[Help-bash] programmable completions via compgen -F

[Муравьев Александр]

Hello!

I am unable to use "compgen -F" and made a patch to make it works.

I explored source code and noted that programmable completion uses 
"pcomp_line" buffer, which is assigned to rl_line_buffer when you press 
<TAB> in bash and programmable completion activates (inside 
programmable_completions method in pcomplete.c). However, 
gen_compspec_completion mathod called by compgen realization method just 
assign pcomp_line to NULL. I made temporary buffer, which imitates line 
buffer from readline library (rl_line_buffer) and assign pcomp_line to 
it. That is my patch. Please, tell me how to improve it (if it is ugly).

Hope that it will be possible to use "compgen -F" in new BASH version.

My BASH version is "5.0.11(11)-release", OS "Ubuntu 18.04.3 LTS", 
machine "x86_64".

Here is patch:

> diff --git a/builtins/complete.def b/builtins/complete.def
> index 76b3eedd..e253fc60 100644
> --- a/builtins/complete.def
> +++ b/builtins/complete.def
> @@ -709,6 +709,8 @@ compgen_builtin (list)
>    char *word, **matches;
>    char *old_line;
>    int old_ind;
> +  char pcomp_local[4096];
> +  char *last_word = NULL;
>
>    if (list == 0)
>      return (EXECUTION_SUCCESS);
> @@ -753,9 +755,55 @@ compgen_builtin (list)
>    /* probably don't have to save these, just being safe */
>    old_line = pcomp_line;
>    old_ind = pcomp_ind;
> -  pcomp_line = (char *)NULL;
> -  pcomp_ind = 0;
> -  sl = gen_compspec_completions (cs, "compgen", word, 0, 0, 0);
> +
> +  {
> +      WORD_LIST *cword = list;
> +      if (cword && cword->word
> +          && strlen(cword->word->word) > 0)
> +      {
> +          last_word = cword->word->word;
> +      }
> +      *pcomp_local = '\0';
> +      if (cword && cword->word)
> +      {
> +          strcat(pcomp_local, cword->word->word);
> +          if (strlen(cword->word->word) > 0)
> +          {
> +              last_word = cword->word->word;
> +          }
> +          cword = cword->next;
> +      }
> +      while (cword)
> +      {
> +          if (strlen(cword->word->word) > 0)
> +          {
> +              last_word = cword->word->word;
> +          }
> +          strcat(pcomp_local, " ");
> +          strcat(pcomp_local, cword->word->word);
> +          cword = cword->next;
> +      }
> +  }
> +  pcomp_line = pcomp_local;
> +  pcomp_ind = strlen(pcomp_local);
> +
> +  sl = gen_compspec_completions (cs, "compgen", word, 0, pcomp_ind, 0);
> +  if (sl != 0 && sl->list_len == 1)
> +  {
> +      int last_word_len = strlen(last_word);
> +      int strcmp_complete_res = strncmp(*(sl->list), last_word,
> +                                        last_word_len);
> +      if (0 == strcmp_complete_res
> +            && strlen(*(sl->list)) == last_word_len + 1
> +            && (*(sl->list))[last_word_len] == ' ')
> +      {
> +        /* User already enter this word. Go to next one. */
> +        strcat(pcomp_local, " ");
> +        pcomp_ind++;
> +        sl = gen_compspec_completions (cs, "compgen", word, 0, 
> pcomp_ind, 0);
> +      }
> +  }
> +
>    pcomp_line = old_line;
>    pcomp_ind = old_ind;