3 files changed, 95 insertions, 7 deletions

diff --git a/extmod/vfs_posix.c b/extmod/vfs_posix.c
index 1505682f1..6df91a273 100644
--- a/extmod/vfs_posix.c
+++ b/extmod/vfs_posix.c
@@ -58,21 +58,23 @@ typedef struct _mp_obj_vfs_posix_t {
 } mp_obj_vfs_posix_t;
 
 STATIC const char *vfs_posix_get_path_str(mp_obj_vfs_posix_t *self, mp_obj_t path) {
-    if (self->root_len == 0) {
-        return mp_obj_str_get_str(path);
+    const char *path_str = mp_obj_str_get_str(path);
+    if (self->root_len == 0 || path_str[0] != '/') {
+        return path_str;
     } else {
-        self->root.len = self->root_len;
-        vstr_add_str(&self->root, mp_obj_str_get_str(path));
+        self->root.len = self->root_len - 1;
+        vstr_add_str(&self->root, path_str);
         return vstr_null_terminated_str(&self->root);
     }
 }
 
 STATIC mp_obj_t vfs_posix_get_path_obj(mp_obj_vfs_posix_t *self, mp_obj_t path) {
-    if (self->root_len == 0) {
+    const char *path_str = mp_obj_str_get_str(path);
+    if (self->root_len == 0 || path_str[0] != '/') {
         return path;
     } else {
-        self->root.len = self->root_len;
-        vstr_add_str(&self->root, mp_obj_str_get_str(path));
+        self->root.len = self->root_len - 1;
+        vstr_add_str(&self->root, path_str);
         return mp_obj_new_str(self->root.buf, self->root.len);
     }
 }
diff --git a/tests/extmod/vfs_posix_paths.py b/tests/extmod/vfs_posix_paths.py
new file mode 100644
index 000000000..8cdad7706
--- /dev/null
+++ b/tests/extmod/vfs_posix_paths.py
@@ -0,0 +1,73 @@
+# Test for VfsPosix with relative paths
+
+try:
+    import os
+
+    os.VfsPosix
+except (ImportError, AttributeError):
+    print("SKIP")
+    raise SystemExit
+
+# We need a directory for testing that doesn't already exist.
+# Skip the test if it does exist.
+temp_dir = "vfs_posix_paths_test_dir"
+try:
+    import os
+
+    os.stat(temp_dir)
+    print("SKIP")
+    raise SystemExit
+except OSError:
+    pass
+
+curdir = os.getcwd()
+os.mkdir(temp_dir)
+
+# construct new VfsPosix with absolute path argument
+temp_dir_abs = os.getcwd() + os.sep + temp_dir
+vfs = os.VfsPosix(temp_dir_abs)
+# when VfsPosix is used the intended way via os.mount(), it can only be called
+# with relative paths when the CWD is inside or at its root, so simulate that
+os.chdir(temp_dir_abs)
+vfs.mkdir("subdir")
+vfs.mkdir("subdir/one")
+print('listdir("/"):', sorted(i[0] for i in vfs.ilistdir("/")))
+print('listdir("."):', sorted(i[0] for i in vfs.ilistdir(".")))
+print('getcwd() in {"", "/"}:', vfs.getcwd() in {"", "/"})
+print('chdir("subdir"):', vfs.chdir("subdir"))
+print("getcwd():", vfs.getcwd())
+print('mkdir("two"):', vfs.mkdir("two"))
+f = vfs.open("file.py", "w")
+f.write("print('hello')")
+f.close()
+print('listdir("/"):', sorted(i[0] for i in vfs.ilistdir("/")))
+print('listdir("/subdir"):', sorted(i[0] for i in vfs.ilistdir("/subdir")))
+print('listdir("."):', sorted(i[0] for i in vfs.ilistdir(".")))
+try:
+    f = vfs.open("/subdir/file.py", "r")
+    print(f.read())
+    f.close()
+except Exception as e:
+    print(e)
+import sys
+
+sys.path.insert(0, "")
+try:
+    import file
+
+    print(file)
+except Exception as e:
+    print(e)
+del sys.path[0]
+vfs.remove("file.py")
+vfs.rmdir("two")
+vfs.rmdir("/subdir/one")
+vfs.chdir("/")
+vfs.rmdir("/subdir")
+
+# done with vfs, restore CWD
+os.chdir(curdir)
+
+# rmdir
+os.rmdir(temp_dir)
+print(temp_dir in os.listdir())
diff --git a/tests/extmod/vfs_posix_paths.py.exp b/tests/extmod/vfs_posix_paths.py.exp
new file mode 100644
index 000000000..5828453c9
--- /dev/null
+++ b/tests/extmod/vfs_posix_paths.py.exp
@@ -0,0 +1,13 @@
+listdir("/"): ['subdir']
+listdir("."): ['subdir']
+getcwd() in {"", "/"}: True
+chdir("subdir"): None
+getcwd(): subdir
+mkdir("two"): None
+listdir("/"): ['subdir']
+listdir("/subdir"): ['file.py', 'one', 'two']
+listdir("."): ['file.py', 'one', 'two']
+print('hello')
+hello
+<module 'file' from 'file.py'>
+False