Made self and parent their own grammar nodes

[wu-s-john]

This is a PR that helps solves the issue, PHP, not recognizing const variables as constant strings

• In php, self and parent are used to get particular information of a class. Self is used to help get static information of a class and parent is used to get information of the supertype of an object. It would be nice to exhibit these behaviors for semgrep. This information is useful to constant propogation. To make this more apparent, it would be helpful to have these nodes represented in the php CST. These fields represented in CST_php.class_scope_resolution_ident.
• Self and Parent are now special identifiers in the php_ast
• Essentially, self seems to be only used as identifiers in expressions and as type annotations in php. This change helps accomodate for that.

The corresponding semgrep changes are made here. https://github.com/returntocorp/semgrep/pull/5022

Security

• [x] Change has no security implications (otherwise, ping the security team)

[IagoAbal]

I don't know much about PHP (maybe @nmote know some PHP?), but overall it looks good to me! Could you take a look at my comments? Thanks for contributing!

[wu-s-john]

@aryx

Here is the test plan and the parsing stats affected by my PR.

In the end, the changes to the parsing code was very slight. You can see the changes below where the expression self is translated to IdSpecial((Self, ())

Test Plan

$ cat  semgrep-core/tests/php/constant_propogation.php
<?php

class Example
{
    const CMD = 'This is an constant.';

    public function someMethod()
    {
        // ERROR:
        exec(self::CMD);
    }
}

$ pfff -dump_php semgrep-core/tests/php/constant_propogation.php #cst_php
[(ClassDef
    { c_attrs = None; c_type = (ClassRegular ());
      c_name = (Name ("Example", ())); c_tparams = None; c_extends = None;
      c_implements = None; c_enum_type = None;
      c_body =
      ((),
       [(ClassConstants ([], (), None,
           [(Left
               ((Name ("CMD", ())),
                ((), (Sc (C (String ("This is an constant.", ())))))))
             ],
           ()));
         (Method
            { f_attrs = None; f_tok = (); f_type = MethodRegular;
              f_modifiers = [(Public, ())]; f_ref = None;
              f_name = (Name ("someMethod", ())); f_tparams = None;
              f_params = ((), [], ()); f_return_type = None;
              f_body =
              ((),
               [(ExprStmt (
                   (Call ((Id (XName [(QI (Name ("exec", ())))])),
                      ((),
                       [(Left
                           (Arg
                              (ClassGet ((Id (Self ())), (),
                                 (Id (XName [(QI (Name ("CMD", ())))]))))))
                         ],
                       ())
                      )),
                   ()))
                 ],
               ())
              })
         ],
       ())
      });
  (FinalDef ())]

$ semgrep-core -dump_pfff_ast -lang php semgrep-core/tests/php/constant_propogation.php #ast_php
Pr(
  [DefStmt(
     ({
       name=EN(
              Id(("Example", ()),
                {id_info_id=5; id_hidden=false; id_resolved=Ref(None); 
                 id_type=Ref(None); id_svalue=Ref(None); }));
       attrs=[]; tparams=[]; },
      ClassDef(
        {ckind=(Class, ()); cextends=[]; cimplements=[]; cmixins=[]; 
         cparams=[]; 
         cbody=[F(
                  DefStmt(
                    ({
                      name=EN(
                             Id(("CMD", ()),
                               {id_info_id=1; id_hidden=false; 
                                id_resolved=Ref(None); id_type=Ref(None); 
                                id_svalue=Ref(None); }));
                      attrs=[KeywordAttr((Const, ()))]; tparams=[]; },
                     VarDef(
                       {vinit=Some(L(String(("This is an constant.", ())))); 
                        vtype=None; }))));
                F(
                  DefStmt(
                    ({
                      name=EN(
                             Id(("someMethod", ()),
                               {id_info_id=4; id_hidden=false; 
                                id_resolved=Ref(None); id_type=Ref(None); 
                                id_svalue=Ref(None); }));
                      attrs=[KeywordAttr((Public, ()))]; tparams=[]; },
                     FuncDef(
                       {fkind=(Method, ()); fparams=[]; frettype=None; 
                        fbody=FBStmt(
                                Block(
                                  [ExprStmt(
                                     Call(
                                       N(
                                         Id(("exec", ()),
                                           {id_info_id=2; id_hidden=false; 
                                            id_resolved=Ref(None); 
                                            id_type=Ref(None); 
                                            id_svalue=Ref(None); })),
                                       [Arg(
                                          DotAccess(IdSpecial((Self, ())),
                                            (),
                                            FN(
                                              Id(("CMD", ()),
                                                {id_info_id=3; 
                                                 id_hidden=false; 
                                                 id_resolved=Ref(None); 
                                                 id_type=Ref(None); 
                                                 id_svalue=Ref(None); }))))]),
                                     ())]));
                        }))))];
         })))])

Stats

stats before PR change:

lang/php/stats.json:3
   "global": {
     "name": "*",
     "parsing_rate": 0.8984308332917063,
     "line_count": 5305045,
     "error_line_count": 538829,
     "file_count": 35023,
     "error_file_count": 1498
   },

stats after PR change:

lang/php/stats.json:3
   "global": {
     "name": "*",
     "parsing_rate": 0.8984308332917063,
     "line_count": 5305045,
     "error_line_count": 538829,
     "file_count": 35023,
     "error_file_count": 1498
   },

Overall, doesn't look like anything change

[wu-s-john]

@IagoAbal @aryx

Thanks for the suggestions. I incorporated your feedback. Please take a look again when you have time.

[aryx]

not sure what's going on with circleci not running

[wu-s-john]

@aryx

Thanks for merging the PR.