test: simplify platform detection (#21020)

Extend the capabilities of is_os to detect more platforms such as
freebsd and openbsd. Also remove `iswin()` helper function as it can be
replaced by `is_os("win")`.

test/functional/lua/fs_spec.lua

@@ -7,10 +7,10 @@ local mkdir_p = helpers.mkdir_p
 local rmdir = helpers.rmdir
 local nvim_dir = helpers.nvim_dir
 local test_build_dir = helpers.test_build_dir
-local iswin = helpers.iswin
 local nvim_prog = helpers.nvim_prog
+local is_os = helpers.is_os
 
-local nvim_prog_basename = iswin() and 'nvim.exe' or 'nvim'
+local nvim_prog_basename = is_os('win') and 'nvim.exe' or 'nvim'
 
 before_each(clear)
 
@@ -102,7 +102,7 @@ describe('vim.fs', function()
       eq('C:/Users/jdoe', exec_lua [[ return vim.fs.normalize('C:\\Users\\jdoe') ]])
     end)
     it('works with ~', function()
-      if iswin() then
+      if is_os('win') then
         pending([[$HOME does not exist on Windows ¯\_(ツ)_/¯]])
       end
       eq(os.getenv('HOME') .. '/src/foo', exec_lua [[ return vim.fs.normalize('~/src/foo') ]])

test/functional/lua/overrides_spec.lua

@@ -8,12 +8,12 @@ local feed = helpers.feed
 local clear = helpers.clear
 local funcs = helpers.funcs
 local meths = helpers.meths
-local iswin = helpers.iswin
 local command = helpers.command
 local write_file = helpers.write_file
 local exec_capture = helpers.exec_capture
 local exec_lua = helpers.exec_lua
 local pcall_err = helpers.pcall_err
+local is_os = helpers.is_os
 
 local screen
 
@@ -135,7 +135,7 @@ describe('print', function()
         print("very slow")
         vim.api.nvim_command("sleep 1m") -- force deferred event processing
       end
-    ]], (iswin() and "timeout 1") or "sleep 0.1")
+    ]], (is_os('win') and "timeout 1") or "sleep 0.1")
     eq('very slow\nvery fast', exec_capture('lua test()'))
   end)
 end)

test/functional/lua/secure_spec.lua

@@ -5,7 +5,7 @@ local eq = helpers.eq
 local clear = helpers.clear
 local command = helpers.command
 local pathsep = helpers.get_pathsep()
-local iswin = helpers.iswin()
+local is_os = helpers.is_os
 local curbufmeths = helpers.curbufmeths
 local exec_lua = helpers.exec_lua
 local feed_command = helpers.feed_command
@@ -18,7 +18,7 @@ describe('vim.secure', function()
     local xstate = 'Xstate'
 
     setup(function()
-      helpers.mkdir_p(xstate .. pathsep .. (iswin and 'nvim-data' or 'nvim'))
+      helpers.mkdir_p(xstate .. pathsep .. (is_os('win') and 'nvim-data' or 'nvim'))
     end)
 
     teardown(function()

test/functional/lua/uri_spec.lua

@@ -2,7 +2,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local clear = helpers.clear
 local exec_lua = helpers.exec_lua
 local eq = helpers.eq
-local iswin = helpers.iswin
+local is_os = helpers.is_os
 local skip = helpers.skip
 local write_file = require('test.helpers').write_file
 
@@ -169,7 +169,7 @@ describe('URI methods', function()
 
   describe('uri from bufnr', function()
     it('Windows paths should not be treated as uris', function()
-      skip(not iswin(), "Not applicable on non-Windows")
+      skip(not is_os('win'), "Not applicable on non-Windows")
 
       local file = helpers.tmpname()
       write_file(file, 'Test content')