fix: lifecycle cleanup and defensive runtime checks (#29)

* fix(commands): register VimLeavePre to call stop_all

Problem: spawned compiler processes and watching autocmds were never
cleaned up when Neovim exited, leaving orphaned processes running.

Solution: register a VimLeavePre autocmd in commands setup that calls
compiler.stop_all(), which kills active processes, unwatches all
buffers, and stops the reload server.

* fix(compiler): replace BufWipeout with BufUnload

Problem: cleanup autocmds used BufWipeout, which only fires for
:bwipeout. The common :bdelete path (used by most buffer managers
and nvim_buf_delete) fires BufUnload but not BufWipeout, so processes
and watches leaked on normal buffer deletion.

Solution: switch all three cleanup autocmds from BufWipeout to
BufUnload, which fires for both :bdelete and :bwipeout.

* fix(init): guard against unnamed buffer in public API

Problem: calling compile/toggle/clean/open on an unsaved scratch
buffer passed an empty string as ctx.file, producing nonsensical
output paths like ".pdf" and silently passing empty strings to
compiler binaries.

Solution: add an early return with a WARN notification in compile,
toggle, clean, and open when the buffer has no file name.

* fix(compiler): add fs_stat check to one-shot open path

Problem: the long-running process path already guarded opens with
vim.uv.fs_stat(), but the one-shot compile path and M.open() did not.
Compilation can exit 0 and produce no output, and output files can be
externally deleted between compile and open.

Solution: add the same fs_stat guard to the one-shot open branch and
to M.open() before attempting to launch the viewer.

* fix(compiler): check executable before spawning process

Problem: if a configured binary was missing or not in PATH, vim.system
would fail silently or with a cryptic OS error. The user had no
actionable feedback without running :checkhealth.

Solution: check vim.fn.executable() at the start of M.compile() and
notify with an ERROR-level message pointing to :checkhealth preview
if the binary is not found.

* fix(compiler): reformat one-shot open condition for line length

Problem: the added fs_stat condition exceeded stylua's line length
limit on the one-shot open guard.

Solution: split the boolean condition across multiple lines to match
the project's stylua formatting rules.

lua/preview/commands.lua

@@ -57,6 +57,12 @@ function M.setup()
     end,
     desc = 'Toggle, compile, clean, open, or check status of document preview',
   })
+
+  vim.api.nvim_create_autocmd('VimLeavePre', {
+    callback = function()
+      require('preview.compiler').stop_all()
+    end,
+  })
 end
 
 return M

lua/preview/compiler.lua

@@ -58,6 +58,14 @@ end
 function M.compile(bufnr, name, provider, ctx, opts)
   opts = opts or {}
 
+  if vim.fn.executable(provider.cmd[1]) ~= 1 then
+    vim.notify(
+      '[preview.nvim]: "' .. provider.cmd[1] .. '" is not executable (run :checkhealth preview)',
+      vim.log.levels.ERROR
+    )
+    return
+  end
+
   if vim.bo[bufnr].modified then
     vim.cmd('silent! update')
   end
@@ -170,7 +178,7 @@ function M.compile(bufnr, name, provider, ctx, opts)
 
     active[bufnr] = { obj = obj, provider = name, output_file = output_file, is_reload = true }
 
-    vim.api.nvim_create_autocmd('BufWipeout', {
+    vim.api.nvim_create_autocmd('BufUnload', {
       buffer = bufnr,
       once = true,
       callback = function()
@@ -230,7 +238,12 @@ function M.compile(bufnr, name, provider, ctx, opts)
           r.inject(output_file)
           r.broadcast()
         end
-        if provider.open and not opened[bufnr] and output_file ~= '' then
+        if
+          provider.open
+          and not opened[bufnr]
+          and output_file ~= ''
+          and vim.uv.fs_stat(output_file)
+        then
           if provider.open == true then
             vim.ui.open(output_file)
           elseif type(provider.open) == 'table' then
@@ -279,7 +292,7 @@ function M.compile(bufnr, name, provider, ctx, opts)
 
   active[bufnr] = { obj = obj, provider = name, output_file = output_file }
 
-  vim.api.nvim_create_autocmd('BufWipeout', {
+  vim.api.nvim_create_autocmd('BufUnload', {
     buffer = bufnr,
     once = true,
     callback = function()
@@ -374,7 +387,7 @@ function M.toggle(bufnr, name, provider, ctx_builder)
   log.dbg('watching buffer %d with provider "%s"', bufnr, name)
   vim.notify('[preview.nvim]: watching with "' .. name .. '"', vim.log.levels.INFO)
 
-  vim.api.nvim_create_autocmd('BufWipeout', {
+  vim.api.nvim_create_autocmd('BufUnload', {
     buffer = bufnr,
     once = true,
     callback = function()
@@ -452,6 +465,10 @@ function M.open(bufnr, open_config)
     log.dbg('no last output file for buffer %d', bufnr)
     return false
   end
+  if not vim.uv.fs_stat(output) then
+    log.dbg('output file no longer exists for buffer %d: %s', bufnr, output)
+    return false
+  end
   if type(open_config) == 'table' then
     local open_cmd = vim.list_extend({}, open_config)
     table.insert(open_cmd, output)

