#1779 RegEx replace with forward-lookahead does not work

[Markus]

Consider the following document

abcd
abxy
abcd
abxy

I want to replace every 'ab' that is not followed by a 'c' to be replaced by '12'.

Steps to reproduce:

1. Open Search/Replace (Ctrl+r)
2. Activate RegEx-Mode by clicking the button
3. Use search query "ab(?=[^c])"
4. Use replacement "12"
5. Search first occurrence using blue downarrow
6. Hit replace (red downarrow)

Expected result: second line changes to 12xy
Actual result: nothing changes

1. Hit replace all (red double downarrow)

Result: all correct occurrences are replaced (this is expected).

[Jan Sundermeyer]

@Tim/Benito:
the problem lies with following code:
if (hasOption(Replace) && again && !all)
if (m_regexp.exactMatch(m_cursor.selectedText())) {
replaceCursorText(backward);
updateReplacementOverlays();
replaceCount++;
}

Any suggestions on how to resolve this ?

[Tim Hoffmann]

A correct handling is not possible just from the selection because the lookahead context is missing.
Probably, one will have to

if regexp contains lookahead or lookbehind:
    rematch the line until you find a match that results in the same selection
    if found:
        perform substitution

[Tim Hoffmann]

fixed: hg 6097 (bbb0cbdf3d1e)

Side remark (semi-offtopic): Instead of a positive lookahead on a negated set ab(?=[^c]) you could have as well used a negative lookahead ab(?!c).

[Carsten Wartmann]

Hi,

not sure if this is good style, it seems for me the Bug is not fixed in texstudio-2.11.2-rc? Or it is another similar Bug, I suck at Regex... so...

   ABC DUF_GHI XYZ DAF-DOFGHU
   ABC DEF. GHI XYZ DAFTRE
   ABC DEF! GHI XYZDAFDHFDBF

Try to replace in the project (normal replace works!) with

RegEx: D.F (real expression is more complex)
Replace: XXX

Results in:

   ABC XXX__GHI XYZ  XXX-X-XXGHU
   ABC XXX.. GHI XYZ  XXXTRE
   ABC XXX!! GHI XYZZXXXXXXXXXXX

[Jan Sundermeyer]

works fine here
I am not sure, what in your example is supposed to erroneous.

[Carsten Wartmann]

There is a duplication of the last character after the replacement. Like"XXX__" where there should only one underscore. Even more weird at XXX-X-XXGHU which should be XXX-XXXGHU.
As I said, I suck at RegEx but replacing with the normal replace works, only if using the extended replace for all Docs/Project etc. shows this....

[Jan Sundermeyer]

fixed, please , in future, open new bug reports for different bugs, especially since you originally forgot to mention that this only happens in in multi-doc replace

[Carsten Wartmann]

Thanks Jan! Sorry for not beeing exact enough.

EDIT: Just found that it is a manually process.

--When will there be a binary? Is it a automatic process or does someone need to put it online manually?--

[Tim Hoffmann]

The build process has to be started manually by us. There will be a release in the near future.