fix(pty): Always use $TERM from the job's env dict

Before #12937, the only way to specify the `$TERM` for a pty job was
through the `TERM` key in the job's opts dict.  This was shuttled to the
child process throug a special field on the PtyProcess object and
injected into the environment after forking.

Now that we have a proper way to specify the environment for a job, we
can simply ensure that the env dict has a proper `TERM` set and avoid
the extra shuttling of data around.

This deprecates the use of the `TERM` option, but will still honor it if
present, although at a lower priority than a `TERM` present in the env
dict.

This also fixes #13874 because we're no longer trying to overwrite
`TERM` in the env dict with the special pty `term_name`.  Doing so
raises an internal error because of the existing key which, under
certain circumstances, would cause the "hit enter" prompt.  However,
since the child process had already forked, there was no way for the
user to acknowledge the prompt and we would just hang there.

1 files changed, 26 insertions, 9 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 1a7bbf2d0e..8788d7ea88 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -4912,7 +4912,8 @@ static const char *required_env_vars[] = {
 
 static dict_T *create_environment(const dictitem_T *job_env,
                                   const bool clear_env,
-                                  const bool pty)
+                                  const bool pty,
+                                  const char * const pty_term_name)
 {
   dict_T * env = tv_dict_alloc();
 
@@ -4946,6 +4947,18 @@ static dict_T *create_environment(const dictitem_T *job_env,
     }
   }
 
+  // For a pty, we need a sane $TERM set.  We can't rely on nvim's environment,
+  // because the child process is going to be communicating with nvim, not the
+  // parent terminal.  Set a sane default, but let the user override it in the
+  // job's environment if they want.
+  if (pty) {
+    dictitem_T *dv = tv_dict_find(env, S_LEN("TERM"));
+    if (dv) {
+      tv_dict_item_remove(env, dv);
+    }
+    tv_dict_add_str(env, S_LEN("TERM"), pty_term_name);
+  }
+
   if (job_env) {
     tv_dict_extend(env, job_env->di_tv.vval.v_dict, "force");
   }
@@ -5055,20 +5068,25 @@ static void f_jobstart(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     }
   }
 
-  env = create_environment(job_env, clear_env, pty);
-
   uint16_t width = 0, height = 0;
   char *term_name = NULL;
 
   if (pty) {
     width = (uint16_t)tv_dict_get_number(job_opts, "width");
     height = (uint16_t)tv_dict_get_number(job_opts, "height");
-    term_name = tv_dict_get_string(job_opts, "TERM", true);
+    // Legacy method, before env option existed, to specify $TERM.  No longer
+    // documented, but still usable to avoid breaking scripts.
+    term_name = tv_dict_get_string(job_opts, "TERM", false);
+    if (!term_name) {
+      term_name = "ansi";
+    }
   }
 
+  env = create_environment(job_env, clear_env, pty, term_name);
+
   Channel *chan = channel_job_start(argv, on_stdout, on_stderr, on_exit, pty,
                                     rpc, overlapped, detach, cwd, width, height,
-                                    term_name, env, &rettv->vval.v_number);
+                                    env, &rettv->vval.v_number);
   if (chan) {
     channel_create_event(chan, NULL);
   }
@@ -7511,7 +7529,7 @@ static void f_rpcstart(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   Channel *chan = channel_job_start(argv, CALLBACK_READER_INIT,
                                     CALLBACK_READER_INIT, CALLBACK_NONE,
                                     false, true, false, false, NULL, 0, 0,
-                                    NULL, NULL, &rettv->vval.v_number);
+                                    NULL, &rettv->vval.v_number);
   if (chan) {
     channel_create_event(chan, NULL);
   }
@@ -10618,7 +10636,7 @@ static void f_termopen(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     }
   }
 
-  env = create_environment(job_env, clear_env, pty);
+  env = create_environment(job_env, clear_env, pty, "xterm-256color");
 
   const bool rpc = false;
   const bool overlapped = false;
@@ -10627,8 +10645,7 @@ static void f_termopen(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   Channel *chan = channel_job_start(argv, on_stdout, on_stderr, on_exit,
                                     pty, rpc, overlapped, detach, cwd,
                                     term_width, curwin->w_height_inner,
-                                    xstrdup("xterm-256color"), env,
-                                    &rettv->vval.v_number);
+                                    env, &rettv->vval.v_number);
   if (rettv->vval.v_number <= 0) {
     return;
   }