fix(follow-link): resolve+open definitions ourselves on the Vim clients

The Vim follow-link path delegated to the LSP client's jump UI
(:LspDefinition / coc jumpDefinition), which broke two ways for wiki
link-following:

1. **No create-on-follow (vim-lsp + coc).** vim-lsp's location handler
   readfile()s the target to build a quickfix entry; for a not-yet-created
   page that throws E484 and aborts the jump, so <CR> on [[NewPage]] did
   nothing. The server was correct throughout — textDocument/definition
   returns a *synthesised* location for missing pages (verified over
   JSON-RPC).
2. **Wrong window placement (coc).** Without an explicit open command coc
   fell back to coc.preferences.jumpCommand (e.g. a tab command).

Stop delegating: nuwiki#commands#follow_link_or_create() /
follow_link_drop() now resolve textDocument/definition directly and open
the URI themselves via a shared s:open_definition(open_cmd) helper — :edit
for <CR>, `tab drop` for <C-S-CR>. :edit opens a buffer for a missing path
(save creates it, matching vimwiki) and gives exact current-window
placement regardless of the user's coc jumpCommand. Removes
s:jump_definition / s:drop_from_response.

Also fix the coc action name: CocAction('getDefinition') does not exist
(E605 "Action getDefinition does not exist") — the registered action is
'definitions'. Fixed in s:open_definition and badd_link.

coc config delivery: the setup guidance shipped without
initializationOptions, so coc users never sent wiki_root and the server
resolved links against its default root (existing pages flagged broken,
follow-to-create landed in the cwd). The printed snippet
(autoload/nuwiki/lsp.vim) now emits initializationOptions populated with
the resolved settings, and the README coc snippet documents it as required.

Add development/start-vim-coc.sh — a coc.nvim dev launcher (sibling of
start-vim.sh) that wires coc's prebuilt release branch + a generated
coc-settings.json (with initializationOptions), deliberately omitting
vim-lsp so the coc path is exercised; doubles as a reproducer.

Tests: new cr.follow_opens_missing_page_in_current_window case in
test-keymaps-vim.vim (stubs CocAction to a missing page, asserts
current-window :edit). Keymap suite 254+18 green; config-parity (Vim +
Neovim) green. Neovim path unchanged and re-confirmed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

