feat(server): auto-find port on Windows with async

lua/opencode/cli/server.lua

@@ -1,140 +1,194 @@
+local IS_WINDOWS = vim.fn.has("win32") == 1
+
 local M = {}
 
----@param command string
----@return string
-local function exec(command)
-  -- TODO: Use vim.fn.jobstart for async, and so I can capture stderr (to throw error instead of it writing to the buffer).
-  -- (or even the newer `vim.system`? Could update client.lua too? Or maybe not because SSE is long-running.)
-  local executable = vim.split(command, " ")[1]
-  if vim.fn.executable(executable) == 0 then
-    error("`" .. executable .. "` command is not available", 0)
+---@param command string|string[]
+---@param cb fun(string?)
+local function exec_async(command, cb)
+  if type(command) == "string" then
+    command = vim.split(command, " ")
   end
 
-  local handle = io.popen(command)
-  if not handle then
-    error("Couldn't execute command: " .. command, 0)
+  local executable = command[1]
+  if vim.fn.executable(executable) == 0 then
+    error("`" .. executable .. "` command is not available", 0)
   end
 
-  local output = handle:read("*a")
-  handle:close()
-  return output
+  vim.system(command, { text = true }, function(handle)
+    if handle.code ~= 0 then
+      error("Couldn't execute command: " .. table.concat(command, " "))
+      cb(nil)
+      return
+    end
+    cb(handle.stdout)
+  end)
 end
 
----@return Server[]
-local function find_servers()
+---@class Server
+---@field pid number
+---@field port number
+---@field cwd string
+
+---@param cb fun(servers: Server[])
+local function find_servers(cb)
+  if IS_WINDOWS then
+    exec_async({
+      "powershell",
+      "-NoProfile",
+      "-Command",
+      [[Get-NetTCPConnection -State Listen | ForEach-Object {
+      $p=Get-Process -Id $_.OwningProcess -ea 0;
+      if($p -and ($p.ProcessName -ieq 'opencode' -or $p.ProcessName -ieq 'opencode.exe')) {
+        '{0} {1}' -f $_.OwningProcess, $_.LocalPort
+      }
+    }]],
+    }, function(output)
+      local servers = {}
+      for line in output:gmatch("[^\r\n]+") do
+        local parts = vim.split(line, "%s+")
+        local pid = tonumber(parts[1])
+        local port = tonumber(parts[2])
+
+        if not pid or not port then
+          error("Couldn't parse `opencode` PID and port from entry: " .. line, 0)
+        end
+
+        -- have to skip CWD on Windows as it's non-trivial to get
+        servers[#servers + 1] = {
+          pid = pid,
+          port = port,
+          -- cwd = vim.fn.getcwd(),
+        }
+      end
+      cb(servers)
+    end)
+    return
+  end
+
   if vim.fn.executable("lsof") == 0 then
     -- lsof is a common utility to list open files and ports, but not always available by default.
     error(
       "`lsof` executable not found in `PATH` to auto-find `opencode` — please install it or set `vim.g.opencode_opts.port`",
       0
     )
   end
-  -- Going straight to `lsof` relieves us of parsing `ps` and all the non-portable 'opencode'-containing processes it might return.
-  -- With these flags, we'll only get processes that are listening on TCP ports and have 'opencode' in their command name.
-  -- i.e. pretty much guaranteed to be just opencode server processes.
-  -- `-w` flag suppresses warnings about inaccessible filesystems (e.g. Docker FUSE).
-  local output = exec("lsof -w -iTCP -sTCP:LISTEN -P -n | grep opencode")
-  if output == "" then
-    error("Couldn't find any `opencode` processes", 0)
-  end
 
-  local servers = {}
-  for line in output:gmatch("[^\r\n]+") do
-    -- lsof output: COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
-    local parts = vim.split(line, "%s+")
+  exec_async("lsof -w -iTCP -sTCP:LISTEN -P -n | grep opencode", function(output)
+    if output == "" then
+      error("Couldn't find any `opencode` processes", 0)
+    end
+
+    local servers = {}
+    local pending_cwds = 0
+    local lines = {}
 
