py/modsys: Implement optional sys.intern.

Signed-off-by: stijn <stijn@ignitron.net>

py/modsys.c

@@ -147,6 +147,10 @@ STATIC const MP_DEFINE_STR_OBJ(mp_sys_platform_obj, MICROPY_PY_SYS_PLATFORM);
 MP_DEFINE_STR_OBJ(mp_sys_executable_obj, "");
 #endif
 
+#if MICROPY_PY_SYS_INTERN
+MP_DEFINE_CONST_FUN_OBJ_1(mp_sys_intern_obj, mp_obj_str_intern_checked);
+#endif
+
 // exit([retval]): raise SystemExit, with optional argument given to the exception
 STATIC mp_obj_t mp_sys_exit(size_t n_args, const mp_obj_t *args) {
     if (n_args == 0) {
@@ -293,6 +297,10 @@ STATIC const mp_rom_map_elem_t mp_module_sys_globals_table[] = {
     #endif
     #endif
 
+    #if MICROPY_PY_SYS_INTERN
+    { MP_ROM_QSTR(MP_QSTR_intern), MP_ROM_PTR(&mp_sys_intern_obj) },
+    #endif
+
     #if MICROPY_PY_SYS_EXIT
     { MP_ROM_QSTR(MP_QSTR_exit), MP_ROM_PTR(&mp_sys_exit_obj) },
     #endif

py/mpconfig.h

@@ -1434,6 +1434,11 @@ typedef double mp_float_t;
 #define MICROPY_PY_SYS_EXECUTABLE (0)
 #endif
 
+// Whether to provide "sys.intern"
+#ifndef MICROPY_PY_SYS_INTERN
+#define MICROPY_PY_SYS_INTERN (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EVERYTHING)
+#endif
+
 // Whether to provide "sys.exit" function
 #ifndef MICROPY_PY_SYS_EXIT
 #define MICROPY_PY_SYS_EXIT (1)

tests/basics/sys1.py

@@ -23,3 +23,18 @@ if hasattr(sys.implementation, '_mpy'):
 else:
     # Effectively skip subtests
     print(int)
+
+try:
+    print(sys.intern('micropython') == 'micropython')
+    has_intern = True
+except AttributeError:
+    has_intern = False
+    print(True)
+
+if has_intern:
+    try:
+        print(sys.intern(0))
+    except TypeError:
+        print(True)
+else:
+    print(True)

tests/unix/extra_coverage.py.exp

@@ -66,10 +66,10 @@ micropython     machine         math
 
 argv            atexit          byteorder       exc_info
 executable      exit            getsizeof       implementation
-maxsize         modules         path            platform
-print_exception                 ps1             ps2
-stderr          stdin           stdout          tracebacklimit
-version         version_info
+intern          maxsize         modules         path
+platform        print_exception                 ps1
+ps2             stderr          stdin           stdout
+tracebacklimit  version         version_info
 ementation
 # attrtuple
 (start=1, stop=2, step=3)