put curses/terminfo vars into the environment

We need to actually export the curses/terminfo env vars in order for
`setupterm()` to be able to use them. While fixing this I reworked the
fallback logic implemented by @zanchey in response to issue #1060 in
order to simplify the logic and clarify the error messages.

This does not allow someone to change the curses/terminfo env vars after
the first prompt is displayed (you can but it won't affect the current
fish process). It only makes it possible to set `TERM`, `TERMINFO`, and
`TERMINFO_DIRS` in *config.fish* or similar config file and have them be
honored by fish.

1 files changed, 11 insertions, 22 deletions

diff --git a/src/input.cpp b/src/input.cpp
index 5b599e85..b9132b2c 100644
--- a/src/input.cpp
+++ b/src/input.cpp
@@ -1,7 +1,6 @@
 // Functions for reading a character of input from stdin.
 #include "config.h"
 
-#include <assert.h>
 #include <errno.h>
 #include <unistd.h>
 #include <wchar.h>
@@ -339,35 +338,25 @@ void update_fish_color_support(void) {
 
 int input_init() {
     if (is_init) return 1;
-
     is_init = true;
-
     input_common_init(&interrupt_handler);
 
-    const env_var_t term = env_get_string(L"TERM");
-    int errret;
-    if (setupterm(const_cast<char *>(wcs2string(term).c_str()), STDOUT_FILENO, &errret) == ERR) {
-        debug(0, _(L"Could not set up terminal"));
-        if (errret == 0) {
-            debug(0, _(L"Check that your terminal type, '%ls', is supported on this system"),
-                  term.c_str());
-            debug(0, _(L"Attempting to use '%ls' instead"), DEFAULT_TERM);
-            env_set(L"TERM", DEFAULT_TERM, ENV_GLOBAL | ENV_EXPORT);
-            const std::string default_term = wcs2string(DEFAULT_TERM);
-            if (setupterm(const_cast<char *>(default_term.c_str()), STDOUT_FILENO, &errret) ==
-                ERR) {
-                debug(0, _(L"Could not set up terminal"));
-                exit_without_destructors(1);
-            }
-        } else {
+    int err_ret;
+    if (setupterm(NULL, STDOUT_FILENO, &err_ret) == ERR) {
+        env_var_t term = env_get_string(L"TERM");
+        debug(0, _(L"Your TERM value of '%ls' is not valid"), term.c_str());
+        debug(0, _(L"Check that your terminal type is supported on this system"));
+        env_set(L"TERM", DEFAULT_TERM, ENV_GLOBAL | ENV_EXPORT);
+        if (setupterm(NULL, STDOUT_FILENO, &err_ret) == ERR) {
+            debug(0, _(L"Unable to setup terminal using your TERM or the '%ls' fallback"),
+                  DEFAULT_TERM);
             exit_without_destructors(1);
+        } else {
+            debug(0, _(L"Using fallback terminal type '%ls' instead"), DEFAULT_TERM);
         }
     }
-    assert(!term.missing());
-    output_set_term(term);
 
     input_terminfo_init();
-
     update_fish_color_support();
 
     // If we have no keybindings, add a few simple defaults.