)id;
-						Object *ob_new = (Object *)id->newid;
-
-						/* Proxies only work when the proxified object is linked-in from a library. */
-						if (ob->proxy->id.lib == NULL) {
-							printf("Warning, proxy object %s will loose its link to %s, because the "
-							       "proxified object is local.\n", id->newid->name, ob->proxy->id.name);
-						}
-						/* We can only switch the proxy'ing to a made-local proxy if it is no longer
-						 * referred to from a library. Not checking for local use; if new local proxy
-						 * was not used locally would be a nasty bug! */
-						else if (is_local || is_lib) {
-							printf("Warning, made-local proxy object %s will loose its link to %s, "
-							       "because the linked-in proxy is referenced (is_local=%i, is_lib=%i).\n",
-							       id->newid->name, ob->proxy->id.name, is_local, is_lib);
-						}
-						else {
-							/* we can switch the proxy'ing from the linked-in to the made-local proxy.
-							 * BKE_object_make_proxy() shouldn't be used here, as it allocates memory that
-							 * was already allocated by BKE_object_make_local_ex() (which called BKE_object_copy_ex). */
-							ob_new->proxy = ob->proxy;
-							ob_new->proxy_group = ob->proxy_group;
-							ob_new->proxy_from = ob->proxy_from;
-							ob_new->proxy->proxy_from = ob_new;
-							ob->proxy = ob->proxy_from = ob->proxy_group = NULL;
-						}
-					}
-					/* Special hack for groups... Thing is, since we can't instantiate them here, we need to ensure
-					 * they remain 'alive' (only instantiation is a real group 'user'... *sigh* See T49722. */
-					else if (GS(id->name) == ID_GR && (id->tag & LIB_TAG_INDIRECT) != 0) {
-						id_us_ensure_real(id->newid);
-					}
+		for (LinkNode *it = copied_ids; it; it = it->next) {
+			if ((id = it->link) == NULL) {
+				continue;
+			}
 
-					if (!is_local && !is_lib) {
-						BKE_libblock_free(bmain, id);
-						do_loop = true;
+			bool is_local = false, is_lib = false;
+
+			BKE_library_ID_test_usages(bmain, id, &is_local, &is_lib);
+
+			/* Attempt to re-link copied proxy objects. This allows appending of an entire scene
+			 * from another blend file into this one, even when that blend file contains proxified
+			 * armatures that have local references. Since the proxified object needs to be linked
+			 * (not local), this will only work when the "Localize all" checkbox is disabled.
+			 * TL;DR: this is a dirty hack on top of an already weak feature (proxies). */
+			if (GS(id->name) == ID_OB && ((Object *)id)->proxy != NULL) {
+				Object *ob = (Object *)id;
+				Object *ob_new = (Object *)id->newid;
+
+				/* Proxies only work when the proxified object is linked-in from a library. */
+				if (ob->proxy->id.lib == NULL) {
+					printf("Warning, proxy object %s will loose its link to %s, because the "
+						   "proxified object is local.\n", id->newid->name, ob->proxy->id.name);
+				}
+				/* We can only switch the proxy'ing to a made-local proxy if it is no longer
+				 * referred to from a library. Not checking for local use; if new local proxy
+				 * was not used locally would be a nasty bug! */
+				else if (is_local || is_lib) {
+					printf("Warning, made-local proxy object %s will loose its link to %s, "
+						   "because the linked-in proxy is referenced (is_local=%i, is_lib=%i).\n",
+						   id->newid->name, ob->proxy->id.name, is_local, is_lib);
+				}
+				else {
+					/* we can switch the proxy'ing from the linked-in to the made-local proxy.
+					 * BKE_object_make_proxy() shouldn't be used here, as it allocates memory that
+					 * was already allocated by BKE_object_make_local_ex() (which called BKE_object_copy_ex). */
+					ob_new->proxy = ob->proxy;
+					ob_new->proxy_group = ob->proxy_group;
+					ob_new->proxy_from = ob->proxy_from;
+					ob_new->proxy->proxy_from = ob_new;
+					ob->proxy = ob->proxy_from = ob->proxy_group = NULL;
+				}
+			}
+			/* Special hack for groups... Thing is, since we can't instantiate them here, we need to ensure
+			 * they remain 'alive' (only instantiation is a real group 'user'... *sigh* See T49722. */
+			else if (GS(id->name) == ID_GR && (id->tag & LIB_TAG_INDIRECT) != 0) {
+				id_us_ensure_real(id->newid);
+			}
+
+			if (!is_local) {
+				if (!is_lib) {  /* Not used at all, we can free it! */
+					BKE_libblock_free(bmain, id);
+					it->link = NULL;
+					do_loop = true;
+				}
+				else {  /* Only used by linked data, potential candidate to ugly lib-only dependency cycles... */
+					/* Note that we store the node, not directly ID pointer, that way if it->link is set to NULL
+					 * later we can skip it in lib-dependency cycles search later. */
+					BLI_linklist_prepend_arena(&linked_loop_candidates, it, linklist_mem);
+					id->tag |= LIB_TAG_DOIT;
+
+					/* Grrrrrrr... those half-datablocks-stuff... grrrrrrrrrrr...
+					 * Here we have to also tag them as potential candidates, otherwise they would falsy report
+					 * ID they used as 'directly used' in fourth step. */
+					ID *ntree = (ID *)ntreeFromID(id);
+					if (ntree != NULL) {
+						ntree->tag |= LIB_TAG_DOIT;
 					}
 				}
 			}
 		}
 	}
+
+	/* Fourth step: Try to find circle dependencies between indirectly-linked-only datablocks.
+	 * Those are fake 'usages' that prevent their deletion. See T49775 for nice ugly case. */
+	BKE_library_tag_unused_linked_data(bmain, false);
+	for (LinkNode *it = linked_loop_candidates; it; it = it->next) {
+		if (it->link == NULL) {
+			continue;
+		}
+		if ((id = ((LinkNode *)it->link)->link) == NULL) {
+			it->link = NULL;
+			continue;
+		}
+
+		/* Note: in theory here we are only handling datablocks forming exclusive linked dependency-cycles-based
+		 * archipelagos, so no need to check again after we have deleted one, as done in previous step. */
+		if (id->tag & LIB_TAG_DOIT) {
+			/* Note: *in theory* IDs tagged here are fully *outside* of file scope, totally unused, so we can
+			 *       directly wipe them out without caring about clearing their usages.
+			 *       However, this is a highly-risky presumption, and nice crasher in case something goes wrong here.
+			 *       So for 2.78a will keep the safe option, and switch to more efficient one in master later. */
+#if 0
+			BKE_libblock_free_ex(bmain, id, false);
+#else
+			BKE_libblock_unlink(bmain, id, false, false);
+			BKE_libblock_free(bmain, id);
+#endif
+			it->link = NULL;
+		}
+	}
+
+	BLI_memarena_free(linklist_mem);
 }
 