development/start-vim-coc.sh

@@ -0,0 +1,178 @@
+#!/usr/bin/env bash
+#
+# start-vim-coc.sh — launch Vim with a minimal config that loads nuwiki
+# through coc.nvim (instead of vim-lsp).
+#
+# The plugin's Vim path (autoload/nuwiki/lsp.vim) prefers `vim-lsp` and falls
+# back to `coc.nvim`. start-vim.sh exercises the vim-lsp path; this script
+# exercises the coc.nvim path. vim-lsp is deliberately kept OFF the runtimepath
+# so `:LspDefinition` doesn't exist and nuwiki's coc branch is the one that runs
+# (s:jump_definition() → CocActionAsync('jumpDefinition', 'edit')).
+#
+# This doubles as a reproducer for the "<CR> opens a new tab" regression:
+# coc-settings.json sets coc.preferences.jumpCommand to `tabe`, so without the
+# fix `<CR>` on a link opens a new tab. With the fix nuwiki passes 'edit'
+# explicitly and the target opens in the *current* window regardless.
+#
+# It clones coc.nvim's prebuilt `release` branch into the dev cache on first
+# run (no yarn/build needed — it just needs Node.js at runtime).
+#
+# Usage: ./development/start-vim-coc.sh [extra args...]
+#   ./development/start-vim-coc.sh                       # open the scratch wiki's index
+#   ./development/start-vim-coc.sh path/to/note.wiki     # open a specific file
+#   NUWIKI_DEV_WIKI=/tmp/foo ./development/start-vim-coc.sh
+#   NUWIKI_DEV_NO_SEED=1 ./development/start-vim-coc.sh       # use WIKI_DIR as-is (no scratch seeding)
+#   NUWIKI_DEV_SKIP_BUILD=1 ./development/start-vim-coc.sh    # reuse the cached binary
+#   NUWIKI_DEV_COC_JUMP=edit ./development/start-vim-coc.sh   # change coc.preferences.jumpCommand
+#
+# The release binary is rebuilt on every launch so source changes always reach
+# the running LSP. `cargo build --release` is incremental, so this is a fast
+# no-op when nothing changed. Set NUWIKI_DEV_SKIP_BUILD=1 to skip the build.
+#
+# Tested with Vim 9.1+ and Node 18+. State (viminfo/sessions, coc data) lives
+# under $XDG_CACHE_HOME/nuwiki-dev/ so your real Vim install stays untouched.
+
+set -euo pipefail
+
+# Shared paths + helpers (log, ensure_binary, write_sample_wiki, seed_wiki).
+source "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/_common.sh"
+
+VIMRC="$DEV_DIR/vimrc-coc"
+VIM_STATE="$DEV_DIR/vim-coc-state"
+COC_DIR="$DEV_DIR/coc.nvim"
+COC_DATA="$DEV_DIR/coc-data"
+COC_SETTINGS="$DEV_DIR/coc-settings.json"
+COC_JUMP="${NUWIKI_DEV_COC_JUMP:-tabe}"
+
+ensure_node() {
+  if ! command -v node >/dev/null 2>&1; then
+    log 'node not found — coc.nvim needs Node.js at runtime; skipping'
+    exit 0
+  fi
+}
+
+ensure_coc() {
+  mkdir -p "$DEV_DIR"
+  if [[ -d "$COC_DIR/.git" ]]; then
+    return
+  fi
+  if ! command -v git >/dev/null 2>&1; then
+    log 'git not found — cannot clone coc.nvim; skipping'
+    exit 0
+  fi
+  log "cloning coc.nvim (release branch) → $COC_DIR"
+  git clone --depth 1 --branch release \
+    https://github.com/neoclide/coc.nvim.git "$COC_DIR" >/dev/null 2>&1
+}
+
+write_coc_settings() {
+  mkdir -p "$DEV_DIR"
+  # Mirror what the vim-lsp client sends (autoload/nuwiki/lsp.vim s:settings()):
+  # both `initializationOptions` (sent on initialize) and `settings.nuwiki`
+  # (served via workspace/configuration). Without these the server falls back
+  # to its own default wiki_root (~/vimwiki) instead of $WIKI_DIR, so it can't
+  # resolve links (e.g. Notes shows as broken) or create-on-follow correctly.
+  cat > "$COC_SETTINGS" <<EOF
+{
+  "coc.preferences.jumpCommand": "$COC_JUMP",
+  "languageserver": {
+    "nuwiki": {
+      "command": "$REPO_ROOT/bin/nuwiki-ls",
+      "filetypes": ["vimwiki"],
+      "initializationOptions": {
+        "wiki_root": "$WIKI_DIR",
+        "file_extension": ".wiki",
+        "syntax": "vimwiki",
+        "log_level": "info",
+        "diagnostic": { "link_severity": "warn" }
+      },
+      "settings": {
+        "nuwiki": {
+          "wiki_root": "$WIKI_DIR",
+          "file_extension": ".wiki",
+          "syntax": "vimwiki",
+          "log_level": "info",
+          "diagnostic": { "link_severity": "warn" }
+        }
+      }
+    }
+  }
+}
+EOF
+}
+
+write_vimrc() {
+  mkdir -p "$DEV_DIR"
+  cat > "$VIMRC" <<EOF
+" start-vim-coc.sh: generated minimal config for nuwiki development (coc.nvim).
+" Regenerated on every launch; edit start-vim-coc.sh, not this file.
+
+" Confine state to the dev cache so we never touch the user's real Vim
+" install.
+set viminfo='100,n$VIM_STATE/viminfo
+let &directory = '$VIM_STATE/swap//'
+let &backupdir = '$VIM_STATE/backup//'
+let &undodir = '$VIM_STATE/undo//'
+
+" Make Vim look for runtime paths in the dev cache. vim-lsp is intentionally
+" absent so nuwiki dispatches jump-to-definition through coc.
+set nocompatible
+let &runtimepath = '$REPO_ROOT' . ',' . &runtimepath
+let &runtimepath .= ',$COC_DIR'
+
+" Point coc at the generated settings + a private data dir.
+let g:coc_config_home = '$DEV_DIR'
+let g:coc_data_home   = '$COC_DATA'
+
+let g:nuwiki_binary_path  = '$REPO_ROOT/bin/nuwiki-ls'
+let g:nuwiki_wiki_root    = '$WIKI_DIR'
+let g:nuwiki_file_extension = '.wiki'
+let g:nuwiki_syntax       = 'vimwiki'
+let g:nuwiki_log_level    = 'info'
+
+filetype plugin indent on
+syntax enable
+set hidden
+set termguicolors
+set number
+set signcolumn=yes
+set noswapfile
+set nobackup
+set nowritebackup
+let mapleader = ' '
+
+" Auto-detect filetype for .wiki files (the plugin ships ftdetect, but
+" --clean disables those — copy the rule here).
+augroup NuwikiFtdetect
+  autocmd!
+  autocmd BufRead,BufNewFile *.wiki setfiletype vimwiki
+augroup END
+
+" coc starts the server automatically from coc-settings.json once a vimwiki
+" buffer loads — no explicit nuwiki#lsp#start() needed.
+
+echomsg '[nuwiki-dev] ready (coc.nvim) — wiki root: $WIKI_DIR'
+echomsg '[nuwiki-dev] coc.preferences.jumpCommand = $COC_JUMP'
+echomsg '[nuwiki-dev] <CR> on a [[link]] should open in the CURRENT window'
+echomsg '[nuwiki-dev] :CocList services for status, :messages for log'
+EOF
+}
+
+main() {
+  ensure_node
+  ensure_binary
+  ensure_coc
+  write_coc_settings
+  seed_wiki
+  write_vimrc
+  mkdir -p "$VIM_STATE/swap" "$VIM_STATE/backup" "$VIM_STATE/undo" "$COC_DATA"
+
+  log "launching: vim --clean -u $VIMRC"
+  if [[ $# -gt 0 ]]; then
+    exec vim --clean -u "$VIMRC" "$@"
+  else
+    exec vim --clean -u "$VIMRC" "$WIKI_DIR/index.wiki"
+  fi
+}
+
+main "$@"

