feat(server): instance "name", store pipes in stdpath(state)

Problem:
- Unix sockets are created in random /tmp dirs.
  - /tmp is messy, unclear when OSes actually clear it.
  - The generated paths are very ugly. This adds friction to reasoning
    about which paths belong to which Nvim instances.
- No way to provide a human-friendly way to identify Nvim instances in
  logs or server addresses.

Solution:
- Store unix sockets in stdpath('state')
- Allow --listen "name" and serverstart("name") to given a name (which
  is appended to a generated path).

TODO:
- is stdpath(state) the right place?

5 files changed, 57 insertions, 41 deletions

diff --git a/test/README.md b/test/README.md
index a6ce3c6d28..a67040e68c 100644
--- a/test/README.md
+++ b/test/README.md
@@ -91,25 +91,33 @@ or:
 Debugging tests
 ---------------
 
+- Each test gets a test id which looks like "T123". This also appears in the
+  log file. Child processes spawned from a test appear in the logs with the
+  *parent* name followed by "/c". Example:
+  ```
+    DBG 2022-06-15T18:37:45.226 T57.58016.0   UI: flush
+    DBG 2022-06-15T18:37:45.226 T57.58016.0   inbuf_poll:442: blocking... events_enabled=0 events_pending=0
+    DBG 2022-06-15T18:37:45.227 T57.58016.0/c UI: stop
+    INF 2022-06-15T18:37:45.227 T57.58016.0/c os_exit:595: Nvim exit: 0
+    DBG 2022-06-15T18:37:45.229 T57.58016.0   read_cb:118: closing Stream (0x7fd5d700ea18): EOF (end of file)
+    INF 2022-06-15T18:37:45.229 T57.58016.0   on_process_exit:400: exited: pid=58017 status=0 stoptime=0
+  ```
 - You can set `$GDB` to [run tests under gdbserver](https://github.com/neovim/neovim/pull/1527).
   And if `$VALGRIND` is set it will pass `--vgdb=yes` to valgrind instead of
   starting gdbserver directly.
-- Hanging tests often happen due to unexpected `:h press-enter` prompts. The
+- Hanging tests can happen due to unexpected "press-enter" prompts. The
   default screen width is 50 columns. Commands that try to print lines longer
   than 50 columns in the command-line, e.g. `:edit very...long...path`, will
-  trigger the prompt. In this case, a shorter path or `:silent edit` should be
-  used.
+  trigger the prompt. Try using a shorter path, or `:silent edit`.
 - If you can't figure out what is going on, try to visualize the screen. Put
   this at the beginning of your test:
-
-    ```lua
-    local Screen = require('test.functional.ui.screen')
-    local screen = Screen.new()
-    screen:attach()
-    ```
-
-  Afterwards, put `screen:snapshot_util()` at any position in your test. See the
-  comment at the top of `test/functional/ui/screen.lua` for more.
+  ```lua
+  local Screen = require('test.functional.ui.screen')
+  local screen = Screen.new()
+  screen:attach()
+  ```
+  Then put `screen:snapshot_util()` anywhere in your test. See the comments in
+  `test/functional/ui/screen.lua` for more info.
 
 Filtering Tests
 ---------------
@@ -276,9 +284,6 @@ Number; !must be defined to function properly):
 
 - `NVIM_PRG` (F) (S): path to Nvim executable (default: `build/bin/nvim`).
 
-- `NVIM_TEST` (F) (S): Test id (example: "T1000") generated by the test runner
-  and prepended to `$NVIM_LOG_FILE` messages.
-
 - `NVIM_TEST_MAIN_CDEFS` (U) (1): makes `ffi.cdef` run in main process. This
   raises a possibility of bugs due to conflicts in header definitions, despite
   the counters, but greatly speeds up unit tests by not requiring `ffi.cdef` to
diff --git a/test/functional/core/log_spec.lua b/test/functional/core/log_spec.lua
index 8553197305..3b1ccd9559 100644
--- a/test/functional/core/log_spec.lua
+++ b/test/functional/core/log_spec.lua
@@ -1,18 +1,19 @@
 local helpers = require('test.functional.helpers')(after_each)
 local assert_log = helpers.assert_log
 local clear = helpers.clear
+local command = helpers.command
 local eq = helpers.eq
 local exec_lua = helpers.exec_lua
+local expect_exit = helpers.expect_exit
 local request = helpers.request
 local retry = helpers.retry
-local expect_exit = helpers.expect_exit
 
