lineedit: support empty PATH entries in tab completion

Zero-length path prefixes can be specified in PATH as a leading or
trailing colon or two adjacent colons.  POSIX says that the use of
zero-length prefixes to refer to the current directory is a legacy
feature.  Nonetheless the shells in BusyBox respect this feature,
as does 'which'.

Tab-completion of executables using PATH should support this too.

function                                             old     new   delta
complete_cmd_dir_file                                934     931      -3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-3)               Total: -3 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 4 insertions, 6 deletions

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 367396b91..b0adcf140 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -769,8 +769,6 @@ static unsigned path_parse(char ***p)
                 if (!tmp)
                         break;
                 tmp++;
-                if (*tmp == '\0')
-                        break;  /* :<empty> */
                 npth++;
         }
 
@@ -782,8 +780,6 @@ static unsigned path_parse(char ***p)
                 if (!tmp)
                         break;
                 *tmp++ = '\0'; /* ':' -> '\0' */
-                if (*tmp == '\0')
-                        break; /* :<empty> */
                 res[npth++] = tmp;
         }
         /* special case: "match subdirectories of the current directory" */
@@ -854,6 +850,7 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
                 struct dirent *next;
                 struct stat st;
                 char *found;
+                const char *lpath;
 
                 if (paths[i] == NULL) { /* path_parse()'s last component? */
                         /* in PATH completion, current dir's subdir names
@@ -863,7 +860,8 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
                         paths[i] = (char *)".";
                 }
 
-                dir = opendir(paths[i]);
+                lpath = *paths[i] ? paths[i] : ".";
+                dir = opendir(lpath);
                 if (!dir)
                         continue; /* don't print an error */
 
@@ -878,7 +876,7 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
                         if (strncmp(basecmd, name_found, baselen) != 0)
                                 continue; /* no */
 
-                        found = concat_path_file(paths[i], name_found);
+                        found = concat_path_file(lpath, name_found);
                         /* NB: stat() first so that we see is it a directory;
                          * but if that fails, use lstat() so that
                          * we still match dangling links */