don't enter safemode.py on USER safe mode

Author: dhalbert

README.rst

@@ -139,8 +139,10 @@ Behavior
    possible to fix code that causes nasty crashes by making it available through mass storage after
    the crash. A reset (the button) is needed after it's fixed to get back into normal mode.
 -  Safe mode may be handled programmatically by providing a ``safemode.py``.
-   ``safemode.py`` is run if the board has reset due to entering safe mode. USB is not
-   available so nothing can be printed. ``safemode.py`` can determine why the safe mode occurred
+   ``safemode.py`` is run if the board has reset due to entering safe mode, unless the safe mode
+   initiated by the user by pressing button(s).
+   USB is not available so nothing can be printed.
+   ``safemode.py`` can determine why the safe mode occurred
    using ``supervisor.runtime.safe_mode_reason``, and take appropriate action. For instance,
    if a hard crash occurred, ``safemode.py`` may do a ``microcontroller.reset()``
    to automatically restart despite the crash.

main.c

@@ -733,7 +733,9 @@ vstr_t *boot_output;
 #if CIRCUITPY_SAFEMODE_PY
 STATIC void __attribute__ ((noinline)) run_safemode_py(safe_mode_t safe_mode) {
     // Don't run if we aren't in safe mode or we won't be able to find safemode.py.
-    if (safe_mode == SAFE_MODE_NONE || !filesystem_present()) {
+    // Also don't run if it's a user-initiated safemode (pressing button(s) during boot),
+    // since that's deliberate.
+    if (safe_mode == SAFE_MODE_NONE || safe_mode == SAFE_MODE_USER || !filesystem_present()) {
         return;
     }
 

shared-bindings/supervisor/SafeModeReason.c

@@ -137,7 +137,11 @@ MAKE_ENUM_MAP(supervisor_safe_mode_reason) {
     MAKE_ENUM_MAP_ENTRY(safe_mode_reason, USB_TOO_MANY_INTERFACE_NAMES),
 
 //|     USER: object
-//|     """The user pressed one or more buttons to enter safe mode."""
+//|     """The user pressed one or more buttons to enter safe mode.
+//|     This safe mode does **not** cause ``safemode.py`` to be run, since its purpose
+//|     is to prevent all user code from running.
+//|     This allows errors in ``safemode.py`` to be corrected easily.
+//|     """
 //|
     MAKE_ENUM_MAP_ENTRY(safe_mode_reason, USER),