 /**
diff --git a/source/blender/blenkernel/intern/library_query.c b/source/blender/blenkernel/intern/library_query.c
index 08f9c439a7a..cec7fbacd80 100644
--- a/source/blender/blenkernel/intern/library_query.c
+++ b/source/blender/blenkernel/intern/library_query.c
@@ -1029,30 +1029,32 @@ static int foreach_libblock_id_users_callback(void *user_data, ID *self_id, ID *
 {
 	IDUsersIter *iter = user_data;
 
-	/* XXX This is actually some kind of hack...
-	 * Issue is, shapekeys' 'from' ID pointer is not actually ID usage.
-	 * Maybe we should even nuke it from BKE_library_foreach_ID_link, not 100% sure yet...
-	 */
-	if ((GS(self_id->name) == ID_KE) && (((Key *)self_id)->from == *id_p)) {
-		return IDWALK_RET_NOP;
-	}
-	/* XXX another hack, for similar reasons as above one. */
-	if ((GS(self_id->name) == ID_OB) && (((Object *)self_id)->proxy_from == (Object *)*id_p)) {
-		return IDWALK_RET_NOP;
-	}
+	if (*id_p) {
+		/* XXX This is actually some kind of hack...
+		 * Issue is, shapekeys' 'from' ID pointer is not actually ID usage.
+		 * Maybe we should even nuke it from BKE_library_foreach_ID_link, not 100% sure yet...
+		 */
+		if ((GS(self_id->name) == ID_KE) && (((Key *)self_id)->from == *id_p)) {
+			return IDWALK_RET_NOP;
+		}
+		/* XXX another hack, for similar reasons as above one. */
+		if ((GS(self_id->name) == ID_OB) && (((Object *)self_id)->proxy_from == (Object *)*id_p)) {
+			return IDWALK_RET_NOP;
+		}
 
