Workaround Fuse-T behavior on macOS

build.sh

@@ -47,6 +47,12 @@ case "$os" in
 	plat_files="$plat_files ../src/compat/dummy.c"
 	plat_files="$plat_files ../src/compat/clearenv.c "
 	plat_cflags="$plat_cflags -include ../src/compat/macosx.h"
+	# Fuse-T (kext-free FUSE) uses NFS internally, which stats every
+	# directory entry after readdir. Compile in a runtime check for
+	# this behavior that activates a workaround.
+	if [ "$server" = "fuse" ]; then
+		plat_cflags="$plat_cflags -DFUSE_NFS_WORKAROUND"
+	fi
 	default_cc=clang
 	;;
 	FreeBSD)

src/tup/file.c

@@ -27,6 +27,7 @@
 #include "config.h"
 #include "entry.h"
 #include "option.h"
+#include "pel_group.h"
 #include <stdio.h>
 #include <string.h>
 #include <fcntl.h>
@@ -62,6 +63,8 @@ int init_file_info(struct file_info *info, int do_unlink)
 	tent_tree_init(&info->used_groups_root);
 	tent_tree_init(&info->output_root);
 	tent_tree_init(&info->exclusion_root);
+	RB_INIT(&info->readdir_sticky);
+	RB_INIT(&info->open_readdir_sticky);
 	pthread_mutex_init(&info->lock, NULL);
 	pthread_cond_init(&info->cond, NULL);
 	info->server_fail = 0;
@@ -72,6 +75,8 @@ int init_file_info(struct file_info *info, int do_unlink)
 
 void cleanup_file_info(struct file_info *info)
 {
+	free_string_tree(&info->open_readdir_sticky);
+	free_string_tree(&info->readdir_sticky);
 	free_tent_tree(&info->exclusion_root);
 	free_tent_tree(&info->output_root);
 	free_tent_tree(&info->used_groups_root);
@@ -816,18 +821,32 @@ static int update_write_info(FILE *f, tupid_t cmdid, struct file_info *info,
 
 		map = TAILQ_FIRST(&info->mapping_list);
 
-		/* TODO: strcmp only here for win32 support */
-		if(strcmp(map->tmpname, map->realname) != 0) {
-			if(renameat(tup_top_fd(), map->tmpname, tup_top_fd(), map->realname) < 0) {
-				perror(map->realname);
-				fprintf(f, "tup error: Unable to rename temporary file '%s' to destination '%s'\n", map->tmpname, map->realname);
+		if(is_appledouble(map->realname)) {
+			/* macOS NFS / Fuse-T creates "._<name>" AppleDouble
+			 * sidecars next to any file with xattrs. They reach
+			 * us via the FUSE create path, so a tmpfile was
+			 * already opened — discard it instead of putting an
+			 * unwanted artifact in the source tree.
+			 */
+			if(unlinkat(tup_top_fd(), map->tmpname, 0) < 0 && errno != ENOENT) {
+				perror(map->tmpname);
+				fprintf(f, "tup error: Unable to remove AppleDouble tmp file '%s'\n", map->tmpname);
 				write_bork = 1;
 			}
-		}
-		if(map->tent) {
-			/* tent may not be set (in the case of hidden files) */
-			if(file_set_mtime(map->tent, map->realname) < 0)
-				return -1;
+		} else {
+			/* TODO: strcmp only here for win32 support */
+			if(strcmp(map->tmpname, map->realname) != 0) {
+				if(renameat(tup_top_fd(), map->tmpname, tup_top_fd(), map->realname) < 0) {
+					perror(map->realname);
+					fprintf(f, "tup error: Unable to rename temporary file '%s' to destination '%s'\n", map->tmpname, map->realname);
+					write_bork = 1;
+				}
+			}
+			if(map->tent) {
+				/* tent may not be set (in the case of hidden files) */
+				if(file_set_mtime(map->tent, map->realname) < 0)
+					return -1;
+			}
 		}
 		del_map(&info->mapping_list, map);
 	}

src/tup/file.h

@@ -27,6 +27,7 @@
 #include "tupid_tree.h"
 #include "tent_tree.h"
 #include "thread_tree.h"
+#include "string_tree.h"
 #include "pel_group.h"
 #include "entry.h"
 #include <stdio.h>
@@ -70,6 +71,8 @@ struct file_info {
 	struct tent_entries used_groups_root;
 	struct tent_entries output_root;
 	struct tent_entries exclusion_root;
+	struct string_entries readdir_sticky;
+	struct string_entries open_readdir_sticky;
 	int server_fail;
 	int open_count;
 	int do_unlink;

src/tup/pel_group.c

@@ -29,6 +29,25 @@
 
 static _Thread_local struct mempool pool = MEMPOOL_INITIALIZER(struct path_element);
 
+int is_appledouble(const char *path)
+{
+	/* macOS writes AppleDouble sidecar files ("._<name>") next to any
+	 * file with extended attributes when the underlying filesystem
+	 * doesn't store xattrs natively — notably Fuse-T's NFS-backed
+	 * mount used by tup itself. They are an OS-level side effect, not
+	 * a build output. Accepts both leading-slash FUSE paths and
+	 * relative paths (e.g. peeled `realname`s).
+	 */
+	if(path[0] == '.' && path[1] == '_')
+		return 1;
+	while((path = strchr(path, '/')) != NULL) {
+		if(path[1] == '.' && path[2] == '_')
+			return 1;
+		path++;
+	}
+	return 0;
+}
+
 int pel_ignored(const char *path, int len)
 {
 	if(len < 0)

src/tup/pel_group.h

@@ -43,6 +43,7 @@ struct pel_group {
 
 void init_pel_group(struct pel_group *pg);
 int pel_ignored(const char *path, int len);
+int is_appledouble(const char *path);
 int get_path_elements(const char *dir, struct pel_group *pg);
 void free_pel(struct path_element *pel);
 void del_pel(struct path_element *pel, struct pel_group *pg);

src/tup/server/Tupfile

@@ -3,6 +3,12 @@ include_rules
 ifeq ($(TUP_SERVER),fuse)
 export PKG_CONFIG_PATH
 CFLAGS += `pkg-config fuse --cflags`
+ifeq (@(TUP_PLATFORM),macosx)
+# Fuse-T (kext-free FUSE) uses NFS internally, which stats every
+# directory entry after readdir. Compile in a runtime check for
+# this behavior that activates a workaround.
+CFLAGS += -DFUSE_NFS_WORKAROUND
+endif
 : foreach fuse_server.c fuse_fs.c master_fork.c symlink.c |> !cc |>
 endif