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.

src/env.cpp

@@ -124,10 +124,15 @@ static null_terminated_array_t<char> export_array;
 static bool has_changed_exported = true;
 static void mark_changed_exported() { has_changed_exported = true; }
 
-/// List of all locale variable names.
-static const wchar_t *const locale_variable[] = {L"LANG",       L"LC_ALL",      L"LC_COLLATE",
-                                                 L"LC_CTYPE",   L"LC_MESSAGES", L"LC_MONETARY",
-                                                 L"LC_NUMERIC", L"LC_TIME",     NULL};
+/// List of all locale environment variable names.
+static const wchar_t *const locale_variable[] = {
+    L"LANG",     L"LANGUAGE",          L"LC_ALL",         L"LC_ADDRESS",   L"LC_COLLATE",
+    L"LC_CTYPE", L"LC_IDENTIFICATION", L"LC_MEASUREMENT", L"LC_MESSAGES",  L"LC_MONETARY",
+    L"LC_NAME",  L"LC_NUMERIC",        L"LC_PAPER",       L"LC_TELEPHONE", L"LC_TIME",
+    NULL};
+
+/// List of all curses environment variable names.
+static const wchar_t *const curses_variable[] = {L"TERM", L"TERMINFO", L"TERMINFO_DIRS", NULL};
 
 const var_entry_t *env_node_t::find_entry(const wcstring &key) {
     const var_entry_t *result = NULL;
@@ -200,10 +205,40 @@ static void handle_locale() {
     }
 }
 
+/// Check if the specified variable is a locale variable.
+static bool var_is_curses(const wcstring &key) {
+    for (size_t i = 0; curses_variable[i]; i++) {
+        if (key == curses_variable[i]) {
+            return true;
+        }
+    }
+    return false;
+}
+
+/// Push all curses/terminfo env vars into the global environment where they can be found by those
+/// libraries.
+static void handle_curses() {
+    for (size_t i = 0; curses_variable[i]; i++) {
+        const wchar_t *key = curses_variable[i];
+        const env_var_t var = env_get_string(key);
+        if (!var.empty()) {
+            const std::string &name = wcs2string(key);
+            const std::string &value = wcs2string(var);
+            setenv(name.c_str(), value.c_str(), 1);
+        }
+    }
+    // TODO: Modify input_init() to allow calling it when the terminfo env vars are dynamically
+    // changed. At the present time it can be called just once. Also, we should really only do this
+    // if the TERM var is set.
+    // input_init();
+}
+
 /// React to modifying the given variable.
 static void react_to_variable_change(const wcstring &key) {
     if (var_is_locale(key)) {
         handle_locale();
+    } else if (var_is_curses(key)) {
+        handle_curses();
     } else if (key == L"fish_term256" || key == L"fish_term24bit") {
         update_fish_color_support();
         reader_react_to_color_change();

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.

src/output.cpp

@@ -24,6 +24,7 @@
 
 #include "color.h"
 #include "common.h"
+#include "env.h"
 #include "fallback.h"  // IWYU pragma: keep
 #include "output.h"
 #include "wutil.h"  // IWYU pragma: keep
@@ -33,9 +34,6 @@ static int writeb_internal(char c);
 /// The function used for output.
 static int (*out)(char c) = writeb_internal;
 
-/// Name of terminal.
-static wcstring current_term;
-
 /// Whether term256 and term24bit are supported.
 static color_support_t color_support = 0;
 
@@ -416,18 +414,13 @@ rgb_color_t parse_color(const wcstring &val, bool is_background) {
     return result;
 }
 
-void output_set_term(const wcstring &term) { current_term.assign(term); }
-
-const wchar_t *output_get_term() {
-    return current_term.empty() ? L"<unknown>" : current_term.c_str();
-}
-
 void writembs_check(char *mbs, const char *mbs_name, const char *file, long line) {
     if (mbs != NULL) {
         tputs(mbs, 1, &writeb);
     } else {
+        env_var_t term = env_get_string(L"TERM");
         debug(0, _(L"Tried to use terminfo string %s on line %ld of %s, which is undefined in "
                    L"terminal of type \"%ls\". Please report this error to %s"),
-              mbs_name, line, file, output_get_term(), PACKAGE_BUGREPORT);
+              mbs_name, line, file, term.c_str(), PACKAGE_BUGREPORT);
     }
 }

src/output.h

@@ -76,12 +76,6 @@ void output_set_writer(int (*writer)(char));
 /// Return the current output writer.
 int (*output_get_writer())(char);
 
-/// Set the terminal name.
-void output_set_term(const wcstring &term);
-
-/// Return the terminal name.
-const wchar_t *output_get_term();
-
 /// Sets what colors are supported.
 enum { color_support_term256 = 1 << 0, color_support_term24bit = 1 << 1 };
 typedef unsigned int color_support_t;