bpo-40334: Support CO_FUTURE_BARRY_AS_BDFL in the new parser (GH-19721)

This commit also allows to pass flags to the new parser in all interfaces and fixes a bug in the parser generator that was causing to inline rules with actions, making them disappear.
diff --git a/Parser/pegen/pegen.c b/Parser/pegen/pegen.c
index c8f5c95..081da82 100644
--- a/Parser/pegen/pegen.c
+++ b/Parser/pegen/pegen.c
@@ -25,6 +25,24 @@
     return 1;
 }
 
+/* Checks if the NOTEQUAL token is valid given the current parser flags
+0 indicates success and nonzero indicates failure (an exception may be set) */
+int
+_PyPegen_check_barry_as_flufl(Parser *p) {
+    Token *t = p->tokens[p->fill - 1];
+    assert(t->bytes != NULL);
+    assert(t->type == NOTEQUAL);
+
+    char* tok_str = PyBytes_AS_STRING(t->bytes);
+    if (p->flags & PyPARSE_BARRY_AS_BDFL && strcmp(tok_str, "<>")){
+        RAISE_SYNTAX_ERROR("with Barry as BDFL, use '<>' instead of '!='");
+        return -1;
+    } else if (!(p->flags & PyPARSE_BARRY_AS_BDFL)) {
+        return strcmp(tok_str, "!=");
+    }
+    return 0;
+}
+
 PyObject *
 _PyPegen_new_identifier(Parser *p, char *n)
 {
@@ -401,7 +419,6 @@
         loc = Py_None;
     }
 
-
     tmp = Py_BuildValue("(OiiN)", p->tok->filename, t->lineno, col_number, loc);
     if (!tmp) {
         goto error;
@@ -902,8 +919,31 @@
     PyMem_Free(p);
 }
 
+static int
+compute_parser_flags(PyCompilerFlags *flags)
+{
+    int parser_flags = 0;
+    if (!flags) {
+        return 0;
+    }
+    if (flags->cf_flags & PyCF_DONT_IMPLY_DEDENT) {
+        parser_flags |= PyPARSE_DONT_IMPLY_DEDENT;
+    }
+    if (flags->cf_flags & PyCF_IGNORE_COOKIE) {
+        parser_flags |= PyPARSE_IGNORE_COOKIE;
+    }
+    if (flags->cf_flags & CO_FUTURE_BARRY_AS_BDFL) {
+        parser_flags |= PyPARSE_BARRY_AS_BDFL;
+    }
+    if (flags->cf_flags & PyCF_TYPE_COMMENTS) {
+        parser_flags |= PyPARSE_TYPE_COMMENTS;
+    }
+    return parser_flags;
+}
+
 Parser *
-_PyPegen_Parser_New(struct tok_state *tok, int start_rule, int *errcode, PyArena *arena)
+_PyPegen_Parser_New(struct tok_state *tok, int start_rule, int flags,
+                    int *errcode, PyArena *arena)
 {
     Parser *p = PyMem_Malloc(sizeof(Parser));
     if (p == NULL) {
@@ -938,6 +978,7 @@
 
     p->starting_lineno = 0;
     p->starting_col_offset = 0;
+    p->flags = flags;
 
     return p;
 }
@@ -976,7 +1017,7 @@
 mod_ty
 _PyPegen_run_parser_from_file_pointer(FILE *fp, int start_rule, PyObject *filename_ob,
                              const char *enc, const char *ps1, const char *ps2,
-                             int *errcode, PyArena *arena)
+                             PyCompilerFlags *flags, int *errcode, PyArena *arena)
 {
     struct tok_state *tok = PyTokenizer_FromFile(fp, enc, ps1, ps2);
     if (tok == NULL) {
@@ -993,7 +1034,8 @@
     // From here on we need to clean up even if there's an error
     mod_ty result = NULL;
 
-    Parser *p = _PyPegen_Parser_New(tok, start_rule, errcode, arena);
+    int parser_flags = compute_parser_flags(flags);
+    Parser *p = _PyPegen_Parser_New(tok, start_rule, parser_flags, errcode, arena);
     if (p == NULL) {
         goto error;
     }
@@ -1008,7 +1050,7 @@
 
 mod_ty
 _PyPegen_run_parser_from_file(const char *filename, int start_rule,
-                     PyObject *filename_ob, PyArena *arena)
+                     PyObject *filename_ob, PyCompilerFlags *flags, PyArena *arena)
 {
     FILE *fp = fopen(filename, "rb");
     if (fp == NULL) {
@@ -1017,7 +1059,7 @@
     }
 
     mod_ty result = _PyPegen_run_parser_from_file_pointer(fp, start_rule, filename_ob,
-                                                 NULL, NULL, NULL, NULL, arena);
+                                                 NULL, NULL, NULL, flags, NULL, arena);
 
     fclose(fp);
     return result;
@@ -1025,12 +1067,12 @@
 
 mod_ty
 _PyPegen_run_parser_from_string(const char *str, int start_rule, PyObject *filename_ob,
-                       int iflags, PyArena *arena)
+                       PyCompilerFlags *flags, PyArena *arena)
 {
     int exec_input = start_rule == Py_file_input;
 
     struct tok_state *tok;
-    if (iflags & PyCF_IGNORE_COOKIE) {
+    if (flags == NULL || flags->cf_flags & PyCF_IGNORE_COOKIE) {
         tok = PyTokenizer_FromUTF8(str, exec_input);
     } else {
         tok = PyTokenizer_FromString(str, exec_input);
@@ -1048,7 +1090,8 @@
     // We need to clear up from here on
     mod_ty result = NULL;
 
-    Parser *p = _PyPegen_Parser_New(tok, start_rule, NULL, arena);
+    int parser_flags = compute_parser_flags(flags);
+    Parser *p = _PyPegen_Parser_New(tok, start_rule, parser_flags, NULL, arena);
     if (p == NULL) {
         goto error;
     }