 describe('log', function()
-  local test_log_file = 'Xtest_logging'
+  local testlog = 'Xtest_logging'
 
   after_each(function()
-    expect_exit('qa!')
-    os.remove(test_log_file)
+    expect_exit(command, 'qa!')
+    os.remove(testlog)
   end)
 
   it('skipped before log_init', function()
@@ -33,13 +34,14 @@ describe('log', function()
     --    ERR 2022-05-29T12:30:03.814 T2/child   log_init:110: test log message
 
     clear({env={
-      NVIM_LOG_FILE=test_log_file,
-      -- TODO: Can remove this after nvim_log #7062 is merged.
+      NVIM_LOG_FILE=testlog,
+      -- TODO: remove this after nvim_log #7062 is merged.
       __NVIM_TEST_LOG='1'
       }})
 
-    retry(nil, nil, function()
-      assert_log('T%d+\\.%d+\\.\\d +log_init:%d+: test log message', test_log_file, 100)
+    local tid = _G._nvim_test_id
+    retry(nil, 1000, function()
+      assert_log(tid..'%.%d+%.%d +server_init:%d+: test log message', testlog, 100)
     end)
 
     exec_lua([[
@@ -47,9 +49,9 @@ describe('log', function()
       vim.fn.jobwait({ j1 }, 10000)
     ]])
 
-    -- Child Nvim spawned by jobstart() appends "/child" to parent name.
-    retry(nil, nil, function()
-      assert_log('T%d+/child +log_init:%d+: test log message', test_log_file, 100)
+    -- Child Nvim spawned by jobstart() appends "/c" to parent name.
+    retry(nil, 1000, function()
+      assert_log('%.%d+%.%d/c +server_init:%d+: test log message', testlog, 100)
     end)
   end)
 end)
diff --git a/test/functional/helpers.lua b/test/functional/helpers.lua
index 0122229e77..d31d337b63 100644
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -431,16 +431,20 @@ end
 function module.new_argv(...)
   local args = {unpack(module.nvim_argv)}
   table.insert(args, '--headless')
+  if _G._nvim_test_id then
+    -- Set the server name to the test-id for logging. #8519
+    table.insert(args, '--listen')
+    table.insert(args, _G._nvim_test_id)
+  end
   local new_args
   local io_extra
-  local env = {}
+  local env = nil
   local opts = select(1, ...)
   if type(opts) ~= 'table' then
     new_args = {...}
   else
     args = remove_args(args, opts.args_rm)
     if opts.env then
-      opts.env['NVIM_TEST'] = nil
       local env_opt = {}
       for k, v in pairs(opts.env) do
         assert(type(k) == 'string')
@@ -461,11 +465,12 @@ function module.new_argv(...)
         'TMPDIR',
         'VIMRUNTIME',
       }) do
-        -- Set these from the environment only if not in opts.env.
+        -- Set these from the environment unless the caller defined them.
         if not env_opt[k] then
           env_opt[k] = os.getenv(k)
         end
       end
+      env = {}
       for k, v in pairs(env_opt) do
         env[#env + 1] = k .. '=' .. v
       end
@@ -476,10 +481,6 @@ function module.new_argv(...)
   for _, arg in ipairs(new_args) do
     table.insert(args, arg)
   end
-
-  -- TODO(justinmk): introduce v:name and use that instead.
-  table.insert(env, ('NVIM_TEST=%s'):format(_G._nvim_test_id or '?'))
-
   return args, env, io_extra
 end
 
diff --git a/test/functional/terminal/api_spec.lua b/test/functional/terminal/api_spec.lua
index e28cc03597..b3a0b8a2c8 100644
--- a/test/functional/terminal/api_spec.lua
+++ b/test/functional/terminal/api_spec.lua
@@ -6,7 +6,7 @@ if helpers.pending_win32(pending) then return end
 
