Re: command_not_found_handle not run when PATH is empty

[Grisha Levit]

On Wed, Mar 8, 2023 at 4:28 PM Moshe Looks <moshe.looks@gmail.com> wrote:
> This is very old code and I have no idea what the original intention
> was in returning 'name' here or if doing so is still performing useful
> work, but the tests pass at least.

A null $PATH component is treated as the current directory, and bash
treats an empty $PATH as having only a single null component, so we
can't just fail to return a command when $PATH is empty.

The current code's behavior of returning the path as provided when
$PATH is empty accomplishes the goal of "finding" the path in $PATH
but ignores any flags that would normally limit the results to files
that exist/are executable/etc.

This leads to weirdness not just with command_not_found_handle but
with command name completion and `type -a' and `command output as
well.

$ cd /bin
$ PATH= compgen -c -X '!bash'
$ PATH= type -a bash
-bash: type: bash: not found

I think it might make sense to change code that looks at the value of
PATH to explicitly treat an empty value as `.' so that all such
behavior is consistent.

diff --git a/bashline.c b/bashline.c
index 3238b13a..e0d6107c 100644
--- a/bashline.c
+++ b/bashline.c
@@ -2063,6 +2063,8 @@ command_word_completion_function (const char
*hint_text, int state)
  dequoted_hint = bash_dequote_filename (hint, 0);

       path = get_string_value ("PATH");
+      if (path == 0 || *path == '\0')
+ path = ".";
       path_index = dot_in_path = 0;

       /* Initialize the variables for each type of command word. */
diff --git a/findcmd.c b/findcmd.c
index 186871ac..b413c870 100644
--- a/findcmd.c
+++ b/findcmd.c
@@ -256,13 +256,13 @@ _find_user_command_internal (const char *name, int flags)

   /* Search for the value of PATH in both the temporary environments and
      in the regular list of variables. */
-  if (var = find_variable_tempenv ("PATH")) /* XXX could be array? */
-    path_list = value_cell (var);
+  if (var = find_variable_tempenv ("PATH"))
+    path_list = get_variable_value (var);
   else
-    path_list = (char *)NULL;
+    path_list = 0;

   if (path_list == 0 || *path_list == '\0')
-    return (savestring (name));
+    path_list = ".";

   cmd = find_user_command_in_path (name, path_list, flags, (int *)0);

@@ -363,11 +363,14 @@ search_for_command (const char *pathname, int flags)
     {
       if (flags & CMDSRCH_STDPATH)
  path_list = conf_standard_path ();
-      else if (temp_path || path)
- path_list = value_cell (path);
+      else if (path)
+ path_list = get_variable_value (path);
       else
  path_list = 0;

+      if (path_list == 0 || *path_list == '\0')
+ path_list = ".";
+
       command = find_user_command_in_path (pathname, path_list,
FS_EXEC_PREFERRED|FS_NODIRS, &st);

       if (command && hashing_enabled && temp_path == 0 && (flags &
CMDSRCH_HASH))
@@ -440,7 +443,9 @@ user_command_matches (const char *name, int flags,
int state)
    if (stat (".", &dotinfo) < 0)
      dotinfo.st_dev = dotinfo.st_ino = 0; /* so same_file won't match */
    path_list = get_string_value ("PATH");
-        path_index = 0;
+   if (path_list == 0 || *path_list == '\0')
+     path_list = ".";
+   path_index = 0;
  }

       while (path_list && path_list[path_index])