fish will be stuck when tring to TAB to complete the path in scp command

[c02y]

• fish, version 2.6.0
• CentOS 6.5 32-bit kernel 2.6.32-431.el6.i686
• $TERM xterm-256color

For example, when you are typing scp ~/Pu (with or without sudo) and hit TAB to complete the Public or anything in the path, fish will be be stuck for seconds.

This will happen even when sh -c 'env HOME=$(mktemp -d) fish' (without third-party customizations). But tab to complete works smoothly in bash-shell.

[ridiculousfish]

I hope Control-C recovers? Regardless I think we need to make completions interruptible.

[c02y]

Control-C will cancel the current command string in the shell prompt, not instantly but cancel it only when I hit it the fourth or fifth time depending on how quickly I hit the Control-C after tab. So I can say that it is still in interrupted status.

[zanchey]

Duplicate of #23, I think - although completing local files shouldn't be slow.

[faho]

Note that this is most likely due to __fish_print_hostnames being slow:

complete -c scp -d Hostname -n "commandline --cut-at-cursor --current-token | string match -v '*:*'" -a "
(__fish_print_hostnames):

(
	#Prepend any username specified in the completion to the hostname
	commandline -ct |sed -ne 's/\(.*@\).*/\1/p'
)(__fish_print_hostnames):
"

It tries to complete hostnames if there is no ":" in the token, by calling __fish_print_hostnames twice. Now, we have sped that up significantly via #4378 and 3b3bcc9, but calling it twice (and calling sed) is still unnecessary.

@c02y: You'll find that 2.7b1 is faster here, but I think we can do better still.

[faho]

@c02y: 60248e8 should improve this a bit further.

The biggest possible improvement I can see would be if we could stop completing hostnames altogether in your case (e.g. via seeing that the token can't be a valid hostname), but we'll leave that for later.

[c02y]

I'm currently using v2.7b1(the 2.7b1 branch), it is the same result, even without completing hostname like this(if I understood the "stop completing hostnames" correctly):

scp filen(TAB)

I tried to use tab to complete the files starting with filen, even there is only one file such as filename in the current directory, it will be interrupted for seconds.

---

UPDATE:

I tried to compile and install the latest code from git master branch which contains the 60248e8 commit, but there were some errors from configuration files since the version of fish is 2.6.0-750-ged0a57ff, so I executed fish using sh -c 'env HOME=$(mktemp -d) fish', scp was still interrupted for seconds, and there were errors after the interruption was gone:

in fish-shell git directory:

scp fi(TAB)

after seconds I got this:

scp ficd: The directory “/tmp/tmp.mOqbj3xFQP/.ssh” does not exist
Standard input (line 21):
            builtin cd $relative_path
            ^
in function “_recursive”
        called on standard input

in function “_ssh_include”
        called on line 2 of file /usr/share/fish/functions/__fish_print_hostnames.fish
        with parameter list “/tmp/tmp.mOqbj3xFQP/.ssh/config”

in command substitution
        called on line 0 of file /usr/share/fish/functions/__fish_print_hostnames.fish

in function “__fish_print_hostnames”
        called on line 2 of file /usr/share/fish/functions/__fish_complete_user_at_hosts.fish

in command substitution
        called on line 0 of file /usr/share/fish/functions/__fish_complete_user_at_hosts.fish

in function “__fish_complete_user_at_hosts”
        called on standard input

in command substitution
        called on standard input

[faho]

it is the same result

I would expect it to be a bit faster, at least. Not as fast as just completing local files, because it doesn't, but faster than 2.6.0.

Now, I don't believe there's a great solution to make figuring out hostnames faster, but we should be able to figure out that something can't be a hostname.

There's https://stackoverflow.com/questions/106179/regular-expression-to-match-dns-hostname-or-ip-address#106223, which provides the following regex:

ValidHostnameRegex = "^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\-]*[A-Za-z0-9])$";

However, that doesn't include IPv6 addresses (which here would also be completed via known_hosts, so they'd count as hostnames for this purpose), and IMHO looks overly complicated and restrictive.

So I'd propose something like ^[a-zA-Z0-9][a-zA-Z0-9._:-]*$ (i.e. start with an alphanumeric character and then consist of alphanumeric characters, dots, underlines, colons and dashes otherwise). We would then only attempt host completion if the current token matches that. (Well, username@that)

scp ficd: The directory “/tmp/tmp.mOqbj3xFQP/.ssh” does not exist

Yeah, __fish_print_hostnames uses cd internally but doesn't check if the dir actually exists.

[faho]

As it turns out, these completions hit some limitations in string, especially with large host lists. #4610 (merged as 2de38ef8bfd) should improve this by a factor of 3 or so. I can't see any other low-hanging fruit here (of course better performance is always nice), so I'm closing this.

[c02y]

Yes, it works smoothly like other commands such as ls. Thank you.