-    local pid = tonumber(parts[2])
-    local port = tonumber(parts[9]:match(":(%d+)$")) -- Extract port from NAME field (which is e.g. "127.0.0.1:12345")
-    if not pid or not port then
-      error("Couldn't parse `opencode` PID and port from `lsof` entry: " .. line, 0)
+    -- Collect all lines first
+    for line in output:gmatch("[^\r\n]+") do
+      table.insert(lines, line)
     end
 
-    local cwd = exec("lsof -w -a -p " .. pid .. " -d cwd"):match("%s+(/.*)$")
-    if not cwd then
-      error("Couldn't determine CWD for PID: " .. pid, 0)
+    if #lines == 0 then
+      cb(servers)
+      return
     end
 
-    table.insert(
-      servers,
-      ---@class Server
-      ---@field pid number
-      ---@field port number
-      ---@field cwd string
-      {
-        pid = pid,
-        port = port,
-        cwd = cwd,
-      }
-    )
-  end
-  return servers
+    pending_cwds = #lines
+
+    for _, line in ipairs(lines) do
+      -- lsof output: COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
+      local parts = vim.split(line, "%s+")
+
+      local pid = tonumber(parts[2])
+      local port = tonumber(parts[9]:match(":(%d+)$")) -- Extract port from NAME field (which is e.g. "127.0.0.1:12345")
+      if not pid or not port then
+        error("Couldn't parse `opencode` PID and port from `lsof` entry: " .. line, 0)
+      end
+
+      exec_async("lsof -w -a -p " .. pid .. " -d cwd", function(cwd_result)
+        local cwd = cwd_result:match("%s+(/.*)$")
+
+        if not cwd then
+          error("Couldn't determine CWD for PID: " .. pid, 0)
+        else
+          servers[#servers + 1] = {
+            pid = pid,
+            port = port,
+            cwd = cwd,
+          }
+        end
+
+        pending_cwds = pending_cwds - 1
+        if pending_cwds == 0 then
+          cb(servers)
+        end
+      end)
+    end
+  end)
 end
 
-local function is_descendant_of_neovim(pid)
+---@param cb fun(result: boolean)
+local function is_descendant_of_neovim(pid, cb)
   local neovim_pid = vim.fn.getpid()
   local current_pid = pid
+  local cmd = vim.fn.has("win32") and "wmic process where ProcessId=%d get ParentProcessId /value"
+    or "ps -o ppid= -p %d"
 
   -- Walk up because the way some shells launch processes,
   -- Neovim will not be the direct parent.
-  for _ = 1, 10 do -- limit to 10 steps to avoid infinite loop
-    local parent_pid = tonumber(exec("ps -o ppid= -p " .. current_pid))
-    if not parent_pid then
-      error("Couldn't determine parent PID for: " .. current_pid, 0)
-    end
-
-    if parent_pid == 1 then
-      return false
-    elseif parent_pid == neovim_pid then
-      return true
-    end
+  local steps = {}
 
-    current_pid = parent_pid
+  for _ = 1, 4 do -- limit to 4 steps to avoid infinite loop
+    table.insert(steps, function(next)
+      exec_async(cmd:format(current_pid), function(output)
+        local parent_pid = tonumber(output:match("(%d+)"))
+        if not parent_pid or parent_pid == 1 then
+          cb(false)
+        elseif parent_pid == neovim_pid then
+          cb(true)
+        else
+          current_pid = parent_pid
+          next()
+        end
+      end)
+    end)
   end
 
-  return false
+  table.insert(steps, function()
+    cb(false)
+  end)
+
+  require("opencode.util").chain(steps)
 end
 
----@return Server
-local function find_server_inside_nvim_cwd()
+---@param cb fun(server: Server|nil)
+local function find_server_inside_nvim_cwd(cb)
   local found_server
   local nvim_cwd = vim.fn.getcwd()
-  for _, server in ipairs(find_servers()) do
-    -- CWDs match exactly, or opencode's CWD is under neovim's CWD.
-    if server.cwd:find(nvim_cwd, 1, true) == 1 then
-      found_server = server
-      if is_descendant_of_neovim(server.pid) then
-        -- Stop searching to prioritize embedded
-        break
-      end
-    end
-  end
-
-  if not found_server then
-    error("Couldn't find an `opencode` process running inside Neovim's CWD", 0)
-  end
 
