Multiline LSP diagnostics send to neovim's API are unwrapped

[WhyNotHugo]

Information

VIM version

NVIM v0.10.2                                                                                                                             
Build type: MinSizeRel                                                                                                                   

Operating System: Alpine Linux, Edge

What went wrong

I'm using vim.g.ale_use_neovim_diagnostics_api = 1. When ALE sends diagnostics to neovim, ALE unwraps multiline diagnostics.

Some LSPs return multi-line diagnostics, and even align continuation lines to present the error in a visually clearer way. Joining lines breaks displaying of diagnostics in most interfaces.

Screenshots

The following compare how diagnostics from both sources, rendered via lsp_lines.nvim.

When using neovim with its native LSP client:

When using ALE:

Reproducing the bug

1. Enable ale_use_neovim_diagnostics_api
2. Open a go file with an error like strings.Replace("a", "b", 0) (note that the error returned by the LSP is multi-line, and continuation lines are deliberately aligned).

:ALEInfo

Expand

Current Filetype: go Available Linters: ['bingo', 'cspell', 'gobuild', 'gofmt', 'golangci-lint', 'gopls', 'gosimple', 'gotype', 'govet', 'golangserver', 'revive', 'staticcheck'] Linter Aliases: 'gobuild' -> ['go build'] 'govet' -> ['go vet'] Enabled Linters: [] Ignored Linters: [] Suggested Fixers: 'gofmt' - Fix Go files with go fmt. 'gofumpt' - Fix Go files with gofumpt, a stricter go fmt. 'goimports' - Fix Go files imports with goimports. 'golangci_lint' - Fix Go files with golangci-lint. 'golines' - Fix Go file long lines with golines 'gopls' - Fix Go files with gopls. 'remove_trailing_lines' - Remove all blank lines at the end of a file. 'trim_whitespace' - Remove all trailing whitespace characters at the end of every line.

Linter Variables:
" Press Space to read :help for a setting
let g:ale_go_go_executable = 'go'
let g:ale_go_golangci_lint_executable = 'golangci-lint'
let g:ale_go_golangci_lint_options = ''
let g:ale_go_golangci_lint_package = 0
let g:ale_go_langserver_executable = 'go-langserver'
let g:ale_go_langserver_options = ''

Global Variables:
" Press Space to read :help for a setting
let g:ale_cache_executable_check_failures = v:null
let g:ale_change_sign_column_color = v:null
let g:ale_command_wrapper = v:null
let g:ale_completion_delay = v:null
let g:ale_completion_enabled = 0
let g:ale_completion_max_suggestions = v:null
let g:ale_disable_lsp = 'auto'
let g:ale_echo_cursor = 1
let g:ale_echo_msg_error_str = 'Error'
let g:ale_echo_msg_format = v:null
let g:ale_echo_msg_info_str = 'Info'
let g:ale_echo_msg_warning_str = 'Warning'
let g:ale_enabled = 1
let g:ale_fix_on_save = 0
let g:ale_fixers = {'go': ['gofmt'], 'yaml': ['prettier'], 'scss': ['prettier'], 'json': ['prettier'], 'lua': ['stylua'], 'html': ['prettier'], 'vue': ['prettier'], '*': ['remove_trailing_lines', 'trim_whitespace'], 'typescript': ['prettier'], 'sql': ['pgformatter'], 'markdown': ['prettier']}
let g:ale_history_enabled = 1
let g:ale_info_default_mode = 'preview'
let g:ale_history_log_output = 1
let g:ale_keep_list_window_open = v:null
let g:ale_lint_delay = 200
let g:ale_lint_on_enter = 1
let g:ale_lint_on_filetype_changed = 1
let g:ale_lint_on_insert_leave = 1
let g:ale_lint_on_save = 1
let g:ale_lint_on_text_changed = 'normal'
let g:ale_linter_aliases = {}
let g:ale_linters = {'markdown': ['proselint', 'vale'], 'apkbuild': ['apkbuild_lint'], 'mail': ['proselint']}
let g:ale_linters_explicit = 1
let g:ale_linters_ignore = {}
let g:ale_list_vertical = v:null
let g:ale_list_window_size = v:null
let g:ale_loclist_msg_format = v:null
let g:ale_max_buffer_history_size = v:null
let g:ale_max_signs = v:null
let g:ale_maximum_file_size = v:null
let g:ale_open_list = v:null
let g:ale_pattern_options = v:null
let g:ale_pattern_options_enabled = v:null
let g:ale_root = {}
let g:ale_set_balloons = 0
let g:ale_set_highlights = 1
let g:ale_set_loclist = 1
let g:ale_set_quickfix = 0
let g:ale_set_signs = 1
let g:ale_sign_column_always = v:null
let g:ale_sign_error = v:null
let g:ale_sign_info = v:null
let g:ale_sign_offset = v:null
let g:ale_sign_style_error = v:null
let g:ale_sign_style_warning = v:null
let g:ale_sign_warning = v:null
let g:ale_sign_highlight_linenrs = v:null
let g:ale_type_map = v:null
let g:ale_use_neovim_diagnostics_api = 1
let g:ale_use_global_executables = v:null
let g:ale_virtualtext_cursor = 'disabled'
let g:ale_warn_about_trailing_blank_lines = 1
let g:ale_warn_about_trailing_whitespace = 1

Command History:

[WhyNotHugo]

I too unfamiliar with the codebase to figure out why this is happening, and can't think of useful keywords to search further.

Any pointers would be welcome.

[WhyNotHugo]

The following patch fixes the issue:

diff --git a/autoload/ale/lsp/response.vim b/autoload/ale/lsp/response.vim
index 498ec508..522ddb89 100644
--- a/autoload/ale/lsp/response.vim
+++ b/autoload/ale/lsp/response.vim
@@ -27,8 +27,9 @@ function! ale#lsp#response#ReadDiagnostics(response) abort
 
     for l:diagnostic in a:response.params.diagnostics
         let l:severity = get(l:diagnostic, 'severity', 0)
         let l:loclist_item = {
-        \   'text': substitute(l:diagnostic.message, '\(\r\n\|\n\|\r\)', ' ', 'g'),
+        \   'text': l:diagnostic.message,
         \   'type': 'E',
         \   'lnum': l:diagnostic.range.start.line + 1,
         \   'col': l:diagnostic.range.start.character + 1,

Diagnostics are rendered properly. I do have to further test this with other setups; I'm uncertain of how this displays in other contexts that are not using neovim's diagnostics API.

Small aside: when merging lines, leading indentation of continuation lines should be trimmed too.

[WhyNotHugo]

:ALEPopulateLocList seems to continue rendering fine ­— it merges consecutive lines into one, and also trims whitespace from each one before doing so, so the patch actually improves the loclist.