bpo-42260: Add _PyConfig_FromDict() (GH-23167)

* Rename config_as_dict() to _PyConfig_AsDict().
* Add 'module_search_paths_set' to _PyConfig_AsDict().
* Add _PyConfig_FromDict().
* Add get_config() and set_config() to _testinternalcapi.
* Add config_check_consistency().

2 files changed, 356 insertions, 58 deletions

diff --git a/Python/initconfig.c b/Python/initconfig.c
index de496ac..d54d5b7 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -577,6 +577,74 @@ Py_GetArgcArgv(int *argc, wchar_t ***argv)
      ? _PyStatus_ERR("cannot decode " NAME) \
      : _PyStatus_NO_MEMORY())
 
+#define MAX_HASH_SEED 4294967295UL
+
+
+#ifndef NDEBUG
+static int
+config_check_consistency(const PyConfig *config)
+{
+    /* Check config consistency */
+    assert(config->isolated >= 0);
+    assert(config->use_environment >= 0);
+    assert(config->dev_mode >= 0);
+    assert(config->install_signal_handlers >= 0);
+    assert(config->use_hash_seed >= 0);
+    assert(config->hash_seed <= MAX_HASH_SEED);
+    assert(config->faulthandler >= 0);
+    assert(config->tracemalloc >= 0);
+    assert(config->import_time >= 0);
+    assert(config->show_ref_count >= 0);
+    assert(config->dump_refs >= 0);
+    assert(config->malloc_stats >= 0);
+    assert(config->site_import >= 0);
+    assert(config->bytes_warning >= 0);
+    assert(config->inspect >= 0);
+    assert(config->interactive >= 0);
+    assert(config->optimization_level >= 0);
+    assert(config->parser_debug >= 0);
+    assert(config->write_bytecode >= 0);
+    assert(config->verbose >= 0);
+    assert(config->quiet >= 0);
+    assert(config->user_site_directory >= 0);
+    assert(config->parse_argv >= 0);
+    assert(config->configure_c_stdio >= 0);
+    assert(config->buffered_stdio >= 0);
+    assert(config->program_name != NULL);
+    assert(_PyWideStringList_CheckConsistency(&config->orig_argv));
+    assert(_PyWideStringList_CheckConsistency(&config->argv));
+    /* sys.argv must be non-empty: empty argv is replaced with [''] */
+    assert(config->argv.length >= 1);
+    assert(_PyWideStringList_CheckConsistency(&config->xoptions));
+    assert(_PyWideStringList_CheckConsistency(&config->warnoptions));
+    assert(_PyWideStringList_CheckConsistency(&config->module_search_paths));
+    assert(config->module_search_paths_set >= 0);
+    if (config->_install_importlib) {
+        /* don't check config->module_search_paths */
+        assert(config->executable != NULL);
+        assert(config->base_executable != NULL);
+        assert(config->prefix != NULL);
+        assert(config->base_prefix != NULL);
+        assert(config->exec_prefix != NULL);
+        assert(config->base_exec_prefix != NULL);
+    }
+    assert(config->platlibdir != NULL);
+    assert(config->filesystem_encoding != NULL);
+    assert(config->filesystem_errors != NULL);
+    assert(config->stdio_encoding != NULL);
+    assert(config->stdio_errors != NULL);
+#ifdef MS_WINDOWS
+    assert(config->legacy_windows_stdio >= 0);
+#endif
+    /* -c and -m options are exclusive */
+    assert(!(config->run_command != NULL && config->run_module != NULL));
+    assert(config->check_hash_pycs_mode != NULL);
+    assert(config->_install_importlib >= 0);
+    assert(config->pathconfig_warnings >= 0);
+    return 1;
+}
+#endif
+
 
 /* Free memory allocated in config, but don't clear all attributes */
 void
@@ -880,8 +948,8 @@ _PyConfig_Copy(PyConfig *config, const PyConfig *config2)
 }
 
 
-static PyObject *
-config_as_dict(const PyConfig *config)
+PyObject *
+_PyConfig_AsDict(const PyConfig *config)
 {
     PyObject *dict = PyDict_New();
     if (dict == NULL) {
@@ -936,6 +1004,7 @@ config_as_dict(const PyConfig *config)
     SET_ITEM_WSTRLIST(warnoptions);
     SET_ITEM_WSTR(pythonpath_env);
     SET_ITEM_WSTR(home);
+    SET_ITEM_INT(module_search_paths_set);
     SET_ITEM_WSTRLIST(module_search_paths);
     SET_ITEM_WSTR(executable);
     SET_ITEM_WSTR(base_executable);
@@ -987,6 +1056,285 @@ fail:
 }
 
