Multicursor highlighting on selection behaves oddly

[atombender]

• VSCode Version: 1.9.1

Steps to Reproduce:

1. Type the text XXXXXX
2. Select the first X
3. Hit cmd-D multiple times. The selection will grow exponentially:

I expected each cmd-D keypress to select the next X.

Furthermore, the "highlight all" behaves similarly oddly: It will highlight pairs of whatever you selected:

Even weirder, if you replace the text, then undo, any adjacent selections are collapsed (so it doesn't undo the selection properly):

1. Type 20 Zs.
2. Select one Z and "highlight all". There are now 10 selections of 2 characters each (wrong).
3. Type "p" to replacing all of them. You get 10 p's (wrong).
4. Undo. There are now 5 selections of 4 characters each (wrong).
5. Type "p" to replace all of them again. You get 5 p's (wrong).
6. And so on.

[roblourens]

The first might be expected since contiguous selections are combined. Second looks like a bug?

[atombender]

Well, I did not expect the first one.

There are practical implications beyond just being weird: With the above behaviour it's impossible to select all Xs unless they occur in powers of 2. I.e. I can select 1, 2, 4, 8, ... Xs, but not, say, 10.

As for selections being combined: If I have X X X X ... (i.e. separated by spaces), it works: All instances of X are individually selected. Logically, it shouldn't matter if the Xs are next to each other or not, since my starting selection is a single character.

In other words, the behaviour is inconsistent. Not just that, it's arguably useless, because it's extremely rare to want to replace exactly 2ⁿ instances of anything.

VSC does seem capable of having multiple selections adjacent to each other, as shown by the second example (the Ys).

[atombender]

Updated issue with a GIF of the third problem (affecting "highlight all").

[martin-sweeny]

I opened a similar issue... Possible duplicate of #11150 @alexandrudima

[atombender]

Looks like it's the same bug. Although mine demonstrates a few more edge cases that we'll want to keep in mind in whichever issue is kept open.

[paulpflug]

stumbled upon this, too. Usecase:

# replace all \n with newline
\n
\n\n
\n

currently not possible with ctrl+d, as selection changes from \n to \n\n on the second line

[alexdima]

Duplicate of #6661