fix(vars): E121 in get_wikilocal no-index path; add regression test

s:resolve_index referenced an undefined `a:file` (a copy-paste leftover
from wiki_root_for, whose parameter is named a:file) inside the
buffer-owning-wiki loop. Any get_wikilocal() call with no explicit index
while a wiki buffer was current — i.e. the ftplugin BufRead path — hit
`E121: undefined variable a:file`. The local is `l:file`, and the
surrounding `!empty(l:file)` guard already covers emptiness, so the
clause was both wrong and redundant; removed it.

Add development/tests/test-vars-vim.{sh,vim} covering the shim:
per-wiki-index resolution, global-default fallback, out-of-range clamp,
the no-index owning-wiki path (direct guard for this E121), and the
single-wiki shorthand. Wired into CI. 14/14 pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

development/tests/test-vars-vim.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+#
+# development/tests/test-vars-vim.sh — exercises the vimwiki compatibility
+# shim (autoload/vimwiki/vars.vim) that third-party plugins (vimwiki-sync,
+# vim-zettel) call via vimwiki#vars#get_wikilocal.
+#
+# Runs test-vars-vim.vim under headless Vim; that script writes PASS/FAIL
+# lines to $NUWIKI_VARS_OUT. Covers per-wiki-index resolution, global
+# fallback, out-of-range clamp, the no-index "owning wiki" path (the
+# BufRead path that previously raised E121), and the single-wiki shorthand.
+#
+# Exit code: 0 when every check passes, 1 on any FAIL or missing output.
+# Skips (exit 0) when vim is not installed.
+
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+
+log() { printf '\033[1;34m[vars-vim]\033[0m %s\n' "$*"; }
+
+if ! command -v vim >/dev/null 2>&1; then
+  log 'vim not installed — skipping'
+  exit 0
+fi
+
+TMP="$(mktemp -d -t nuwiki-vars-vim-test-XXXXXX)"
+trap 'rm -rf "$TMP"' EXIT
+
+DIR_A="$TMP/wiki_a"
+DIR_B="$TMP/wiki_b"
+mkdir -p "$DIR_A" "$DIR_B"
+printf '= Home =\n' > "$DIR_A/index.wiki"
+printf '= B =\n'    > "$DIR_B/index.wiki"
+
+OUT="$TMP/vars.out"
+
+VIMRC="$TMP/vimrc"
+cat > "$VIMRC" <<EOF
+set nocompatible
+let &runtimepath = '$REPO_ROOT' . ',' . &runtimepath
+EOF
+
+log 'running Vim vars-shim harness…'
+NUWIKI_VARS_OUT="$OUT" \
+NUWIKI_VARS_DIR_A="$DIR_A" \
+NUWIKI_VARS_DIR_B="$DIR_B" \
+  timeout 30 vim -e -s -u "$VIMRC" \
+    -c "source $REPO_ROOT/development/tests/test-vars-vim.vim" \
+    </dev/null >"$TMP/vim.log" 2>&1 || true
+
+if [[ ! -f "$OUT" ]]; then
+  echo 'vars harness produced no output' >&2
+  echo '--- vim log ---' >&2
+  cat "$TMP/vim.log" >&2 || true
+  exit 1
+fi
+
+cat "$OUT"
+PASSED="$(grep -c '^PASS ' "$OUT" || true)"
+FAILED="$(grep -c '^FAIL ' "$OUT" || true)"
+echo "SUMMARY: ${PASSED} passed, ${FAILED} failed"
+
+if [[ "$FAILED" -ne 0 ]]; then
+  exit 1
+fi
+log 'vars shim OK ✓'
+exit 0

development/tests/test-vars-vim.vim

@@ -0,0 +1,57 @@
+" development/tests/test-vars-vim.vim — exercises the vimwiki compat shim
+" (autoload/vimwiki/vars.vim) that third-party plugins call.
+"
+" Sourced by test-vars-vim.sh under headless Vim. Writes PASS/FAIL lines to
+" $NUWIKI_VARS_OUT; the shell wrapper fails on any FAIL (or missing output).
+
+let s:out = []
+let s:dir_a = $NUWIKI_VARS_DIR_A
+let s:dir_b = $NUWIKI_VARS_DIR_B
+
+function! s:check(desc, got, want) abort
+  if a:got ==# a:want
+    call add(s:out, 'PASS ' . a:desc)
+  else
+    call add(s:out, 'FAIL ' . a:desc . '  got=[' . a:got . '] want=[' . a:want . ']')
+  endif
+endfunction
+
+" ----- multi-wiki: explicit index -----
+let g:nuwiki_wikis = [
+  \ {'root': s:dir_a, 'file_extension': 'wiki', 'syntax': 'markdown'},
+  \ {'root': s:dir_b, 'file_extension': '.wiki'},
+  \ ]
+let g:nuwiki_syntax = 'vimwiki'
+
+call s:check('idx0 path',   vimwiki#vars#get_wikilocal('path', 0),      s:dir_a . '/')
+call s:check('idx0 ext',    vimwiki#vars#get_wikilocal('ext', 0),       '.wiki')
+call s:check('idx0 syntax', vimwiki#vars#get_wikilocal('syntax', 0),    'markdown')
+" wiki[1] doesn't set syntax → global default
+call s:check('idx1 path',   vimwiki#vars#get_wikilocal('path', 1),      s:dir_b . '/')
+call s:check('idx1 syntax', vimwiki#vars#get_wikilocal('syntax', 1),    'vimwiki')
+" out-of-range clamps to first wiki
+call s:check('idx9 clamp',  vimwiki#vars#get_wikilocal('path', 9),      s:dir_a . '/')
+" misc keys
+call s:check('is_temporary', vimwiki#vars#get_wikilocal('is_temporary_wiki', 0) . '', '0')
+call s:check('unknown key',  vimwiki#vars#get_wikilocal('bogus', 0),    '')
+
+" ----- no index: resolve the wiki owning the current buffer -----
+" (this is the BufRead path; regression guard for the s:resolve_index E121.)
+execute 'edit ' . fnameescape(s:dir_b . '/index.wiki')
+call s:check('noarg owning wiki_b', vimwiki#vars#get_wikilocal('path'), s:dir_b . '/')
+execute 'edit ' . fnameescape(s:dir_a . '/index.wiki')
+call s:check('noarg owning wiki_a', vimwiki#vars#get_wikilocal('path'), s:dir_a . '/')
+" buffer outside any wiki → first wiki
+enew
+call s:check('noarg outside→first', vimwiki#vars#get_wikilocal('path'), s:dir_a . '/')
+
+" ----- single-wiki shorthand (no g:nuwiki_wikis) -----
+unlet g:nuwiki_wikis
+let g:nuwiki_wiki_root = s:dir_a
+let g:nuwiki_file_extension = 'txt'
+enew
+call s:check('shorthand path',   vimwiki#vars#get_wikilocal('path'),   s:dir_a . '/')
+call s:check('shorthand ext',    vimwiki#vars#get_wikilocal('ext'),    '.txt')
+call s:check('shorthand syntax', vimwiki#vars#get_wikilocal('syntax'), 'vimwiki')
+
+call writefile(s:out, $NUWIKI_VARS_OUT)