fix(startup): server fails if $NVIM_APPNAME is relative dir #30310

Problem:
If $NVIM_APPNAME is a relative dir path, Nvim fails to start its
primary/default server, and `v:servername` is empty.
Root cause is d34c64e342dfba9248d1055e702d02620a1b31a8, but this wasn't
noticed until 96128a5076b7 started reporting the error more loudly.

Solution:
- `server_address_new`: replace slashes "/" in the appname before using
  it as a servername.
- `vim_mktempdir`: always prefer the system-wide top-level "nvim.user/"
  directory. That isn't intended to be specific to NVIM_APPNAME; rather,
  each *subdirectory* ("nvim.user/xxx") is owned by each Nvim instance.
  Nvim "apps" can be identified by the server socket(s) stored in those
  per-Nvim subdirs.

fix #30256

1 files changed, 2 insertions, 13 deletions

diff --git a/test/functional/core/fileio_spec.lua b/test/functional/core/fileio_spec.lua
index 073041fced..d33710a63d 100644
--- a/test/functional/core/fileio_spec.lua
+++ b/test/functional/core/fileio_spec.lua
@@ -321,11 +321,11 @@ end)
 describe('tmpdir', function()
   local tmproot_pat = [=[.*[/\\]nvim%.[^/\\]+]=]
   local testlog = 'Xtest_tmpdir_log'
-  local os_tmpdir
+  local os_tmpdir ---@type string
 
   before_each(function()
     -- Fake /tmp dir so that we can mess it up.
-    os_tmpdir = vim.uv.fs_mkdtemp(vim.fs.dirname(t.tmpname(false)) .. '/nvim_XXXXXXXXXX')
+    os_tmpdir = assert(vim.uv.fs_mkdtemp(vim.fs.dirname(t.tmpname(false)) .. '/nvim_XXXXXXXXXX'))
   end)
 
   after_each(function()
@@ -414,15 +414,4 @@ describe('tmpdir', function()
     rm_tmpdir()
     eq('E5431: tempdir disappeared (3 times)', api.nvim_get_vvar('errmsg'))
   end)
-
-  it('$NVIM_APPNAME relative path', function()
-    clear({
-      env = {
-        NVIM_APPNAME = 'a/b',
-        NVIM_LOG_FILE = testlog,
-        TMPDIR = os_tmpdir,
-      },
-    })
-    matches([=[.*[/\\]a%%b%.[^/\\]+]=], fn.tempname())
-  end)
 end)