Add valid_identifier_{pve,pvn,sv} API functions

These functions test whether a given string would be considered by the
Perl parser to be a valid identifier. Three variants are provided: one
taking a string start/end pair, one a string start/length pair, and one
looking at the string contained in an SV.

MANIFEST

@@ -5207,6 +5207,7 @@ ext/XS-APItest/t/utf8_warn07.t			Tests for code in utf8.c
 ext/XS-APItest/t/utf8_warn08.t			Tests for code in utf8.c
 ext/XS-APItest/t/utf8_warn09.t			Tests for code in utf8.c
 ext/XS-APItest/t/utf8_warn_base.pl		Tests for code in utf8.c
+ext/XS-APItest/t/valid_identifier.t		XS::APItest: tests for valid_identifier_sv()
 ext/XS-APItest/t/weaken.t			XS::APItest: tests for sv_rvweaken() and sv_get_backrefs()
 ext/XS-APItest/t/whichsig.t			XS::APItest: tests for whichsig() and variants
 ext/XS-APItest/t/win32.t			Test Win32 specific APIs

embed.fnc

@@ -3766,6 +3766,16 @@ EXdpx	|bool	|validate_proto |NN SV *name				\
 				|NULLOK SV *proto			\
 				|bool warn				\
 				|bool curstash
+Adp	|bool	|valid_identifier_pve					\
+				|NN const char *s			\
+				|NN const char *end			\
+				|U32 flags
+Adp	|bool	|valid_identifier_pvn					\
+				|NN const char *s			\
+				|STRLEN len				\
+				|U32 flags
+Adp	|bool	|valid_identifier_sv					\
+				|NULLOK SV *sv
 CRTdip	|UV	|valid_utf8_to_uvchr					\
 				|NN const U8 *s 			\
 				|NULLOK STRLEN *retlen

embed.h

@@ -865,6 +865,9 @@
 # define uvchr_to_utf8_flags(a,b,c)             Perl_uvchr_to_utf8_flags(aTHX,a,b,c)
 # define uvchr_to_utf8_flags_msgs(a,b,c,d)      Perl_uvchr_to_utf8_flags_msgs(aTHX,a,b,c,d)
 # define uvoffuni_to_utf8_flags_msgs(a,b,c,d)   Perl_uvoffuni_to_utf8_flags_msgs(aTHX_ a,b,c,d)
+# define valid_identifier_pve(a,b,c)            Perl_valid_identifier_pve(aTHX_ a,b,c)
+# define valid_identifier_pvn(a,b,c)            Perl_valid_identifier_pvn(aTHX_ a,b,c)
+# define valid_identifier_sv(a)                 Perl_valid_identifier_sv(aTHX_ a)
 # define valid_utf8_to_uvchr                    Perl_valid_utf8_to_uvchr
 # define vcmp(a,b)                              Perl_vcmp(aTHX_ a,b)
 # define vcroak(a,b)                            Perl_vcroak(aTHX_ a,b)

ext/XS-APItest/APItest.pm

@@ -4,7 +4,7 @@ use strict;
 use warnings;
 use Carp;
 
-our $VERSION = '1.39';
+our $VERSION = '1.40';
 
 require XSLoader;
 

ext/XS-APItest/APItest.xs

@@ -7408,6 +7408,12 @@ gimme()
     OUTPUT:
         RETVAL
 
+bool
+valid_identifier(SV *s)
+    CODE:
+        RETVAL = valid_identifier_sv(s);
+    OUTPUT:
+        RETVAL
 
 MODULE = XS::APItest            PACKAGE = XS::APItest::Backrefs
 

ext/XS-APItest/t/valid_identifier.t

@@ -0,0 +1,43 @@
+#!perl
+
+use strict;
+use warnings;
+
+use open ':std', ':encoding(UTF-8)';
+use Test::More;
+
+use_ok('XS::APItest');
+
+# These should all be valid
+foreach my $id (qw( abc ab_cd _abc x123 )) {
+    ok(valid_identifier($id), "'$id' is valid identifier");
+}
+
+# These should all not be
+foreach my $id (qw( ab-cd 123 abc() ), "ab cd") {
+    ok(!valid_identifier($id), "'$id' is not valid identifier");
+}
+
+# Now for some UTF-8 tests
+{
+    use utf8;
+
+    foreach my $id (qw( café sandviĉon )) {
+        ok(valid_identifier($id), "'$id' is valid UTF-8 identifier");
+    }
+
+    # en-dash
+    ok(!valid_identifier("ab–cd"), "'ab–cd' is not valid UTF-8 identifier");
+}
+
+# objects with "" overloading still work
+{
+    package WithStringify {
+        use overload '""' => sub { return "an_identifier"; };
+        sub new { bless [], shift; }
+    }
+
+    ok(valid_identifier(WithStringify->new), 'Object with stringify overload can be valid identifier');
+}
+
+done_testing;

pod/perldelta.pod

@@ -350,6 +350,13 @@ well.
 