 describe('api', function()
   local screen
-  local socket_name = "Xtest_functional_api.sock"
+  local socket_name = "./Xtest_functional_api.sock"
 
   before_each(function()
     helpers.clear()
@@ -29,7 +29,7 @@ describe('api', function()
       {4:~                                                 }|
       {4:~                                                 }|
       {4:~                                                 }|
-      ]]..socket_name..[[                         |
+      ]]..socket_name..[[                       |
       {3:-- TERMINAL --}                                    |
     ]])
 
diff --git a/test/functional/vimscript/server_spec.lua b/test/functional/vimscript/server_spec.lua
index de64a77b4d..ea07be231d 100644
--- a/test/functional/vimscript/server_spec.lua
+++ b/test/functional/vimscript/server_spec.lua
@@ -30,7 +30,7 @@ describe('server', function()
     eq('', eval('$NVIM_LISTEN_ADDRESS'))
     local servers = funcs.serverlist()
     eq(1, #servers)
-    ok(string.len(servers[1]) > 4)  -- Like /tmp/nvim…/… or \\.\pipe\…
+    ok(string.len(servers[1]) > 4)  -- "~/.local/state/nvim…/…" or "\\.\pipe\…"
   end)
 
   it('sets v:servername at startup or if all servers were stopped', function()
@@ -54,7 +54,7 @@ describe('server', function()
 
     -- v:servername and $NVIM take the next available server.
     local servername = (iswin() and [[\\.\pipe\Xtest-functional-server-pipe]]
-                                or 'Xtest-functional-server-socket')
+                                or './Xtest-functional-server-socket')
     funcs.serverstart(servername)
     eq(servername, meths.get_vvar('servername'))
     -- Not set in the current process, only in children.
@@ -66,7 +66,7 @@ describe('server', function()
     eq(0, eval("serverstop('bogus-socket-name')"))
   end)
 
-  it('parses endpoints correctly', function()
+  it('parses endpoints', function()
     clear_serverlist()
     eq({}, funcs.serverlist())
 
@@ -101,6 +101,10 @@ describe('server', function()
     eq(expected, funcs.serverlist())
     clear_serverlist()
 
+    -- Address without slashes is a "name" which is appended to a generated path. #8519
+    matches([[.*[/\\]xtest1%.2%.3%.4[^/\\]*]], funcs.serverstart('xtest1.2.3.4'))
+    clear_serverlist()
+
     eq('Vim:Failed to start server: invalid argument',
       pcall_err(funcs.serverstart, '127.0.0.1:65536'))  -- invalid port
     eq({}, funcs.serverlist())
@@ -113,7 +117,7 @@ describe('server', function()
     -- Add some servers.
     local servs = (iswin()
       and { [[\\.\pipe\Xtest-pipe0934]], [[\\.\pipe\Xtest-pipe4324]] }
-      or  { [[Xtest-pipe0934]], [[Xtest-pipe4324]] })
+      or  { [[./Xtest-pipe0934]], [[./Xtest-pipe4324]] })
     for _, s in ipairs(servs) do
       eq(s, eval("serverstart('"..s.."')"))
     end
@@ -146,9 +150,13 @@ describe('startup --listen', function()
 
   it('sets v:servername, overrides $NVIM_LISTEN_ADDRESS', function()
     local addr = (iswin() and [[\\.\pipe\Xtest-listen-pipe]]
-                          or 'Xtest-listen-pipe')
-    clear({ env={ NVIM_LISTEN_ADDRESS='Xtest-env-pipe' },
+                          or './Xtest-listen-pipe')
+    clear({ env={ NVIM_LISTEN_ADDRESS='./Xtest-env-pipe' },
             args={ '--listen', addr } })
     eq(addr, meths.get_vvar('servername'))
+
+    -- Address without slashes is a "name" which is appended to a generated path. #8519
+    clear({ args={ '--listen', 'test-name' } })
+    matches([[.*[/\\]test%-name[^/\\]*]], meths.get_vvar('servername'))
   end)
 end)