 
+static PyObject*
+config_dict_get(PyObject *dict, const char *name)
+{
+    PyObject *item = PyDict_GetItemString(dict, name);
+    if (item == NULL) {
+        PyErr_Format(PyExc_ValueError, "missing config key: %s", name);
+        return NULL;
+    }
+    return item;
+}
+
+
+static void
+config_dict_invalid_value(const char *name)
+{
+    PyErr_Format(PyExc_ValueError, "invalid config value: %s", name);
+}
+
+
+static void
+config_dict_invalid_type(const char *name)
+{
+    PyErr_Format(PyExc_TypeError, "invalid config type: %s", name);
+}
+
+
+static int
+config_dict_get_int(PyObject *dict, const char *name, int *result)
+{
+    PyObject *item = config_dict_get(dict, name);
+    if (item == NULL) {
+        return -1;
+    }
+    int value = _PyLong_AsInt(item);
+    if (value == -1 && PyErr_Occurred()) {
+        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
+            config_dict_invalid_type(name);
+        }
+        else {
+            config_dict_invalid_value(name);
+        }
+        return -1;
+    }
+    *result = value;
+    return 0;
+}
+
+
+static int
+config_dict_get_ulong(PyObject *dict, const char *name, unsigned long *result)
+{
+    PyObject *item = config_dict_get(dict, name);
+    if (item == NULL) {
+        return -1;
+    }
+    unsigned long value = PyLong_AsUnsignedLong(item);
+    if (value == (unsigned long)-1 && PyErr_Occurred()) {
+        config_dict_invalid_value(name);
+        return -1;
+    }
+    *result = value;
+    return 0;
+}
+
+
+static int
+config_dict_get_wstr(PyObject *dict, const char *name, PyConfig *config,
+                     wchar_t **result)
+{
+    PyObject *item = config_dict_get(dict, name);
+    if (item == NULL) {
+        return -1;
+    }
+    PyStatus status;
+    if (item == Py_None) {
+        status = PyConfig_SetString(config, result, NULL);
+    }
+    else if (!PyUnicode_Check(item)) {
+        config_dict_invalid_type(name);
+        return -1;
+    }
+    else {
+        wchar_t *wstr = PyUnicode_AsWideCharString(item, NULL);
+        if (wstr == NULL) {
+            return -1;
+        }
+        status = PyConfig_SetString(config, result, wstr);
+        PyMem_Free(wstr);
+    }
+    if (_PyStatus_EXCEPTION(status)) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    return 0;
+}
+
+
+static int
+config_dict_get_wstrlist(PyObject *dict, const char *name, PyConfig *config,
+                         PyWideStringList *result)
+{
+    PyObject *list = config_dict_get(dict, name);
+    if (list == NULL) {
+        return -1;
+    }
+
+    if (!PyList_CheckExact(list)) {
+        config_dict_invalid_type(name);
+        return -1;
+    }
+
+    PyWideStringList wstrlist = _PyWideStringList_INIT;
+    for (Py_ssize_t i=0; i < PyList_GET_SIZE(list); i++) {
+        PyObject *item = PyList_GET_ITEM(list, i);
+
+        if (item == Py_None) {
+            config_dict_invalid_value(name);
+            goto error;
+        }
+        else if (!PyUnicode_Check(item)) {
+            config_dict_invalid_type(name);
+            goto error;
+        }
+        wchar_t *wstr = PyUnicode_AsWideCharString(item, NULL);
+        if (wstr == NULL) {
+            goto error;
+        }
+        PyStatus status = PyWideStringList_Append(&wstrlist, wstr);
+        PyMem_Free(wstr);
+        if (_PyStatus_EXCEPTION(status)) {
+            PyErr_NoMemory();
+            goto error;
+        }
+    }
+
+    if (_PyWideStringList_Copy(result, &wstrlist) < 0) {
+        PyErr_NoMemory();
+        goto error;
+    }
+    _PyWideStringList_Clear(&wstrlist);
+    return 0;
+
+error:
+    _PyWideStringList_Clear(&wstrlist);
+    return -1;
+}
+
+
+int
+_PyConfig_FromDict(PyConfig *config, PyObject *dict)
+{
+    if (!PyDict_Check(dict)) {