lua/preview/init.lua

@@ -146,6 +146,10 @@ end
 ---@param bufnr? integer
 function M.compile(bufnr)
   bufnr = bufnr or vim.api.nvim_get_current_buf()
+  if vim.api.nvim_buf_get_name(bufnr) == '' then
+    vim.notify('[preview.nvim]: buffer has no file name', vim.log.levels.WARN)
+    return
+  end
   local name = M.resolve_provider(bufnr)
   if not name then
     vim.notify('[preview.nvim]: no provider configured for this filetype', vim.log.levels.WARN)
@@ -165,6 +169,10 @@ end
 ---@param bufnr? integer
 function M.clean(bufnr)
   bufnr = bufnr or vim.api.nvim_get_current_buf()
+  if vim.api.nvim_buf_get_name(bufnr) == '' then
+    vim.notify('[preview.nvim]: buffer has no file name', vim.log.levels.WARN)
+    return
+  end
   local name = M.resolve_provider(bufnr)
   if not name then
     vim.notify('[preview.nvim]: no provider configured for this filetype', vim.log.levels.WARN)
@@ -178,6 +186,10 @@ end
 ---@param bufnr? integer
 function M.toggle(bufnr)
   bufnr = bufnr or vim.api.nvim_get_current_buf()
+  if vim.api.nvim_buf_get_name(bufnr) == '' then
+    vim.notify('[preview.nvim]: buffer has no file name', vim.log.levels.WARN)
+    return
+  end
   local name = M.resolve_provider(bufnr)
   if not name then
     vim.notify('[preview.nvim]: no provider configured for this filetype', vim.log.levels.WARN)
@@ -190,6 +202,10 @@ end
 ---@param bufnr? integer
 function M.open(bufnr)
   bufnr = bufnr or vim.api.nvim_get_current_buf()
+  if vim.api.nvim_buf_get_name(bufnr) == '' then
+    vim.notify('[preview.nvim]: buffer has no file name', vim.log.levels.WARN)
+    return
+  end
   local name = M.resolve_provider(bufnr)
   local open_config = name and config.providers[name] and config.providers[name].open
   if not compiler.open(bufnr, open_config) then

spec/commands_spec.lua

@@ -11,6 +11,19 @@ describe('commands', function()
       local cmds = vim.api.nvim_get_commands({})
       assert.is_not_nil(cmds.Preview)
     end)
+
+    it('registers VimLeavePre autocmd', function()
+      require('preview.commands').setup()
+      local aus = vim.api.nvim_get_autocmds({ event = 'VimLeavePre' })
+      local found = false
+      for _, au in ipairs(aus) do
+        if au.callback then
+          found = true
+          break
+        end
+      end
+      assert.is_true(found)
+    end)
   end)
 
   describe('dispatch', function()

spec/compiler_spec.lua

@@ -99,6 +99,35 @@ describe('compiler', function()
       helpers.delete_buffer(bufnr)
     end)
 
+    it('notifies and returns when binary is not executable', function()
+      local bufnr = helpers.create_buffer({ 'hello' }, 'text')
+      vim.api.nvim_buf_set_name(bufnr, '/tmp/preview_test_nobin.txt')
+      vim.bo[bufnr].modified = false
+
+      local notified = false
+      local orig = vim.notify
+      vim.notify = function(msg)
+        if msg:find('not executable') then
+          notified = true
+        end
+      end
+
+      local provider = { cmd = { 'totally_nonexistent_binary_xyz_preview' } }
+      local ctx = {
+        bufnr = bufnr,
+        file = '/tmp/preview_test_nobin.txt',
+        root = '/tmp',
+        ft = 'text',
+      }
+
+      compiler.compile(bufnr, 'nobin', provider, ctx)
+      vim.notify = orig
+
+      assert.is_true(notified)
+      assert.is_nil(compiler._test.active[bufnr])
+      helpers.delete_buffer(bufnr)
+    end)
+
     it('fires PreviewCompileFailed on non-zero exit', function()
       local bufnr = helpers.create_buffer({ 'hello' }, 'text')
       vim.api.nvim_buf_set_name(bufnr, '/tmp/preview_test_fail.txt')

spec/init_spec.lua

@@ -108,4 +108,62 @@ describe('preview', function()
       helpers.delete_buffer(bufnr)
     end)
   end)
+
+  describe('unnamed buffer guard', function()
+    before_each(function()
+      helpers.reset_config({ typst = true })
+      preview = require('preview')
+    end)
+
+    local function capture_notify(fn)
+      local msg = nil
+      local orig = vim.notify
+      vim.notify = function(m)
+        msg = m
+      end
+      fn()
+      vim.notify = orig
+      return msg
+    end
+
+    it('compile warns on unnamed buffer', function()
+      local bufnr = helpers.create_buffer({}, 'typst')
+      local msg = capture_notify(function()
+        preview.compile(bufnr)
+      end)
+      assert.is_not_nil(msg)
+      assert.is_truthy(msg:find('no file name'))
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('toggle warns on unnamed buffer', function()
+      local bufnr = helpers.create_buffer({}, 'typst')
+      local msg = capture_notify(function()
+        preview.toggle(bufnr)
+      end)
+      assert.is_not_nil(msg)
+      assert.is_truthy(msg:find('no file name'))
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('clean warns on unnamed buffer', function()
+      local bufnr = helpers.create_buffer({}, 'typst')
+      local msg = capture_notify(function()
+        preview.clean(bufnr)
+      end)
+      assert.is_not_nil(msg)
+      assert.is_truthy(msg:find('no file name'))
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('open warns on unnamed buffer', function()
+      local bufnr = helpers.create_buffer({}, 'typst')
+      local msg = capture_notify(function()
+        preview.open(bufnr)
+      end)
+      assert.is_not_nil(msg)
+      assert.is_truthy(msg:find('no file name'))
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
 end)