development/tests/test-keymaps-vim.vim

@@ -477,6 +477,50 @@ call s:record(
       \ 'ext=' . get(get(s:wl, 1, {}), 'ext', ''))
 unlet g:nuwiki_wikis
 
+" ===== Follow-link resolves + opens in the current window (regression) =====
+" follow_link_or_create() must resolve the definition itself and `:edit` the
+" target in the CURRENT window — including a page that does not exist yet
+" (create-on-follow). We open the URI ourselves rather than delegating to
+" :LspDefinition / coc's jumpDefinition because those fetch the target text
+" (vim-lsp readfile()s it, throwing E484 for a missing page and aborting the
+" jump). This harness loads only nuwiki, so :LspDefinition is absent and the
+" coc branch of s:open_definition() runs once CocAction* are stubbed.
+" The stubbed getDefinition points at a NON-EXISTENT file, so a green result
+" proves both current-window placement and create-on-follow.
+let g:_nuwiki_target = tempname() . '-newpage.wiki'
+function! CocActionAsync(...) abort
+endfunction
+function! CocAction(action, ...) abort
+  if a:action ==# 'definitions'
+    return [{ 'uri': 'file://' . g:_nuwiki_target,
+          \   'range': { 'start': { 'line': 0, 'character': 0 },
+          \              'end':   { 'line': 0, 'character': 0 } } }]
+  endif
+  return []
+endfunction
+" `:edit` must be able to abandon the (modified) scratch buffer.
+let s:had_hidden = &hidden
+set hidden
+let s:seed = expand('%:p')
+call s:set_buf(['[[NewPage]] rest'])
+call cursor(1, 4)
+call nuwiki#commands#follow_link_or_create()
+let s:now = expand('%:p')
+call s:record(
+      \ (s:now =~# 'newpage\.wiki$' && s:now !=# s:seed) ? 1 : 0,
+      \ 'cr.follow_opens_missing_page_in_current_window',
+      \ 'buf=' . s:now)
+let &hidden = s:had_hidden
+delfunction CocAction
+delfunction CocActionAsync
+unlet g:_nuwiki_target
+" NOTE: the vim-lsp branch of s:open_definition() can't be driven headlessly —
+" it gates on `exists('*lsp#send_request')`, which returns 0 for an inline stub
+" (Vim only resolves real autoload files). It shares the same s:open_location()
+" open logic the coc case above exercises, and mirrors the shipped
+" follow_link_drop() request mechanism; its end-to-end coverage is the manual
+" development/start-vim.sh check.
+
 " ===== Wrap up =====
 
 call add(s:results, '')

development/vimwiki-gap.md

@@ -44,29 +44,40 @@ fix site.
 