+        PyErr_SetString(PyExc_TypeError, "dict expected");
+        return -1;
+    }
+
+#define CHECK_VALUE(NAME, TEST) \
+    if (!(TEST)) { \
+        config_dict_invalid_value(NAME); \
+        return -1; \
+    }
+#define GET_UINT(KEY) \
+    do { \
+        if (config_dict_get_int(dict, #KEY, &config->KEY) < 0) { \
+            return -1; \
+        } \
+        CHECK_VALUE(#KEY, config->KEY >= 0); \
+    } while (0)
+#define GET_WSTR(KEY) \
+    do { \
+        if (config_dict_get_wstr(dict, #KEY, config, &config->KEY) < 0) { \
+            return -1; \
+        } \
+        CHECK_VALUE(#KEY, config->KEY != NULL); \
+    } while (0)
+#define GET_WSTR_OPT(KEY) \
+    do { \
+        if (config_dict_get_wstr(dict, #KEY, config, &config->KEY) < 0) { \
+            return -1; \
+        } \
+    } while (0)
+#define GET_WSTRLIST(KEY) \
+    do { \
+        if (config_dict_get_wstrlist(dict, #KEY, config, &config->KEY) < 0) { \
+            return -1; \
+        } \
+    } while (0)
+
+    GET_UINT(_config_init);
+    CHECK_VALUE("_config_init",
+                config->_config_init == _PyConfig_INIT_COMPAT
+                || config->_config_init == _PyConfig_INIT_PYTHON
+                || config->_config_init == _PyConfig_INIT_ISOLATED);
+    GET_UINT(isolated);
+    GET_UINT(use_environment);
+    GET_UINT(dev_mode);
+    GET_UINT(install_signal_handlers);
+    GET_UINT(use_hash_seed);
+    if (config_dict_get_ulong(dict, "hash_seed", &config->hash_seed) < 0) {
+        return -1;
+    }
+    CHECK_VALUE("hash_seed", config->hash_seed <= MAX_HASH_SEED);
+    GET_UINT(faulthandler);
+    GET_UINT(tracemalloc);
+    GET_UINT(import_time);
+    GET_UINT(show_ref_count);
+    GET_UINT(dump_refs);
+    GET_UINT(malloc_stats);
+    GET_WSTR(filesystem_encoding);
+    GET_WSTR(filesystem_errors);
+    GET_WSTR_OPT(pycache_prefix);
+    GET_UINT(parse_argv);
+    GET_WSTRLIST(orig_argv);
+    GET_WSTRLIST(argv);
+    GET_WSTRLIST(xoptions);
+    GET_WSTRLIST(warnoptions);
+    GET_UINT(site_import);
+    GET_UINT(bytes_warning);
+    GET_UINT(inspect);
+    GET_UINT(interactive);
+    GET_UINT(optimization_level);
+    GET_UINT(parser_debug);
+    GET_UINT(write_bytecode);
+    GET_UINT(verbose);
+    GET_UINT(quiet);
+    GET_UINT(user_site_directory);
+    GET_UINT(configure_c_stdio);
+    GET_UINT(buffered_stdio);
+    GET_WSTR(stdio_encoding);
+    GET_WSTR(stdio_errors);
+#ifdef MS_WINDOWS
+    GET_UINT(legacy_windows_stdio);
+#endif
+    GET_WSTR(check_hash_pycs_mode);
+
+    GET_UINT(pathconfig_warnings);
+    GET_WSTR(program_name);
+    GET_WSTR_OPT(pythonpath_env);
+    GET_WSTR_OPT(home);
+    GET_WSTR(platlibdir);
+
+    GET_UINT(module_search_paths_set);
+    GET_WSTRLIST(module_search_paths);
+    if (config->_install_importlib) {
+        GET_WSTR(executable);
+        GET_WSTR(base_executable);
+        GET_WSTR(prefix);
+        GET_WSTR(base_prefix);
+        GET_WSTR(exec_prefix);
+        GET_WSTR(base_exec_prefix);
+    }
+    else {
+        GET_WSTR_OPT(executable);
+        GET_WSTR_OPT(base_executable);
+        GET_WSTR_OPT(prefix);
+        GET_WSTR_OPT(base_prefix);
+        GET_WSTR_OPT(exec_prefix);
+        GET_WSTR_OPT(base_exec_prefix);
+    }
+
+    GET_UINT(skip_source_first_line);
+    GET_WSTR_OPT(run_command);
+    GET_WSTR_OPT(run_module);
+    GET_WSTR_OPT(run_filename);
+
+    GET_UINT(_install_importlib);
+    GET_UINT(_init_main);
+    GET_UINT(_isolated_interpreter);
+
+    assert(config_check_consistency(config));
+
+#undef CHECK_VALUE
+#undef GET_UINT
+#undef GET_WSTR
+#undef GET_WSTR_OPT
+    return 0;
+}
+
+
 static const char*
 config_get_env(const PyConfig *config, const char *name)
 {
@@ -1254,7 +1602,6 @@ config_init_home(PyConfig *config)
                               L"PYTHONHOME", "PYTHONHOME");
 }
 
