feat(i18n): start each session in the language its SSH client sends

include/ssh_server.h

@@ -65,6 +65,8 @@ typedef struct client {
     char ssh_login[MAX_USERNAME_LEN];
     char session_id[32];             /* Opaque id an identity module sees */
     char key_fingerprint[TNT_IDENTITY_FINGERPRINT_SIZE];  /* Signed SSH key */
+    bool has_client_lang;            /* The client sent LANG or LC_* */
+    ui_lang_t client_lang;
     time_t connect_time;
     time_t last_active;
     atomic_bool redraw_pending;

src/bootstrap.c

@@ -1,6 +1,7 @@
 #include "bootstrap.h"
 #include "client.h"
 #include "common.h"
+#include "i18n.h"
 #include "identity.h"
 #include "input.h"
 #include "ratelimit.h"
@@ -27,6 +28,8 @@ typedef struct {
     char client_ip[INET6_ADDRSTRLEN];
     char requested_user[MAX_USERNAME_LEN];
     char key_fingerprint[TNT_IDENTITY_FINGERPRINT_SIZE];
+    int lang_rank;              /* 0 none, 1 LANG, 2 LC_MESSAGES, 3 LC_ALL */
+    ui_lang_t lang;
     int pty_width;
     int pty_height;
     char exec_command[MAX_EXEC_COMMAND_LEN];
@@ -422,6 +425,28 @@ static int channel_pty_window_change(ssh_session session, ssh_channel channel,
     return SSH_OK;
 }
 
+/* OpenSSH clients send LANG and LC_* by default (SendEnv), which lets each
+ * session start in its own language.  Nothing is exported to the process. */
+static int channel_env_request(ssh_session session, ssh_channel channel,
+                               const char *name, const char *value,
+                               void *userdata) {
+    (void)session;
+    (void)channel;
+    session_context_t *ctx = (session_context_t *)userdata;
+    int rank = !name                          ? 0
+               : strcmp(name, "LC_ALL") == 0      ? 3
+               : strcmp(name, "LC_MESSAGES") == 0 ? 2
+               : strcmp(name, "LANG") == 0        ? 1
+                                                  : 0;
+    ui_lang_t lang;
+
+    if (rank > ctx->lang_rank && i18n_try_parse_ui_lang(value, &lang)) {
+        ctx->lang_rank = rank;
+        ctx->lang = lang;
+    }
+    return SSH_OK;
+}
+
 /* Shell request callback */
 static int channel_shell_request(ssh_session session, ssh_channel channel,
                                  void *userdata) {
@@ -478,6 +503,7 @@ static void setup_session_channel_callbacks(ssh_channel channel,
     ctx->channel_cb->channel_shell_request_function = channel_shell_request;
     ctx->channel_cb->channel_pty_window_change_function = channel_pty_window_change;
     ctx->channel_cb->channel_exec_request_function = channel_exec_request;
+    ctx->channel_cb->channel_env_request_function = channel_env_request;
 
     ssh_set_channel_callbacks(channel, ctx->channel_cb);
 }
@@ -681,6 +707,8 @@ void *bootstrap_run(void *arg) {
     }
     snprintf(client->key_fingerprint, sizeof(client->key_fingerprint), "%s",
              ctx->key_fingerprint);
+    client->has_client_lang = ctx->lang_rank > 0;
+    client->client_lang = ctx->lang;
     if (ctx->exec_command[0] != '\0') {
         strncpy(client->exec_command, ctx->exec_command,
                 sizeof(client->exec_command) - 1);

src/input.c

@@ -1642,7 +1642,7 @@ void input_run_session(client_t *client) {
      * leaves `ssh vim@host` free to mean "give me the vim keys". */
     client->keymap = tnt_keymap_from_login(client->ssh_login, g_default_keymap);
     client->follow_tail = true;
-    client->ui_lang = g_default_ui_lang;
+    client->ui_lang = client->has_client_lang ? client->client_lang : g_default_ui_lang;
     client->connected = true;
     client->command_history_count = 0;
     client->command_history_pos = 0;

tests/run_suites.sh

@@ -2,6 +2,9 @@
 set -u
 
 BASE_PORT=${PORT:-2222}
+# ssh forwards these (SendEnv), and a session follows them over the server's
+# TNT_LANG, so a developer's locale would change what the suites see.
+unset LANG LC_ALL LC_MESSAGES
 JOBS=${INTEGRATION_JOBS:-4}
 
 # Slowest first, so the last job slot never waits on a long suite.
@@ -23,7 +26,8 @@ vim_keymap 12
 wide_text_view 9
 module_privileged 16
 identity 17
-module_private 18"
+module_private 18
+client_lang 19"
 