-	if (*id_p && (*id_p == iter->id)) {
+		if (*id_p == iter->id) {
 #if 0
-		printf("%s uses %s (refcounted: %d, userone: %d, used_one: %d, used_one_active: %d, indirect_usage: %d)\n",
-		       iter->curr_id->name, iter->id->name, (cb_flag & IDWALK_USER) ? 1 : 0, (cb_flag & IDWALK_USER_ONE) ? 1 : 0,
-		       (iter->id->tag & LIB_TAG_EXTRAUSER) ? 1 : 0, (iter->id->tag & LIB_TAG_EXTRAUSER_SET) ? 1 : 0,
-		       (cb_flag & IDWALK_INDIRECT_USAGE) ? 1 : 0);
+			printf("%s uses %s (refcounted: %d, userone: %d, used_one: %d, used_one_active: %d, indirect_usage: %d)\n",
+				   iter->curr_id->name, iter->id->name, (cb_flag & IDWALK_USER) ? 1 : 0, (cb_flag & IDWALK_USER_ONE) ? 1 : 0,
+				   (iter->id->tag & LIB_TAG_EXTRAUSER) ? 1 : 0, (iter->id->tag & LIB_TAG_EXTRAUSER_SET) ? 1 : 0,
+				   (cb_flag & IDWALK_INDIRECT_USAGE) ? 1 : 0);
 #endif
-		if (cb_flag & IDWALK_INDIRECT_USAGE) {
-			iter->count_indirect++;
-		}
-		else {
-			iter->count_direct++;
+			if (cb_flag & IDWALK_INDIRECT_USAGE) {
+				iter->count_indirect++;
+			}
+			else {
+				iter->count_direct++;
+			}
 		}
 	}
 
@@ -1167,3 +1169,71 @@ void BKE_library_ID_test_usages(Main *bmain, void *idv, bool *is_used_local, boo
 	*is_used_local = (iter.count_direct != 0);
 	*is_used_linked = (iter.count_indirect != 0);
 }
+
+
+static int foreach_libblock_tag_unused_linked_data_callback(void *user_data, ID *self_id, ID **id_p, int UNUSED(cb_flag))
+{
+	bool *is_changed = user_data;
+
+	if (*id_p) {
+		/* XXX This is actually some kind of hack...
+		 * Issue is, shapekeys' 'from' ID pointer is not actually ID usage.
+		 * Maybe we should even nuke it from BKE_library_foreach_ID_link, not 100% sure yet...
+		 */
+		if ((GS(self_id->name) == ID_KE) && (((Key *)self_id)->from == *id_p)) {
+			return IDWALK_RET_NOP;
+		}
+		/* XXX another hack, for similar reasons as above one. */
+		if ((GS(self_id->name) == ID_OB) && (((Object *)self_id)->proxy_from == (Object *)*id_p)) {
+			return IDWALK_RET_NOP;
+		}
+
+		/* If checked id is used by an assumed used ID, then it is also used and not part of any linked archipelago. */
+		if (!(self_id->tag & LIB_TAG_DOIT) && ((*id_p)->tag & LIB_TAG_DOIT)) {
+			(*id_p)->tag &= ~LIB_TAG_DOIT;
+			*is_changed = true;
+		}
+	}
+
+	return IDWALK_RET_NOP;
+}
+
+/**
+ * Detect orphaned linked data blocks (i.e. linked data not used (directly or indirectly) in any way by any local data),
+ * including complex cases like 'linked archipelagoes', i.e. linked datablocks that use each other in loops,
+ * which prevents their deletion by 'basic' usage checks...
+ *
+ * \param do_init_tag if \a true, all linked data are checked, if \a false, only linked datablocks already tagged with
+ *                    LIB_TAG_DOIT are checked.
+ */
+void BKE_library_tag_unused_linked_data(Main *bmain, const bool do_init_tag)
+{
+	ListBase *lb_array[MAX_LIBARRAY];
+
+	if (do_init_tag) {
+		int i = set_listbasepointers(bmain, lb_array);
+
+		while (i--) {
+			for (ID *id = lb_array[i]->first; id; id = id->next) {
+				if (id->lib && (id->tag & LIB_TAG_INDIRECT) != 0) {
+					id->tag |= LIB_TAG_DOIT;
+				}
+				else {
+					id->tag &= ~LIB_TAG_DOIT;
+				}
+			}
+		}
+	}
+
+	bool do_loop = true;
+	while (do_loop) {
+		int i = set_listbasepointers(bmain, lb_array);
+		do_loop = false;
+
+		while (i--) {
+			for (ID *id = lb_array[i]->first; id; id = id->next) {
+				BKE_library_foreach_ID_link(id, foreach_libblock_tag_unused_linked_data_callback, &do_loop, IDWALK_NOP);
+			}
+		}
+	}
+}