-
 static PyStatus
 config_init_hash_seed(PyConfig *config)
 {
@@ -1268,7 +1615,7 @@ config_init_hash_seed(PyConfig *config)
         errno = 0;
         seed = strtoul(seed_text, (char **)&endptr, 10);
         if (*endptr != '\0'
-            || seed > 4294967295UL
+            || seed > MAX_HASH_SEED
             || (errno == ERANGE && seed == ULONG_MAX))
         {
             return _PyStatus_ERR("PYTHONHASHSEED must be \"random\" "
@@ -2532,58 +2879,7 @@ PyConfig_Read(PyConfig *config)
         goto done;
     }
 
-    /* Check config consistency */
-    assert(config->isolated >= 0);
-    assert(config->use_environment >= 0);
-    assert(config->dev_mode >= 0);
-    assert(config->install_signal_handlers >= 0);
-    assert(config->use_hash_seed >= 0);
-    assert(config->faulthandler >= 0);
-    assert(config->tracemalloc >= 0);
-    assert(config->site_import >= 0);
-    assert(config->bytes_warning >= 0);
-    assert(config->inspect >= 0);
-    assert(config->interactive >= 0);
-    assert(config->optimization_level >= 0);
-    assert(config->parser_debug >= 0);
-    assert(config->write_bytecode >= 0);
-    assert(config->verbose >= 0);
-    assert(config->quiet >= 0);
-    assert(config->user_site_directory >= 0);
-    assert(config->parse_argv >= 0);
-    assert(config->configure_c_stdio >= 0);
-    assert(config->buffered_stdio >= 0);
-    assert(config->program_name != NULL);
-    assert(_PyWideStringList_CheckConsistency(&config->argv));
-    /* sys.argv must be non-empty: empty argv is replaced with [''] */
-    assert(config->argv.length >= 1);
-    assert(_PyWideStringList_CheckConsistency(&config->xoptions));
-    assert(_PyWideStringList_CheckConsistency(&config->warnoptions));
-    assert(_PyWideStringList_CheckConsistency(&config->module_search_paths));
-    if (config->_install_importlib) {
-        assert(config->module_search_paths_set != 0);
-        /* don't check config->module_search_paths */
-        assert(config->executable != NULL);
-        assert(config->base_executable != NULL);
-        assert(config->prefix != NULL);
-        assert(config->base_prefix != NULL);
-        assert(config->exec_prefix != NULL);
-        assert(config->base_exec_prefix != NULL);
-    }
-    assert(config->platlibdir != NULL);
-    assert(config->filesystem_encoding != NULL);
-    assert(config->filesystem_errors != NULL);
-    assert(config->stdio_encoding != NULL);
-    assert(config->stdio_errors != NULL);
-#ifdef MS_WINDOWS
-    assert(config->legacy_windows_stdio >= 0);
-#endif
-    /* -c and -m options are exclusive */
-    assert(!(config->run_command != NULL && config->run_module != NULL));
-    assert(config->check_hash_pycs_mode != NULL);
-    assert(config->_install_importlib >= 0);
-    assert(config->pathconfig_warnings >= 0);
-    assert(_PyWideStringList_CheckConsistency(&config->orig_argv));
+    assert(config_check_consistency(config));
 
     status = _PyStatus_OK();
 
@@ -2628,7 +2924,7 @@ _Py_GetConfigsAsDict(void)
 
     /* core config */
     const PyConfig *config = _PyInterpreterState_GetConfig(tstate->interp);
-    dict = config_as_dict(config);
+    dict = _PyConfig_AsDict(config);
     if (dict == NULL) {
         goto error;
     }
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 60b2494..ae4f0ee 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -2922,7 +2922,9 @@ _PySys_UpdateConfig(PyThreadState *tstate)
 #define SET_SYS_FROM_WSTR(KEY, VALUE) \
         SET_SYS(KEY, PyUnicode_FromWideChar(VALUE, -1));
 
-    COPY_LIST("path", config->module_search_paths);
+    if (config->module_search_paths_set) {
+        COPY_LIST("path", config->module_search_paths);
+    }
 
     SET_SYS_FROM_WSTR("executable", config->executable);
     SET_SYS_FROM_WSTR("_base_executable", config->base_executable);