-  return found_server
-end
+  find_servers(function(servers)
+    local steps = {}
 
----@param fn fun(): number Function that checks for the port.
----@param callback fun(ok: boolean, result: any) Called with eventually found port or error if not found after some time.
-local function poll_for_port(fn, callback)
-  local retries = 0
-  local timer = vim.uv.new_timer()
-  timer:start(
-    100,
-    100,
-    vim.schedule_wrap(function()
-      local ok, find_port_result = pcall(fn)
-      if ok or retries >= 20 then
-        timer:stop()
-        timer:close()
-        callback(ok, find_port_result)
-      else
-        retries = retries + 1
+    for i, server in ipairs(servers) do
+      -- CWDs match exactly, or opencode's CWD is under neovim's CWD.
+      if IS_WINDOWS or server.cwd:find(nvim_cwd, 1, true) == 1 then
+        table.insert(steps, function(next)
+          is_descendant_of_neovim(server.pid, function(is_descendant)
+            if is_descendant then
+              found_server = server
+            else
+              next()
+            end
+          end)
+        end)
       end
+    end
+
+    table.insert(steps, function()
+      cb(found_server)
     end)
-  )
+
+    require("opencode.util").chain(steps)
+  end)
 end
 
 ---Test if a process is responding on `port`.
@@ -151,41 +205,64 @@ local function test_port(port)
   end
 end
 
+local PORT_RANGE = { 4096, 5096 }
+---@return number
+local function find_free_port()
+  for port = PORT_RANGE[1], PORT_RANGE[2] do
+    local ok = pcall(test_port, port)
+    if not ok then
+      return port
+    end
+  end
+  error("Couldn't find a free port in range: " .. PORT_RANGE[1] .. "-" .. PORT_RANGE[2], 0)
+end
+
 ---Attempt to get the `opencode` server's port. Tries, in order:
 ---1. A process responding on `opts.port`.
 ---2. Any `opencode` process running inside Neovim's CWD. Prioritizes embedded.
----3. Calling `opts.on_opencode_not_found` and polling for the port.
+---3. Calling `opts.on_opencode_not_found` with random free port in range.
 ---@param callback fun(ok: boolean, result: any) Called with eventually found port or error if not found after some time.
 function M.get_port(callback)
-  local configured_port = require("opencode.config").opts.port
-  local find_port_fn = configured_port and function()
-    return test_port(configured_port)
-  end or function()
-    return find_server_inside_nvim_cwd().port
-  end
-
-  require("opencode.util").chain({
+  local step = {
     function(next)
-      local ok, result = pcall(find_port_fn)
-      if ok then
-        callback(true, result)
-      else
-        next()
-      end
+      local configured_port = require("opencode.config").opts.port
+      vim.schedule(function()
+        if configured_port and test_port(configured_port) then
+          callback(true, configured_port)
+        else
+          next()
+        end
+      end)
     end,
     function(next)
-      local ok, result = pcall(require("opencode.config").opts.on_opencode_not_found)
-      if not ok then
-        callback(false, "Error in `vim.g.opencode_opts.on_opencode_not_found`: " .. result)
-      else
-        -- Always proceed - even if `opencode` wasn't started, failing to find it will give a more helpful error message.
-        next()
-      end
+      find_server_inside_nvim_cwd(function(server)
+        if server then
+          vim.schedule(function()
+            callback(true, server.port)
+          end)
+        else
+          next()
+        end
+      end)
     end,
-    function(_)
-      poll_for_port(find_port_fn, callback)
+    function()
+      vim.schedule(function()
+        local port_ok, port_result = pcall(find_free_port)
+        if not port_ok then
+          callback(false, "Error finding free port: " .. port_result)
+          return
+        end
+        local ok, result = pcall(require("opencode.config").opts.on_opencode_not_found, port_result)
+        if not ok then
+          callback(false, "Error in `vim.g.opencode_opts.on_opencode_not_found`: " .. result)
+        else
+          callback(true, port_result)
+        end
+      end)
     end,
-  })
+  }
+
+  require("opencode.util").chain(step)
 end
 
 return M