warn if do "somefile" fails when . not default in @INC and somefile exists

the message and warning category may need adjustment

3 files changed, 44 insertions, 4 deletions

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 390ba81e09..9a4cdf6352 100644
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -2061,6 +2061,14 @@ define a C<$VERSION>.
 (F) You cannot put a repeat count of any kind right after the '/' code.
 See L<perlfunc/pack>.
 
+=item do "%s" failed, '.' is no longer in @INC
+
+(W deprecated) Previously C< do "somefile"; > would search the current
+directory for the specified file.  Since F<.> has been removed from
+C<@INC> by default this is no longer true.  To search the current
+directory (and only the current directory) you can write C< do
+"./somefile"; >.
+
 =item Don't know how to get file name
 
 (P) C<PerlIO_getname>, a perl internal I/O function specific to VMS, was
diff --git a/pp_ctl.c b/pp_ctl.c
index ef5b122824..a1262323e5 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -3695,7 +3695,7 @@ S_require_version(pTHX_ SV *sv)
  * the second form */
 
 static OP *
-S_require_file(pTHX_ SV *const sv)
+S_require_file(pTHX_ SV *sv)
 {
     dVAR; dSP;
 
@@ -4104,9 +4104,28 @@ S_require_file(pTHX_ SV *const sv)
 	    }
 	    DIE(aTHX_ "Can't locate %s", name);
 	}
-
-	CLEAR_ERRSV();
-	RETPUSHUNDEF;
+        else {
+#ifdef DEFAULT_INC_EXCLUDES_DOT
+            Stat_t st;
+            PerlIO *io = NULL;
+            dSAVE_ERRNO;
+            /* the complication is to match the logic from doopen_pm() so we don't treat do "sda1" as
+               a previously successful "do".
+            */
+            bool do_warn = namesv && ckWARN_d(WARN_DEPRECATED)
+                && PerlLIO_stat(name, &st) == 0 && !S_ISDIR(st.st_mode) && !S_ISBLK(st.st_mode)
+                && (io = PerlIO_openn(aTHX_ ":", PERL_SCRIPT_MODE, -1, 0, 0, NULL, 1, &sv)) != NULL;
+            if (io)
+                PerlIO_close(io);
+
+            RESTORE_ERRNO;
+            if (do_warn) {
+                Perl_warner(aTHX_ packWARN(WARN_DEPRECATED), "do \"%s\" failed, '.' is no longer in @INC", name);
+            }
+#endif
+            CLEAR_ERRSV();
+            RETPUSHUNDEF;
+        }
     }
     else
 	SETERRNO(0, SS_NORMAL);
diff --git a/t/lib/warnings/pp_ctl b/t/lib/warnings/pp_ctl
index 9b3f2982e4..27efbcbda5 100644
--- a/t/lib/warnings/pp_ctl
+++ b/t/lib/warnings/pp_ctl
@@ -251,3 +251,16 @@ EXPECT
 use warnings;
 eval 'use 5.006; use 5.10.0';
 EXPECT
+########
+# SKIP ? !$Config{default_inc_includes_dot}
+# NAME check warning for do with no . in @INC
+open my $fh, ">", "dounknown";
+close $fh;
+do "dounknown";
+do "./dounknown";
+no warnings 'deprecated';
+do "dounknown";
+do "./dounknown";
+unlink "dounknown";
+EXPECT
+do "dounknown" failed, '.' is no longer in @INC at - line 3.