refactor(tests): merge n.spawn/n.spawn_argv into n.new_session #31859

Problem:
- `n.spawn()` is misleading because it also connects RPC, it's not just
  "spawning" a process.
- It's confusing that `n.spawn()` and `n.spawn_argv()` are separate.

Solution:
- Replace `n.spawn()`/`n.spawn_argv()` with a single function `n.new_session()`.
  This name aligns with the existing functions `n.set_session`/`n.get_session`.
    - Note: removes direct handling of `prepend_argv`, but I doubt that was
      important or intentional. If callers want to control use of `prepend_argv`
      then we should add a new flag to `test.session.Opts`.
- Move `keep` to first parameter of `n.new_session()`.
- Add a `merge` flag to `test.session.Opts`
- Mark `_new_argv()` as private. Test should use clear/new_session/spawn_wait
  instead.

2 files changed, 16 insertions, 12 deletions

diff --git a/test/functional/shada/marks_spec.lua b/test/functional/shada/marks_spec.lua
index d680f0b83b..837978dee1 100644
--- a/test/functional/shada/marks_spec.lua
+++ b/test/functional/shada/marks_spec.lua
@@ -218,7 +218,7 @@ describe('ShaDa support code', function()
   -- -c temporary sets lnum to zero to make `+/pat` work, so calling setpcmark()
   -- during -c used to add item with zero lnum to jump list.
   it('does not create incorrect file for non-existent buffers when writing from -c', function()
-    local argv = n.new_argv {
+    local p = n.spawn_wait {
       args_rm = {
         '-i',
         '--embed', -- no --embed
@@ -232,12 +232,13 @@ describe('ShaDa support code', function()
         'qall',
       },
     }
-    eq('', fn.system(argv))
+    eq('', p:output())
+    eq(0, p.status)
     eq(0, exc_exec('rshada'))
   end)
 
   it('does not create incorrect file for non-existent buffers opened from -c', function()
-    local argv = n.new_argv {
+    local p = n.spawn_wait {
       args_rm = {
         '-i',
         '--embed', -- no --embed
@@ -251,7 +252,8 @@ describe('ShaDa support code', function()
         'autocmd VimEnter * qall',
       },
     }
-    eq('', fn.system(argv))
+    eq('', p:output())
+    eq(0, p.status)
     eq(0, exc_exec('rshada'))
   end)
 
diff --git a/test/functional/shada/shada_spec.lua b/test/functional/shada/shada_spec.lua
index 5debdc6c77..78fe19b984 100644
--- a/test/functional/shada/shada_spec.lua
+++ b/test/functional/shada/shada_spec.lua
@@ -6,8 +6,7 @@ local uv = vim.uv
 local paths = t.paths
 
 local api, nvim_command, fn, eq = n.api, n.command, n.fn, t.eq
-local write_file, spawn, set_session, nvim_prog, exc_exec =
-  t.write_file, n.spawn, n.set_session, n.nvim_prog, n.exc_exec
+local write_file, set_session, exc_exec = t.write_file, n.set_session, n.exc_exec
 local is_os = t.is_os
 local skip = t.skip
 
@@ -254,7 +253,7 @@ describe('ShaDa support code', function()
   it('does not crash when ShaDa file directory is not writable', function()
     skip(is_os('win'))
 
-    fn.mkdir(dirname, '', 0)
+    fn.mkdir(dirname, '', '0')
     eq(0, fn.filewritable(dirname))
     reset { shadafile = dirshada, args = { '--cmd', 'set shada=' } }
     api.nvim_set_option_value('shada', "'10", {})
@@ -270,10 +269,10 @@ end)
 
 describe('ShaDa support code', function()
   it('does not write NONE file', function()
-    local session = spawn(
-      { nvim_prog, '-u', 'NONE', '-i', 'NONE', '--embed', '--headless', '--cmd', 'qall' },
-      true
-    )
+    local session = n.new_session(false, {
+      merge = false,
+      args = { '-u', 'NONE', '-i', 'NONE', '--embed', '--headless', '--cmd', 'qall' },
+    })
     session:close()
     eq(nil, uv.fs_stat('NONE'))
     eq(nil, uv.fs_stat('NONE.tmp.a'))
@@ -281,7 +280,10 @@ describe('ShaDa support code', function()
 
   it('does not read NONE file', function()
     write_file('NONE', '\005\001\015\131\161na\162rX\194\162rc\145\196\001-')
-    local session = spawn({ nvim_prog, '-u', 'NONE', '-i', 'NONE', '--embed', '--headless' }, true)
+    local session = n.new_session(
+      false,
+      { merge = false, args = { '-u', 'NONE', '-i', 'NONE', '--embed', '--headless' } }
+    )
     set_session(session)
     eq('', fn.getreg('a'))
     session:close()