Setting quickfix/location list context

[Yegappan Lakshmanan]

Hi all,

The attached patch adds support for setting and getting a context to/from
a quickfix/location list. There is a refcount problem with this diff (which I am
not able to solve).

If the context is a number or a string, then the patch works without any
issues. If the context is a List or a Dict, then Vim crashes if garbage
collection runs. For example, the following works:

    :call setqflist([], 'a', {'context':[1,2,3]})
    :echo getqflist({'context':1})

But the following doesn't work:

    :call setqflist([], 'a', {'context':[1,2,3]})
    :call garbagecollect()
    :echo getqflist({'context':1})

Any suggestions on how to copy the context with proper update to the
reference count so that garbage collection doesn't free the List/Dict?

Thanks,
Yegappan

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diff --git a/src/quickfix.c b/src/quickfix.c
index 2fa6ed9..8143738 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -57,6 +57,7 @@ typedef struct qf_list_S
     int                qf_nonevalid;   /* TRUE if not a single valid entry 
found */
     char_u     *qf_title;      /* title derived from the command that created
                                 * the error list */
+    typval_T   *qf_ctx;        /* context set by setqflist/setloclist */
 } qf_list_T;
 
 struct qf_info_S
@@ -1545,6 +1546,14 @@ copy_loclist(win_T *from, win_T *to)
            to_qfl->qf_title = vim_strsave(from_qfl->qf_title);
        else
            to_qfl->qf_title = NULL;
+       if (from_qfl->qf_ctx != NULL)
+       {
+           to_qfl->qf_ctx = alloc_tv();
+           if (to_qfl->qf_ctx != NULL)
+               copy_tv(from_qfl->qf_ctx, to_qfl->qf_ctx);
+       }
+       else
+           to_qfl->qf_ctx = NULL;
 
        if (from_qfl->qf_count)
        {
@@ -2698,6 +2707,8 @@ qf_free(qf_info_T *qi, int idx)
     }
     vim_free(qi->qf_lists[idx].qf_title);
     qi->qf_lists[idx].qf_title = NULL;
+    free_tv(qi->qf_lists[idx].qf_ctx);
+    qi->qf_lists[idx].qf_ctx = NULL;
     qi->qf_lists[idx].qf_index = 0;
 
     qf_clean_dir_stack(&qi->qf_dir_stack);
@@ -4613,6 +4624,7 @@ enum {
     QF_GETLIST_ITEMS   = 0x2,
     QF_GETLIST_NR      = 0x4,
     QF_GETLIST_WINID   = 0x8,
+    QF_GETLIST_CONTEXT = 0x10,
     QF_GETLIST_ALL     = 0xFF
 };
 
@@ -4661,6 +4673,9 @@ get_errorlist_properties(win_T *wp, dict_T *what, dict_T 
*retdict)
     if (dict_find(what, (char_u *)"winid", -1) != NULL)
        flags |= QF_GETLIST_WINID;
 
+    if (dict_find(what, (char_u *)"context", -1) != NULL)
+       flags |= QF_GETLIST_CONTEXT;
+
     if (flags & QF_GETLIST_TITLE)
     {
        char_u  *t;
@@ -4679,6 +4694,22 @@ get_errorlist_properties(win_T *wp, dict_T *what, dict_T 
*retdict)
            status = dict_add_nr_str(retdict, "winid", win->w_id, NULL);
     }
 
+    if ((status == OK) && (flags & QF_GETLIST_CONTEXT))
+    {
+       if (qi->qf_lists[qf_idx].qf_ctx != NULL)
+       {
+           dictitem_T  *di;
+           di = dictitem_alloc((char_u *)"context");
+           if (di != NULL)
+           {
+               copy_tv(qi->qf_lists[qf_idx].qf_ctx, &di->di_tv);
+               dict_add(retdict, di);
+           }
+       }
+       else
+           status = dict_add_nr_str(retdict, "context", 0L, (char_u *)"");
+    }
+
     return status;
 }
 
@@ -4838,6 +4869,16 @@ qf_set_properties(qf_info_T *qi, dict_T *what)
        }
     }
 
+    if ((di = dict_find(what, (char_u *)"context", -1)) != NULL)
+    {
+       typval_T        *ctx;
+       free_tv(qi->qf_lists[qi->qf_curlist].qf_ctx);
+       ctx =  alloc_tv();
+       if (ctx != NULL)
+           copy_tv(&di->di_tv, ctx);
+       qi->qf_lists[qi->qf_curlist].qf_ctx = ctx;
+    }
+
     return retval;
 }