 ## Regressions (reported by users — verify, then fix)
 
-- [ ] **`<CR>` link-follow opens a new tab instead of reusing the current
-  window** — pressing `<CR>` on a link used to open the target in the *same*
-  tab/window the user was browsing in (upstream behavior). It now opens a
-  **new tab and switches to it**. Reported on Vim 9.x + Dein.
-  _Investigation so far:_ the nuwiki `<CR>` path is **unchanged** by the recent
-  P1 #1/#2/#3 work — `git blame` shows the `<CR>` map (`ftplugin/vimwiki.vim`
-  Vim branch `:206`, Neovim branch `lua/nuwiki/keymaps.lua:161`) and the
-  `follow_link_or_create` → jump-definition chain were not touched; only
-  `<C-S-CR>` was repointed to `follow_link_drop()` in `f65d861`. Both client
-  jump paths open in the current window by default
-  (`vim.lsp.buf.definition()` with no opts; Vim `s:jump_definition()` →
-  `LspDefinition`, `autoload/nuwiki/commands.vim:73`), so the new-tab behavior
-  is **not** coming from nuwiki's own placement logic as written.
-  _Rule out first (env, per memory):_ a **stale dein copy** of the plugin
-  (`bin/nuwiki-ls` + copied ftplugin) and a **double `rtp` entry** where the
-  upstream vimwiki bundle is still loaded alongside nuwiki — either can shadow
-  the `<CR>` map or pull in upstream/`LspDefinition --tab`-style behavior.
-  Recache dein + rebuild + restart LSP and confirm only nuwiki's ftplugin is
-  active before treating this as a nuwiki code bug.
-  _Suspected sites if it reproduces clean:_ vim-lsp's definition-open default
-  (Vim) and the `vim.lsp.buf.definition()` handler (Neovim) — pin which `<CR>`
-  press (bare-word wrap vs. existing-link follow) triggers the tab and whether
-  the server's definition response shape steers placement.
+- [x] **`<CR>` link-follow: wrong window placement + no create-on-follow on the
+  Vim clients** — two related Vim-branch bugs (Neovim path was already correct):
+  (a) on coc.nvim, `<CR>` opened the target in a **new tab** instead of the
+  current window; (b) on **both** vim-lsp and coc, `<CR>` on a link to a
+  not-yet-created page **failed to open/create it**.
+  _Root cause:_ the Vim follow path delegated to the LSP client's jump UI
+  (`:LspDefinition` / `CocActionAsync('jumpDefinition')`). Those fetch the
+  target's text before jumping — vim-lsp `readfile()`s it for the quickfix entry
+  (`autoload/lsp/utils/location.vim`), which throws `E484` for a missing file
+  and aborts the jump (→ no create-on-follow); coc, lacking an explicit open
+  command, fell back to the user's `coc.preferences.jumpCommand` (→ new tab).
+  The server itself was correct throughout — verified over JSON-RPC that
+  `textDocument/definition` returns a *synthesised* location for missing pages
+  and resolves existing links.
+  _Fix:_ stop delegating. `nuwiki#commands#follow_link_or_create()` /
+  `follow_link_drop()` now resolve `textDocument/definition` directly and open
+  the URI ourselves via a shared `s:open_definition(open_cmd)` helper
+  (`autoload/nuwiki/commands.vim`) — `:edit` for `<CR>`, `tab drop` for
+  `<C-S-CR>`. `:edit` opens a buffer for a missing path (save creates it,
+  matching vimwiki) and gives exact current-window placement regardless of the
+  user's coc jumpCommand. Covered by
+  `cr.follow_opens_missing_page_in_current_window` in
+  `development/tests/test-keymaps-vim.vim`; manually reproducible via
+  `development/start-vim.sh` (vim-lsp) and `development/start-vim-coc.sh` (coc).
+- [x] **coc.nvim reported valid links as broken / couldn't resolve** — only via
+  the new `development/start-vim-coc.sh` launcher: its generated
+  `coc-settings.json` registered the server with `command`/`filetypes` but no
+  `initializationOptions`, so `wiki_root` never reached the server and it
+  resolved links against its default (`~/vimwiki`). _Fix:_ the launcher now
+  emits `initializationOptions` **and** `settings.nuwiki` mirroring the vim-lsp
+  client (`autoload/nuwiki/lsp.vim` `s:settings()`). Verified with a headless
+  coc.nvim run: `[[Notes]]` resolves, only genuinely-missing links warn. (Shipped
+  plugin only — no production code change; coc users configure their own
+  `coc-settings.json` per the README snippet.)
 
 ## P2 — Moderate (real users hit these)