sys/shell: Add optional hooks for shell commands

Introduce optional user shell_post_readline_hook, shell_pre_command_hook, shell_post_command_hook.
Enable with USEMODULE=shell_hooks.
Calls user implemented *_hook functions if defined.
If implementation does not exist, nothing happens.

The intent is to make profiling of the shell command timings easier.

Test provided in tests/shell with USEMODULE=shell_hooks.

makefiles/pseudomodules.inc.mk

@@ -98,6 +98,7 @@ PSEUDOMODULES += saul_nrf_temperature
 PSEUDOMODULES += scanf_float
 PSEUDOMODULES += sched_cb
 PSEUDOMODULES += semtech_loramac_rx
+PSEUDOMODULES += shell_hooks
 PSEUDOMODULES += slipdev_stdio
 PSEUDOMODULES += sock
 PSEUDOMODULES += sock_async

sys/include/shell.h

@@ -48,6 +48,37 @@ extern "C" {
  */
 #define SHELL_DEFAULT_BUFSIZE   (128)
 
+/**
+ * @brief           Optional hook after readline has triggered.
+ * @details         User implemented function gets called after the shell
+ *                  readline is complete.
+ * @note            Only executed with the `shell_hooks` module.
+ */
+void shell_post_readline_hook(void);
+
+/**
+ * @brief           Optional hook before shell command is called.
+ * @details         User implemented function gets called before a valid shell
+ *                  command will be called.
+ * @note            Only executed with the `shell_hooks` module.
+ *
+ * @param[in]       argc   Number of arguments supplied to the function invocation.
+ * @param[in]       argv   The supplied argument list.
+ */
+void shell_pre_command_hook(int argc, char **argv);
+
+/**
+ * @brief           Optional hook after shell command is called.
+ * @details         User implemented function gets called before a valid shell
+ *                  command will be called.
+ * @note            Only executed with the `shell_hooks` module.
+ *
+ * @param[in]       ret    Return value of the shell command.
+ * @param[in]       argc   Number of arguments supplied to the function invocation.
+ * @param[in]       argv   The supplied argument list.
+ */
+void shell_post_command_hook(int ret, int argc, char **argv);
+
 /**
  * @brief           Protype of a shell callback handler.
  * @details         The functions supplied to shell_run() must use this signature.

sys/shell/shell.c

@@ -199,7 +199,9 @@ static void handle_input_line(const shell_command_t *command_list, char *line)
     char *writepos = readpos;
 
     uint8_t pstate = PARSE_BLANK;
-
+    if (IS_USED(MODULE_SHELL_HOOKS)) {
+        shell_post_readline_hook();
+    }
     for (; *readpos != '\0'; readpos++) {
 
         char wordbreak = SPACE;
@@ -300,7 +302,14 @@ static void handle_input_line(const shell_command_t *command_list, char *line)
     /* then we call the appropriate handler */
     shell_command_handler_t handler = find_handler(command_list, argv[0]);
     if (handler != NULL) {
-        handler(argc, argv);
+        if (IS_USED(MODULE_SHELL_HOOKS)) {
+            shell_pre_command_hook(argc, argv);
+            int res = handler(argc, argv);
+            shell_post_command_hook(res, argc, argv);
+        }
+        else {
+            handler(argc, argv);
+        }
     }
     else {
         if (strcmp("help", argv[0]) == 0) {
@@ -312,6 +321,25 @@ static void handle_input_line(const shell_command_t *command_list, char *line)
     }
 }
 
+__attribute__((weak)) void shell_post_readline_hook(void)
+{
+
+}
+
+__attribute__((weak)) void shell_pre_command_hook(int argc, char **argv)
+{
+    (void)argv;
+    (void)argc;
+}
+
+__attribute__((weak)) void shell_post_command_hook(int ret, int argc,
+                                                   char **argv)
+{
+    (void)ret;
+    (void)argv;
+    (void)argc;
+}
+
 static inline void print_prompt(void)
 {
     if (PROMPT_ON) {

tests/shell/main.c

@@ -28,6 +28,28 @@
 #include "xtimer.h"
 #endif
 
+#if MODULE_SHELL_HOOKS
+void shell_post_readline_hook(void)
+{
+    puts("shell_post_readline_hook");
+}
+
+void shell_pre_command_hook(int argc, char **argv)
+{
+    (void)argc;
+    (void)argv;
+    puts("shell_pre_command_hook");
+}
+
+void shell_post_command_hook(int ret, int argc, char **argv)
+{
+    (void)ret;
+    (void)argc;
+    (void)argv;
+    puts("shell_post_command_hook");
+}
+#endif
+
 static int print_teststart(int argc, char **argv)
 {
     (void) argc;