CLI: Fix long delay with quick connect/disconnect

applications/services/cli/cli_vcp.c

@@ -218,6 +218,11 @@ static void cli_vcp_internal_event_happened(FuriEventLoopObject* object, void* c
         pipe_detach_from_event_loop(cli_vcp->own_pipe);
         pipe_free(cli_vcp->own_pipe);
         cli_vcp->own_pipe = NULL;
+
+        // wait for shell to stop
+        cli_shell_join(cli_vcp->shell);
+        cli_shell_free(cli_vcp->shell);
+        pipe_free(cli_vcp->shell_pipe);
         break;
     }
 
@@ -226,14 +231,6 @@ static void cli_vcp_internal_event_happened(FuriEventLoopObject* object, void* c
         FURI_LOG_D(TAG, "Connected");
         cli_vcp->is_connected = true;
 
-        // wait for previous shell to stop
-        furi_check(!cli_vcp->own_pipe);
-        if(cli_vcp->shell) {
-            cli_shell_join(cli_vcp->shell);
-            cli_shell_free(cli_vcp->shell);
-            pipe_free(cli_vcp->shell_pipe);
-        }
-
         // start shell thread
         PipeSideBundle bundle = pipe_alloc(VCP_BUF_SIZE, 1);
         cli_vcp->own_pipe = bundle.alices_side;

lib/toolbox/cli/shell/cli_shell.c

@@ -16,7 +16,8 @@
 
 #define TAG "CliShell"
 
-#define ANSI_TIMEOUT_MS 10
+#define ANSI_TIMEOUT_MS             10
+#define TRANSIENT_SESSION_WINDOW_MS 100
 
 typedef enum {
     CliShellComponentCompletions,
@@ -415,10 +416,15 @@ static void cli_shell_deinit(CliShell* shell) {
 static int32_t cli_shell_thread(void* context) {
     CliShell* shell = context;
 
-    // Sometimes, the other side closes the pipe even before our thread is started. Although the
-    // rest of the code will eventually find this out if this check is removed, there's no point in
-    // wasting time.
-    if(pipe_state(shell->pipe) == PipeStateBroken) return 0;
+    // Sometimes, the other side (e.g. qFlipper) closes the pipe even before our thread is started.
+    // Although the rest of the code will eventually find this out if this check is removed,
+    // there's no point in wasting time. This gives qFlipper a chance to quickly close and re-open
+    // the session.
+    const size_t delay_step = 10;
+    for(size_t i = 0; i < TRANSIENT_SESSION_WINDOW_MS / delay_step; i++) {
+        furi_delay_ms(delay_step);
+        if(pipe_state(shell->pipe) == PipeStateBroken) return 0;
+    }
 
     cli_shell_init(shell);
     FURI_LOG_D(TAG, "Started");