Solve two annoying problems with ftp URLs for Jack: when repeated

retrieving files from the same host and directory, you had to close
the previous instance before opening a new one; and retrieving a
non-existent file would return an empty file.  (The latter fix relies
on maybe an undocumented property of NLST -- NLST of a file returns
just that file, while NLST of a non-existent file returns nothing.  A
side effect, unfortunately, seems to be that now ftp-retrieving an
*empty* directory may fail.  Ah well.)

diff --git a/Lib/urllib.py b/Lib/urllib.py
index a16529a5fc61a84f94cb1cbd3d28dcf226183d9d..b9a82d169211213f9fd153c3bcb59ba7815f099c 100644 (file)
--- a/Lib/urllib.py
+++ b/Lib/urllib.py
@@ -497,6 +497,7 @@ class ftpwrapper:
                self.init()
        def init(self):
                import ftplib
+               self.busy = 0
                self.ftp = ftplib.FTP()
                self.ftp.connect(self.host, self.port)
                self.ftp.login(self.user, self.passwd)
@@ -504,6 +505,7 @@ class ftpwrapper:
                        self.ftp.cwd(dir)
        def retrfile(self, file, type):
                import ftplib
+               self.endtransfer()
                if type in ('d', 'D'): cmd = 'TYPE A'; isdir = 1
                else: cmd = 'TYPE ' + type; isdir = 0
                try:
@@ -513,6 +515,13 @@ class ftpwrapper:
                        self.ftp.voidcmd(cmd)
                conn = None
                if file and not isdir:
+                       # Use nlst to see if the file exists at all
+                       try:
+                               self.ftp.nlst(file)
+                       except ftplib.error_perm, reason:
+                               raise IOError, ('ftp error', reason), \
+                                     sys.exc_info()[2]
+                       # Try to retrieve as a file
                        try:
                                cmd = 'RETR ' + file
                                conn = self.ftp.transfercmd(cmd)
@@ -525,13 +534,18 @@ class ftpwrapper:
                        if file: cmd = 'LIST ' + file
                        else: cmd = 'LIST'
                        conn = self.ftp.transfercmd(cmd)
+               self.busy = 1
                return addclosehook(conn.makefile('rb'), self.endtransfer)
        def endtransfer(self):
+               if not self.busy:
+                       return
+               self.busy = 0
                try:
                        self.ftp.voidresp()
                except ftperrors():
                        pass
        def close(self):
+               self.endtransfer()
                try:
                        self.ftp.close()
                except ftperrors():