bpo-45019: Do some cleanup related to frozen modules. (gh-28319)

There are a few things I missed in gh-27980. This is a follow-up that will make subsequent PRs cleaner. It includes fixes to tests and tools that reference the frozen modules.

https://bugs.python.org/issue45019

Python/clinic/import.c.h

@@ -297,6 +297,24 @@ exit:
     return return_value;
 }
 
+PyDoc_STRVAR(_imp__frozen_module_names__doc__,
+"_frozen_module_names($module, /)\n"
+"--\n"
+"\n"
+"Returns the list of available frozen modules.");
+
+#define _IMP__FROZEN_MODULE_NAMES_METHODDEF    \
+    {"_frozen_module_names", (PyCFunction)_imp__frozen_module_names, METH_NOARGS, _imp__frozen_module_names__doc__},
+
+static PyObject *
+_imp__frozen_module_names_impl(PyObject *module);
+
+static PyObject *
+_imp__frozen_module_names(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+    return _imp__frozen_module_names_impl(module);
+}
+
 #if defined(HAVE_DYNAMIC_LOADING)
 
 PyDoc_STRVAR(_imp_create_dynamic__doc__,
@@ -449,4 +467,4 @@ exit:
 #ifndef _IMP_EXEC_DYNAMIC_METHODDEF
     #define _IMP_EXEC_DYNAMIC_METHODDEF
 #endif /* !defined(_IMP_EXEC_DYNAMIC_METHODDEF) */
-/*[clinic end generated code: output=7c31c433af88af6b input=a9049054013a1b77]*/
+/*[clinic end generated code: output=0ab3fa7c5808bba4 input=a9049054013a1b77]*/

Python/frozen.c

@@ -47,7 +47,7 @@
 /* Note that a negative size indicates a package. */
 
 static const struct _frozen _PyImport_FrozenModules[] = {
-    /* importlib */
+    /* import system */
     {"_frozen_importlib", _Py_M__importlib__bootstrap,
         (int)sizeof(_Py_M__importlib__bootstrap)},
     {"_frozen_importlib_external", _Py_M__importlib__bootstrap_external,

Python/frozen_modules/MANIFEST

@@ -0,0 +1,12 @@
+# The list of frozen modules with key information.
+# Note that the "check_generated_files" CI job will identify
+# when source files were changed but regen-frozen wasn't run.
+# This file is auto-generated by Tools/scripts/freeze_modules.py.
+          module           ispkg              source                          frozen               checksum
+-------------------------- ----- ------------------------------- ------------------------------- ------------
+_frozen_importlib            no  <importlib._bootstrap>          importlib__bootstrap.h          749d553f858d
+_frozen_importlib_external   no  <importlib._bootstrap_external> importlib__bootstrap_external.h e4539e6347d7
+zipimport                    no  <zipimport>                     zipimport.h                     374879e5d43d
+__hello__                    no  Tools/freeze/flag.py            hello.h                         af6fb665713f
+__phello__                  YES  Tools/freeze/flag.py            hello.h                         af6fb665713f
+__phello__.spam              no  Tools/freeze/flag.py            hello.h                         af6fb665713f

Python/frozen_modules/README.txt

@@ -0,0 +1,7 @@
+This directory contains the generated .h files for all the frozen
+modules.  Python/frozen.c depends on these files.
+
+Note that, other than the required frozen modules, none of these files
+are committed into the repo.
+
+See Tools/scripts/freeze_modules.py for more info.

Python/import.c

@@ -16,6 +16,7 @@
 #include "code.h"
 #include "importdl.h"
 #include "pydtrace.h"
+#include <stdbool.h>
 
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
@@ -1049,6 +1050,32 @@ _imp_create_builtin(PyObject *module, PyObject *spec)
 
 /* Frozen modules */
 
+static PyObject *
+list_frozen_module_names(bool force)
+{
+    PyObject *names = PyList_New(0);
+    if (names == NULL) {
+        return NULL;
+    }
+    for (const struct _frozen *p = PyImport_FrozenModules; ; p++) {
+        if (p->name == NULL) {
+            break;
+        }
+        PyObject *name = PyUnicode_FromString(p->name);
+        if (name == NULL) {
+            Py_DECREF(names);
+            return NULL;
+        }
+        int res = PyList_Append(names, name);
+        Py_DECREF(name);
+        if (res != 0) {
+            Py_DECREF(names);
+            return NULL;
+        }
+    }
+    return names;
+}
+
 static const struct _frozen *
 find_frozen(PyObject *name)
 {
@@ -1954,6 +1981,19 @@ _imp_is_frozen_impl(PyObject *module, PyObject *name)
     return PyBool_FromLong((long) (p == NULL ? 0 : p->size));
 }
 
+/*[clinic input]
+_imp._frozen_module_names
+
+Returns the list of available frozen modules.
+[clinic start generated code]*/
+
+static PyObject *
+_imp__frozen_module_names_impl(PyObject *module)
+/*[clinic end generated code: output=80609ef6256310a8 input=76237fbfa94460d2]*/
+{
+    return list_frozen_module_names(true);
+}
+
 /* Common implementation for _imp.exec_dynamic and _imp.exec_builtin */
 static int
 exec_builtin_or_dynamic(PyObject *mod) {
@@ -2114,6 +2154,7 @@ static PyMethodDef imp_methods[] = {
     _IMP_INIT_FROZEN_METHODDEF
     _IMP_IS_BUILTIN_METHODDEF
     _IMP_IS_FROZEN_METHODDEF
+    _IMP__FROZEN_MODULE_NAMES_METHODDEF
     _IMP_CREATE_DYNAMIC_METHODDEF
     _IMP_EXEC_DYNAMIC_METHODDEF
     _IMP_EXEC_BUILTIN_METHODDEF