 XXX
 
+=item *
+
+New API functions L<C<valid_identifier_pve()>|perlapi/valid_identifier_pve>,
+L<C<valid_identifier_pvn()>|perlapi/valid_identifier_pvn> and
+L<C<valid_identifier_sv()>|perlapi/valid_identifier_sv> have been added, which
+test if a string would be considered by Perl to be a valid identifier name.
+
 =back
 
 =head1 Selected Bug Fixes

toke.c

@@ -13932,6 +13932,105 @@ Perl_parse_subsignature(pTHX_ U32 flags)
     return parse_recdescent_for_op(GRAMSUBSIGNATURE, LEX_FAKEEOF_NONEXPR);
 }
 
+/*
+=for apidoc valid_identifier_pve
+
+Returns true if the string given by C<s> until C<end> would be considered
+valid as a Perl identifier.  That is, it must begin with a character matching
+C<isIDFIRST>, followed by characters all matching C<isIDCONT>.  An empty
+string (i.e. when C<end> is C<s>) will return false.
+
+If C<flags> contains the C<SVf_UTF8> bit, then the string is presumed to be
+encoded in UTF-8, and suitable Unicode character test functions will be used.
+
+=cut
+*/
+
+bool
+Perl_valid_identifier_pve(pTHX_ const char *s, const char *end, U32 flags)
+{
+    PERL_ARGS_ASSERT_VALID_IDENTIFIER_PVE;
+
+    if(end <= s)
+        return false;
+
+    if(flags & SVf_UTF8) {
+        if(!isIDFIRST_utf8_safe((U8 *)s, (U8 *)end))
+            return false;
+
+        while(s < end) {
+            s += UTF8SKIP((U8 *)s);
+            if(s == end)
+                break;
+            if(!isIDCONT_utf8_safe((U8 *)s, (U8 *)end))
+                return false;
+        }
+        return true;
+    }
+    else {
+        if(!isIDFIRST(s[0]))
+            return false;
+
+        while(s < end) {
+            s += 1;
+            if(s == end)
+                break;
+            if(!isIDCONT(s[0]))
+                return false;
+        }
+        return true;
+    }
+
+    return false;
+}
+
+/*
+=for apidoc valid_identifier_pvn
+
+Returns true if the string given by C<s> whose length is C<len> would be
+considered valid as a Perl identifier.  That is, it must begin with a
+character matching C<isIDFIRST>, followed by characters all matching
+C<isIDCONT>.  An empty string (i.e. when C<len> is zero) will return false.
+
+If C<flags> contains the C<SVf_UTF8> bit, then the string is presumed to be
+encoded in UTF-8, and suitable Unicode character test functions will be used.
+
+=cut
+*/
+
+bool
+Perl_valid_identifier_pvn(pTHX_ const char *s, STRLEN len, U32 flags)
+{
+    PERL_ARGS_ASSERT_VALID_IDENTIFIER_PVN;
+
+    return valid_identifier_pve(s, s + len, flags);
+}
+
+/*
+=for apidoc valid_identifier_sv
+
+Returns true if the given SV contains a non-empty string whose characters
+match accoding to C<valid_identifier_pvn>.  Returns false if given NULL, an
+undefined SV, or a SV that does not contain a non-empty string.
+
+Does not invoke C<get> magic on the SV beforehand.
+
+=cut
+*/
+
+bool
+Perl_valid_identifier_sv(pTHX_ SV *sv)
+{
+    PERL_ARGS_ASSERT_VALID_IDENTIFIER_SV;
+
+    if(!sv || !SvOK(sv))
+        return false;
+
+    STRLEN len;
+    const char *pv = SvPV_const(sv, len);
+    return valid_identifier_pve(pv, pv + len, SvUTF8(sv));
+}
+
 /*
  * ex: set ts=8 sts=4 sw=4 et:
  */