scan.go: scan() shall support adjacent quoting

[dumblob]

Currently it's impossible to write e.g. :select 'my'""'file' (not even :select 'my''file') to select the file myfile. This is needed for safe handling of files containing either control characters (see scan.go: scan(): case s.chr == '"': ... for the full list of them) or ' or both in their names.

I stumbled upon this when writing a safe lf command like this:

# won't work for files with ' in their name
cmd c1 &{{ lf -remote "send $id select '$f'" }}

[gokcehan]

@dumblob Quotes in lf are implemented differently than shell. You can use ' by quoting it in between " and control characters by escaping them with octal escapes between double quotes.

[dumblob]

Yeah, I saw the implementation, but I'm unable to find a way for the described issue. It also doesn't sound right to me to list all special cases (e.g. escape all control characters lf understands) by doing something like

cmd c1 &{{ lf -remote 'send '"$id"' select "'"$(sed -Ez -e 's|('"'"')|"\1"|g' -e 's|(\\)|"134"|g' -e '...for_each_ctrl_char' <<END
$f
END
)"'"' }}

(not even sure the code above will work)

as that's really not nice and in addition it's fragile (e.g. if lf will change it's behavior in this regards even slightly, there'll be a bug in the sed regex).

[gokcehan]

@dumblob How does concatenating strings solve the example you provided?

[dumblob]

One can easily guarantee (in a forward compatible manner) no control character nor any quote will get interpreted by something like:

cmd c1 &{{ lf -remote "send $id select '$( sed -Ez "s|'|'\"'\"'|g" <<END
$f
END
printf "'"  # this is to overcome subshell removing all trailing newlines (in case filename has trailing newline(s)
)" }}

I.e. filename abc' def will be transformed into'abc'"'"' def'.

[gokcehan]

@dumblob I still don't understand. You only escaped ' and did not do anything about control characters. If you want to escape ', you can already escape it within " with the current implementation.

[dumblob]

You only escaped ' and did not do anything about control characters.

The point is, that if one is inside of '' block, there are no control characters at all. So one needs to escape only the ' character itself. Or am I missing something?

[gokcehan]

@dumblob What about the control characters then?

[dumblob]

Inside of anything enclosed in single apostrophes ('), there are no control characters. That's how I read:

lf/scan.go

Lines 260 to 268 in 3c5abbb

	case s.chr == '\'':
	s.next()
	beg := s.off
	for !s.eof && s.chr != '\'' {
	s.next()
	}
	s.typ = tokenIdent
	s.tok = string(s.buf[beg:s.off])
	s.next()

[gokcehan]

@dumblob Weren't you trying to handle control characters in filenames? That is what you told in the beginning of the issue. If that's the case, why are you trying this with single quotes rather than double quotes?

[dumblob]

I meant control characters lf recognizes, but not control characters the terminal (emulator) or whatever else recognizes.

[dumblob]

Is there any better way than to support all currently implemented lf control characters as outlined above?

Let me demonstrate the issue with pure Go code.

s := "/path/with'so me/sep\" arat e's ingle'and double\" qu otes \"and arbitrary spaces"
//cmd := exec.Command( "lf", "-remote", "send 1234 select " + s )  // wrong
//cmd := exec.Command( "lf", "-remote", "send 1234 select '" + s + "'" )  // also wrong (actually impossible to achieve with single quotes at all)
//cmd := exec.Command( "lf", "-remote", "send 1234 select \"" + s + "\"" )  // also wrong (escaping of " and all control sequences is missing)

s = strings.ReplaceAll( s, "\\", "\\\\" )
s = strings.ReplaceAll( s, "\"", "\\\"" )
cmd := exec.Command( "lf", "-remote", "send 1234 select \"" + s + "\"" )  // finally right

With my proposal above this would be simpler and more forward compatible (I can imagine lf escape sequences changing or being extended, but I can't imagine the adjacent functionality being removed or changed):

s = strings.ReplaceAll( s, "'", "'\"'\"'" )
cmd := exec.Command( "lf", "-remote", "send 1234 select '" + s + "'" )

Shouldn't this issue stay open?