os: rework mv so it works with different partitions (add fallback to os.mv_by_cp + tests) (#17065)

vlib/os/os.c.v

@@ -211,9 +211,9 @@ pub fn file_size(path string) u64 {
 	return 0
 }
 
-// mv moves files or folders from `src` to `dst`.
-// if you are not sure that the source and target are on the same mount/partition use mv_by_cp
-pub fn mv(src string, dst string) ! {
+// rename renames the file or folder from `src` to `dst`.
+// Use mv to move or rename a file in a platform independent manner.
+pub fn rename(src string, dst string) ! {
 	mut rdst := dst
 	if is_dir(rdst) {
 		rdst = join_path_single(rdst.trim_right(path_separator), file_name(src.trim_right(path_separator)))

vlib/os/os.v

@@ -126,6 +126,11 @@ pub fn mv_by_cp(source string, target string) ! {
 	rm(source)!
 }
 
+// mv moves files or folders from `src` to `dst`.
+pub fn mv(source string, target string) ! {
+	rename(source, target) or { mv_by_cp(source, target)! }
+}
+
 // read_lines reads the file in `path` into an array of lines.
 [manualfree]
 pub fn read_lines(path string) ![]string {

vlib/os/os_js.js.v

@@ -123,6 +123,20 @@ pub fn cp(src string, dst string) ! {
 	}
 }
 
+pub fn rename(src string, dst string) ! {
+	$if js_node {
+		err := ''
+		#try {
+		#$fs.renameSync(src.str,dst.str);
+		#return;
+		#} catch (e) {
+		#err.str = 'failed to rename ' + src.str + ' to ' + dst.str + ': ' + e.toString();
+		#}
+
+		return error(err)
+	}
+}
+
 pub fn read_file(s string) !string {
 	mut err := ''
 	err = err

vlib/os/os_test.v

@@ -930,3 +930,63 @@ fn test_reading_from_empty_file() {
 	assert content_bytes.len == 0
 	os.rm(empty_file)!
 }
+
+fn move_across_partitions_using_function(f fn (src string, dst string) !) ! {
+	bindfs := os.find_abs_path_of_executable('bindfs') or {
+		eprintln('skipping test_mv_by_cp, because bindfs was not present')
+		return
+	}
+	// eprintln('>> $bindfs')
+	pfolder := os.join_path(tfolder, 'parent')
+	cfolder := os.join_path(pfolder, 'child')
+	mfolder := os.join_path(pfolder, 'mountpoint')
+	cdeepfolder := os.join_path(cfolder, 'deep', 'folder')
+	os.mkdir_all(mfolder)!
+	os.mkdir_all(cfolder)!
+	os.mkdir_all(cdeepfolder)!
+	//
+	original_path := os.join_path(pfolder, 'original.txt')
+	target_path := os.join_path(cdeepfolder, 'target.txt')
+	os.write_file(original_path, 'text')!
+	os.write_file(os.join_path(cdeepfolder, 'x.txt'), 'some text')!
+	// os.system('tree $pfolder')
+	/*
+	/tmp/v_1000/v/tests/os_test/parent
+	├── child
+	│   └── deep
+	│       └── folder
+	│           └── x.txt
+	├── mountpoint
+	└── original.txt
+	*/
+	os.system('${bindfs} --no-allow-other ${cfolder} ${mfolder}')
+	defer {
+		os.system('sync; umount ${mfolder}')
+	}
+	// os.system('tree $pfolder')
+	/*
+	/tmp/v_1000/v/tests/os_test/parent
+	├── child
+	│   └── deep
+	│       └── folder
+	│           └── x.txt
+	├── mountpoint
+	│   └── deep
+	│       └── folder
+	│           └── x.txt
+	└── original.txt
+	*/
+
+	f(original_path, target_path)!
+
+	assert os.exists(target_path)
+	assert !os.exists(original_path)
+}
+
+fn test_mv_by_cp_across_partitions() {
+	move_across_partitions_using_function(os.mv_by_cp)!
+}
+
+fn test_mv_across_partitions() {
+	move_across_partitions_using_function(os.mv)!
+}