 WORK_DIR=$(mktemp -d "${TMPDIR:-/tmp}/tnt-suites.XXXXXX")
 trap 'rm -rf "$WORK_DIR"' EXIT

tests/test_client_lang.sh

@@ -0,0 +1,83 @@
+#!/bin/bash
+# Each session starts in the language its SSH client sends with LANG or LC_*.
+
+BIN="../tnt"
+PORT=${PORT:-2222}
+PASS=0
+FAIL=0
+STATE_DIR=$(mktemp -d "${TMPDIR:-/tmp}/tnt-client-lang-test.XXXXXX")
+SERVER_PID=""
+
+cleanup() {
+    if [ -n "$SERVER_PID" ]; then
+        kill "$SERVER_PID" 2>/dev/null || true
+        wait "$SERVER_PID" 2>/dev/null || true
+    fi
+    rm -rf "$STATE_DIR"
+}
+trap cleanup EXIT
+
+if [ ! -f "$BIN" ]; then
+    echo "Error: Binary $BIN not found."
+    exit 1
+fi
+
+SSH_BASE="-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o PubkeyAuthentication=no -o ConnectionAttempts=3 -o ConnectTimeout=15 -o SendEnv=-* -p $PORT"
+
+wait_for_health() {
+    for _ in $(seq 1 15); do
+        [ "$(ssh -n $SSH_BASE localhost health 2>/dev/null)" = "ok" ] && return 0
+        sleep 1
+    done
+    return 1
+}
+
+# Prints which prompt language the session showed: zh, en or none.
+prompt_language() {
+    local name="$1"
+    shift
+    local script="$STATE_DIR/$name.expect"
+    cat >"$script" <<EOF
+set timeout 10
+spawn env -u LANG -u LC_ALL -u LC_MESSAGES ssh $SSH_BASE $* localhost
+expect {
+    "请输入用户名" { puts "\nLANGUAGE=zh"; send -- "\003"; exit 0 }
+    "Enter display name" { puts "\nLANGUAGE=en"; send -- "\003"; exit 0 }
+    timeout { puts "\nLANGUAGE=none"; exit 0 }
+}
+EOF
+    expect "$script" 2>&1 | sed -n 's/^LANGUAGE=//p' | tr -d '\r'
+}
+
+check() {
+    local description="$1" want="$2" got="$3"
+    if [ "$got" = "$want" ]; then
+        echo "✓ $description"
+        PASS=$((PASS + 1))
+    else
+        echo "✗ $description (want $want, got $got)"
+        FAIL=$((FAIL + 1))
+    fi
+}
+
+echo "=== TNT Client Language Tests ==="
+
+TNT_LANG=en TNT_RATE_LIMIT=0 "$BIN" -p "$PORT" -d "$STATE_DIR" >"$STATE_DIR/server.log" 2>&1 &
+SERVER_PID=$!
+if ! wait_for_health; then
+    echo "✗ server did not start"
+    cat "$STATE_DIR/server.log"
+    exit 1
+fi
+
+check "LANG=zh_CN.UTF-8 starts in Chinese" zh "$(prompt_language zh -o SetEnv=LANG=zh_CN.UTF-8)"
+check "LC_ALL wins over LANG" zh "$(prompt_language lcall '-o "SetEnv=LANG=en_US.UTF-8 LC_ALL=zh_CN.UTF-8"')"
+check "LANG=en_US.UTF-8 keeps English" en "$(prompt_language en -o SetEnv=LANG=en_US.UTF-8)"
+check "an unknown locale falls back to the server default" en "$(prompt_language other -o SetEnv=LANG=fr_FR.UTF-8)"
+check "no locale falls back to the server default" en "$(prompt_language none)"
+
+echo ""
+echo "PASSED: $PASS"
+echo "FAILED: $FAIL"
+[ "$FAIL" -eq 0 ] && echo "All tests passed"
+exit "$FAIL"

tnt-chat.7

@@ -519,6 +519,12 @@ The default is
 .TQ
 .BI ":language " [en|zh]
 Show or set the session interface language.
+A session starts in the language the SSH client sends in
+.BR LC_ALL ,
+.B LC_MESSAGES
+or
+.BR LANG ,
+when it is English or Chinese, and in the server's language otherwise.
 .TP
 .B :help
 Open the concise interactive manual.

tnt.8

@@ -239,6 +239,10 @@ An invalid explicit value selects English.
 Select the language when
 .B TNT_LANG
 is unset, in the precedence shown.
+A session whose SSH client sends one of these variables, as OpenSSH does by
+default with
+.BR SendEnv ,
+starts in that language instead; otherwise it uses the server's.
 .TP
 .B TNT_MAX_CONNECTIONS
 Global connection limit.