go/parser: invalid block comment end position with CRLF line endings

[incansvl]

What version of Go, VS Code & VS Code Go extension are you using?

go: go1.15.4 windows/amd64
VSCode: 1.51.0
Extension: 0.18.1
Env:

set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\coev\AppData\Local\go-build
set GOENV=C:\Users\coev\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\coev\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\coev\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=C:\Users\coev\Documents\Development\eprom\go.mod
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\coev\AppData\Local\Temp\go-build248616018=/tmp/go-build -gno-record-gcc-switches

Share the Go related settings you have added/edited

{
    "go.useLanguageServer": true
}

(Note: the above is strange, because in the extension settings UI the option "Go: Use Language Server" is NOT selected?? However toggling this setting does not change the behaviour of the bug)

Describe the bug

Starting with a go file that includes a section of code commented out as a block with /* and */, when I save the file VSCode alters the file before saving corrupting the code. This does not happen if the code does not contain the block comment.

Expected behaviour: Save the code as displayed

Steps to reproduce the behavior:

1. Set up VSCode with the Go 0.18.1 extension (bug reproduced both with and without other extensions loaded)
2. Rename the test case file "vscode_go_save_bug_before_saving.go.txt" to remove the ".txt" extension and open it
3. Save the file (File->Save or ctrl-S)
4. The file is damaged BEFORE save, so it is corrupted both on disk and on screen in the editor. The result is shons in file vscode_go_save_bug_after_saving.go.txt (again, remove the .txt extension)

vscode_go_save_bug_before_saving.go.txt
vscode_go_save_bug_after_saving.go.txt

[stamblerre]

What is the output of gopls version?

[incansvl]

I had already upgraded the gopls extension by the time I saw your reply, so I'm afraid I don't know what version it was originally.

Having run the Go: Install/Update Tools command I thought the console said the plugin had been updated to v1.51.1, however a few minutes later, after a few unsuccessful test-saves of the test go file, I go a prompt to upgrade gopls, but the "upgrade" then said it had installed v0.5.3, so I now realise the 1.51.1 must have been the version of VSCode itself.

None of these changes have fixed the original problem, VSCodeis still mangling the file sytax whenever a go file with a block comment is saved. I checked, and commenting out the same block with multiple "//" single line comment rather than the "/* */" block comments works ok, so it does seem to be the block comment syntax that is the issue.

I also tried disabling the gopls "Use Language Server" setting. If I disable this in BOTH the Workspace and User settings, then saving works as expected, but if gopls is enabled in either setting the problem manifests.

[stamblerre]

Thank you for following up--I was able to reproduce this with CRLF line endings. You can try changing your line endings (in the right bottom corner of the VS Code window) to LF to avoid this problem in the meantime (gofmt defaults to LF anyway).

[stamblerre]

This appears to be another instance of a go/parser bug with CRLF line endings. See the repro case here: https://play.golang.org/p/4Sb0-kywzTw. The parser reports that the comment ends 2 lines above its actual end.

Related to #41197.

/cc @findleyr

[incansvl]

I'm using a Windows machine for this development so it will be using CRLF line endings by default I expect. I will try changing to LF.

I have been seeing other code-altering behaviours too, such as include statements (quite possibly erroneous ones as i'm new to Go coding) being deleted on save. Maybe there is a "correct by deleting" default behaviour in the auto-linter I'm not aware of.

[gopherbot]

Change https://golang.org/cl/270879 mentions this issue: internal/lsp: fix end positions for multi-line comments with CRLF lines