ports: Move '.frozen' to second entry in sys.path.

In commit 86ce4426 the '.frozen' entry was
added at the start of sys.path, to allow control over when frozen modules
are searched during import, and retain existing behaviour whereby frozen
was searched before the filesystem.

But Python semantics of sys.path require sys.path[0] to be the directory of
the currently executing script, or ''.

This commit moves the '.frozen' entry to second place in sys.path, so
sys.path[0] retains its correct value (described above).
Signed-off-by: Damien George <damien@micropython.org>

ports/unix/main.c

@@ -497,7 +497,7 @@ MP_NOINLINE int main_(int argc, char **argv) {
     if (path == NULL) {
         path = MICROPY_PY_SYS_PATH_DEFAULT;
     }
-    size_t path_num = 2; // [0] is frozen, [1] is for current dir (or base dir of the script)
+    size_t path_num = 1; // [0] is for current dir (or base dir of the script)
     if (*path == PATHLIST_SEP_CHAR) {
         path_num++;
     }
@@ -510,11 +510,10 @@ MP_NOINLINE int main_(int argc, char **argv) {
     mp_obj_list_init(MP_OBJ_TO_PTR(mp_sys_path), path_num);
     mp_obj_t *path_items;
     mp_obj_list_get(mp_sys_path, &path_num, &path_items);
-    path_items[0] = MP_OBJ_NEW_QSTR(MP_QSTR__dot_frozen);
-    path_items[1] = MP_OBJ_NEW_QSTR(MP_QSTR_);
+    path_items[0] = MP_OBJ_NEW_QSTR(MP_QSTR_);
     {
         char *p = path;
-        for (mp_uint_t i = 2; i < path_num; i++) {
+        for (mp_uint_t i = 1; i < path_num; i++) {
             char *p1 = strchr(p, PATHLIST_SEP_CHAR);
             if (p1 == NULL) {
                 p1 = p + strlen(p);
@@ -655,9 +654,9 @@ MP_NOINLINE int main_(int argc, char **argv) {
                 break;
             }
 
-            // Set base dir of the script as second entry in sys.path.
+            // Set base dir of the script as first entry in sys.path.
             char *p = strrchr(basedir, '/');
-            path_items[1] = mp_obj_new_str_via_qstr(basedir, p - basedir);
+            path_items[0] = mp_obj_new_str_via_qstr(basedir, p - basedir);
             free(pathbuf);
 
             set_sys_argv(argv, argc, a);

ports/unix/mpconfigport.h

@@ -125,7 +125,7 @@
 #endif
 #endif
 #ifndef MICROPY_PY_SYS_PATH_DEFAULT
-#define MICROPY_PY_SYS_PATH_DEFAULT "~/.micropython/lib:/usr/lib/micropython"
+#define MICROPY_PY_SYS_PATH_DEFAULT ".frozen:~/.micropython/lib:/usr/lib/micropython"
 #endif
 #define MICROPY_PY_SYS_MAXSIZE      (1)
 #define MICROPY_PY_SYS_STDFILES     (1)

ports/unix/variants/minimal/mpconfigvariant.h

@@ -89,7 +89,7 @@
 #define MICROPY_PY_SYS_EXIT         (0)
 #define MICROPY_PY_SYS_PLATFORM     "linux"
 #ifndef MICROPY_PY_SYS_PATH_DEFAULT
-#define MICROPY_PY_SYS_PATH_DEFAULT "~/.micropython/lib:/usr/lib/micropython"
+#define MICROPY_PY_SYS_PATH_DEFAULT ".frozen:~/.micropython/lib:/usr/lib/micropython"
 #endif
 #define MICROPY_PY_SYS_MAXSIZE      (0)
 #define MICROPY_PY_SYS_STDFILES     (0)

ports/windows/mpconfigport.h

@@ -90,7 +90,7 @@
 #define MICROPY_PY_SYS_ATEXIT       (1)
 #define MICROPY_PY_SYS_PLATFORM     "win32"
 #ifndef MICROPY_PY_SYS_PATH_DEFAULT
-#define MICROPY_PY_SYS_PATH_DEFAULT "~/.micropython/lib"
+#define MICROPY_PY_SYS_PATH_DEFAULT ".frozen;~/.micropython/lib"
 #endif
 #define MICROPY_PY_SYS_MAXSIZE      (1)
 #define MICROPY_PY_SYS_STDFILES     (1)

py/runtime.c

@@ -124,10 +124,10 @@ void mp_init(void) {
 
     #if MICROPY_PY_SYS_PATH_ARGV_DEFAULTS
     mp_obj_list_init(MP_OBJ_TO_PTR(mp_sys_path), 0);
+    mp_obj_list_append(mp_sys_path, MP_OBJ_NEW_QSTR(MP_QSTR_)); // current dir (or base dir of the script)
     #if MICROPY_MODULE_FROZEN
     mp_obj_list_append(mp_sys_path, MP_OBJ_NEW_QSTR(MP_QSTR__dot_frozen));
     #endif
-    mp_obj_list_append(mp_sys_path, MP_OBJ_NEW_QSTR(MP_QSTR_)); // current dir (or base dir of the script)
     mp_obj_list_init(MP_OBJ_TO_PTR(mp_sys_argv), 0);
     #endif
 

tests/basics/sys_path.py

+# test sys.path
+
+try:
+    import usys as sys
+except ImportError:
+    import sys
+
+# check that this script was executed from a file of the same name
+if "__file__" not in globals() or "sys_path.py" not in __file__:
+    print("SKIP")
+    raise SystemExit
+
+# test that sys.path[0] is the directory containing this script
+with open(sys.path[0] + "/sys_path.py") as f:
+    for _ in range(4):
+        print(f.readline())

tests/run-tests.py

@@ -852,7 +852,7 @@ the last matching regex is used:
 
     if not args.keep_path:
         # clear search path to make sure tests use only builtin modules and those in extmod
-        os.environ["MICROPYPATH"] = os.pathsep + base_path("../extmod")
+        os.environ["MICROPYPATH"] = ".frozen" + os.pathsep + base_path("../extmod")
 
     try:
         os.makedirs(args.result_dir, exist_ok=True)