Find in Files: backreference in regex search and replace not working with newlines

[eduardZA]

Issue Type: Bug

Create a text file and add the following:

this is the first line of the document.
this is the second one.

In the document, search for this:

(this is the first line)( of the document.)(\nthis is the second)( one.)

Replace the text with this:

$1$3

This gives the expected result.

Follow the exact same procedure with the Find in Files dialog. This works in the absence of newline characters:

As soon as the search is extended to contain a multiline pattern, the backreferences are printed explicitly and not interpolated:

These types of replacements definitely worked in version 1.29 with much more complicated replace patterns, even using optional groups.

The results are the same regardless of whether "search.usePCRE2": true is set (originally released in 1.29, but deprecated in 1.37).

VS Code version: Code 1.38.1 (b37e54c, 2019-09-11T13:31:32.854Z)
OS version: Darwin x64 18.7.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz (8 x 2200)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_deferred_display_list: disabled_off skia_renderer: disabled_off surface_synchronization: enabled_on video_decode: enabled viz_display_compositor: disabled_off webgl: enabled webgl2: enabled
Load (avg)	3, 3, 2
Memory (System)	16.00GB (0.11GB free)
Process Argv	-psn_0_548998
Screen Reader	no
VM	0%

Extensions (14)

Extension	Author (truncated)	Version
vscode-css-formatter	aes	1.0.1
shell-snippets	cds	0.1.2
bracket-pair-colorizer	Coe	1.0.61
scala	dal	0.0.5
gitlens	eam	9.9.3
terraform	mau	1.4.0
rainbow-csv	mec	1.3.1
ecdc	mit	1.3.0
vscode-docker	ms-	0.7.0
Go	ms-	0.11.4
chef	Pen	0.7.1
ruby	reb	0.25.3
vscode-yaml	red	0.5.2
HCL	who	0.0.5

[elizabeth-dev]

Same here. Seems a duplicate of #80732, #80667, and #79924.

[KapitanOczywisty]

@ eduardZA Do you have the same behavior when there are multiple matches in single files?

Problem seems to be not present when 2 results shares any line.

[eduardZA]

@KapitanOczywisty, quite right:

It would seem as if matches separated by newlines are the ones struggling.

[roblourens]

Dupe of #80667