gh-158001: Avoid deprecated variable in Py_GETENV() (#158003)

No longer use deprecated Py_IgnoreEnvironmentFlag in Py_GETENV().
Instead, use PyConfig.use_environment when Python is initialized.

Modify also PySys_SetArgv() to use PyConfig.isolated when Python is
initialized.

Lib/test/test_embed.py

@@ -2114,6 +2114,10 @@ class AuditingTests(EmbeddingTestsMixin, unittest.TestCase):
     def test_concurrent_finalization_stress(self):
         self.run_embedded_interpreter("test_concurrent_finalization_stress")
 
+    def test_py_getenv(self):
+        # Test Py_GETENV() before init, when initialized, and after finalize
+        self.run_embedded_interpreter("test_py_getenv")
+
 
 class MiscTests(EmbeddingTestsMixin, unittest.TestCase):
     def test_unicode_id_init(self):

Programs/_testembed.c

@@ -2357,6 +2357,43 @@ static int test_isinitialized_false_during_site_import(void)
 }
 
 
+static int test_py_getenv(void)
+{
+    const char *name = "PYTHON_TESTEMBED_VARIABLE";
+    const char *expected = "expected_value";
+    putenv("PYTHON_TESTEMBED_VARIABLE=expected_value");
+
+    const char *var = Py_GETENV(name);
+    if (var == NULL || strcmp(var, expected) != 0) {
+        error_fmt("%s is not set before Python initialization", name);
+        return 1;
+    }
+
+    // Initialize Python with use_environment=0
+    PyConfig config;
+    _PyConfig_InitCompatConfig(&config);
+    config_set_program_name(&config);
+    config.use_environment = 0;
+    init_from_config_clear(&config);
+
+    var = Py_GETENV(name);
+    if (var != NULL) {
+        error_fmt("Py_GETENV() doesn't ignore %s after Python init", name);
+        return 1;
+    }
+
+    Py_Finalize();
+    var = Py_GETENV(name);
+    if (var == NULL || strcmp(var, expected) != 0) {
+        error_fmt("%s is not set after Python finalization", name);
+        return 1;
+    }
+
+    printf("OK\n");
+    return 0;
+}
+
+
 #ifndef MS_WINDOWS
 #include "test_frozenmain.h"      // M_test_frozenmain
 
@@ -3059,6 +3096,7 @@ static struct TestCase TestCases[] = {
     {"test_init_main_interpreter_settings", test_init_main_interpreter_settings},
     {"test_init_in_background_thread", test_init_in_background_thread},
     {"test_isinitialized_false_during_site_import", test_isinitialized_false_during_site_import},
+    {"test_py_getenv", test_py_getenv},
 
     // Audit
     {"test_open_code_hook", test_open_code_hook},

Python/initconfig.c

@@ -712,13 +712,17 @@ _Py_COMP_DIAG_POP
 char*
 Py_GETENV(const char *name)
 {
-_Py_COMP_DIAG_PUSH
-_Py_COMP_DIAG_IGNORE_DEPR_DECLS
-    if (Py_IgnoreEnvironmentFlag) {
+    int use_environment = 1;
+    PyThreadState *tstate = PyThreadState_GetUnchecked();
+    if (tstate != NULL) {
+        const PyConfig *config = &tstate->interp->config;
+        use_environment = config->use_environment;
+    }
+
+    if (!use_environment) {
         return NULL;
     }
     return getenv(name);
-_Py_COMP_DIAG_POP
 }
 
 /* --- PyStatus ----------------------------------------------- */

Python/sysmodule.c

@@ -4540,9 +4540,16 @@ PySys_SetArgvEx(int argc, wchar_t **argv, int updatepath)
 void
 PySys_SetArgv(int argc, wchar_t **argv)
 {
+    int isolated = 0;
+    PyThreadState *tstate = PyThreadState_GetUnchecked();
+    if (tstate != NULL) {
+        const PyConfig *config = &tstate->interp->config;
+        isolated = config->isolated;
+    }
+
 _Py_COMP_DIAG_PUSH
 _Py_COMP_DIAG_IGNORE_DEPR_DECLS
-    PySys_SetArgvEx(argc, argv, Py_IsolatedFlag == 0);
+    PySys_SetArgvEx(argc, argv, isolated == 0);
 _Py_COMP_DIAG_POP
 }