tools/mpremote: Fix absolute path usage in remote mounted VFS.

Prior to this fix the current working path in the remote VFS would always
be prepended to the requested path to get the full path, even if the
requested path was already absolute, ie starting with "/".

So `os.chdir("/remote/dir1")` would set the working path to "/dir1/", and
a subsequent call with an absolute path like `os.listdir("/remote/dir2")`
would try to list the directory "/dir1/dir2/".

Fixes issue micropython#15308.

Signed-off-by: Damien George <[email protected]>

Author: dpgeorge

tools/mpremote/mpremote/transport_serial.py

@@ -838,6 +838,9 @@ class RemoteFS:
     def __init__(self, cmd):
         self.cmd = cmd
 
+    def _abspath(self, path):
+        return path if path.startswith("/") else self.path + path
+
     def mount(self, readonly, mkfs):
         pass
 
@@ -859,7 +862,7 @@ def getcwd(self):
     def remove(self, path):
         c = self.cmd
         c.begin(CMD_REMOVE)
-        c.wr_str(self.path + path)
+        c.wr_str(self._abspath(path))
         res = c.rd_s32()
         c.end()
         if res < 0:
@@ -868,8 +871,8 @@ def remove(self, path):
     def rename(self, old, new):
         c = self.cmd
         c.begin(CMD_RENAME)
-        c.wr_str(self.path + old)
-        c.wr_str(self.path + new)
+        c.wr_str(self._abspath(old))
+        c.wr_str(self._abspath(new))
         res = c.rd_s32()
         c.end()
         if res < 0:
@@ -878,7 +881,7 @@ def rename(self, old, new):
     def mkdir(self, path):
         c = self.cmd
         c.begin(CMD_MKDIR)
-        c.wr_str(self.path + path)
+        c.wr_str(self._abspath(path))
         res = c.rd_s32()
         c.end()
         if res < 0:
@@ -887,7 +890,7 @@ def mkdir(self, path):
     def rmdir(self, path):
         c = self.cmd
         c.begin(CMD_RMDIR)
-        c.wr_str(self.path + path)
+        c.wr_str(self._abspath(path))
         res = c.rd_s32()
         c.end()
         if res < 0:
@@ -896,7 +899,7 @@ def rmdir(self, path):
     def stat(self, path):
         c = self.cmd
         c.begin(CMD_STAT)
-        c.wr_str(self.path + path)
+        c.wr_str(self._abspath(path))
         res = c.rd_s8()
         if res < 0:
             c.end()
@@ -912,7 +915,7 @@ def stat(self, path):
     def ilistdir(self, path):
         c = self.cmd
         c.begin(CMD_ILISTDIR_START)
-        c.wr_str(self.path + path)
+        c.wr_str(self._abspath(path))
         res = c.rd_s8()
         c.end()
         if res < 0:
@@ -933,7 +936,7 @@ def next():
     def open(self, path, mode):
         c = self.cmd
         c.begin(CMD_OPEN)
-        c.wr_str(self.path + path)
+        c.wr_str(self._abspath(path))
         c.wr_str(mode)
         fd = c.rd_s8()
         c.end()