vsh: Rework logic for picking which argument is to be completed

Currently the code decides which option to complete by looking into the
input string and trying to infer it based on whether we are at the
end position as we truncate the string to complete to the current cursor
position.

That basically means that only the last-parsed option will be up for
completion.

Replace the logic by remembering which is the last option rather than
using two different position checks and base the completion decision on
that and the actual value of the last argument (see comment).

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

tools/vsh.c

@@ -1390,6 +1390,7 @@ vshCommandParse(vshControl *ctl, vshCommandParser *parser, vshCmd **partial)
     char *tkdata = NULL;
     vshCmd *clast = NULL;
     vshCmdOpt *first = NULL;
+    vshCmdOpt *last = NULL;
     const vshCmdDef *cmd = NULL;
 
     if (!partial) {
@@ -1397,7 +1398,6 @@ vshCommandParse(vshControl *ctl, vshCommandParser *parser, vshCmd **partial)
     }
 
     while (1) {
-        vshCmdOpt *last = NULL;
         vshCommandToken tk;
         bool data_only = false;
         uint64_t opts_need_arg = 0;
@@ -1406,6 +1406,7 @@ vshCommandParse(vshControl *ctl, vshCommandParser *parser, vshCmd **partial)
 
         cmd = NULL;
         first = NULL;
+        last = NULL;
 
         if (partial) {
             g_clear_pointer(partial, vshCommandFree);
@@ -1589,6 +1590,7 @@ vshCommandParse(vshControl *ctl, vshCommandParser *parser, vshCmd **partial)
             }
 
             c->opts = g_steal_pointer(&first);
+            c->lastopt = last;
             c->def = cmd;
             c->next = NULL;
 
@@ -1622,6 +1624,7 @@ vshCommandParse(vshControl *ctl, vshCommandParser *parser, vshCmd **partial)
 
         tmp = g_new0(vshCmd, 1);
         tmp->opts = first;
+        tmp->lastopt = last;
         tmp->def = cmd;
 
         *partial = tmp;
@@ -2735,27 +2738,6 @@ vshReadlineOptionsGenerator(const vshCmdDef *cmd,
 }
 
 
-static const vshCmdOptDef *
-vshReadlineCommandFindOpt(const vshCmd *partial)
-{
-    const vshCmd *tmp = partial;
-
-    while (tmp) {
-        const vshCmdOpt *opt = tmp->opts;
-
-        while (opt) {
-            if (opt->completeThis)
-                return opt->def;
-
-            opt = opt->next;
-        }
-        tmp = tmp->next;
-    }
-
-    return NULL;
-}
-
-
 static int
 vshCompleterFilter(char ***list,
                    const char *text)
@@ -2802,7 +2784,6 @@ vshReadlineParse(const char *text, int state)
     if (!state) {
         g_autoptr(vshCmd) partial = NULL;
         const vshCmdDef *cmd = NULL;
-        const vshCmdOptDef *opt = NULL;
         g_autofree char *line = g_strdup(rl_line_buffer);
 
         g_clear_pointer(&list, g_strfreev);
@@ -2828,16 +2809,36 @@ vshReadlineParse(const char *text, int state)
             cmd = NULL;
         }
 
-        opt = vshReadlineCommandFindOpt(partial);
-
         if (!cmd) {
             list = vshReadlineCommandGenerator();
-        } else if (!opt || opt->type == VSH_OT_BOOL) {
-            list = vshReadlineOptionsGenerator(cmd, partial);
-        } else if (opt && opt->completer) {
-            list = opt->completer(autoCompleteOpaque,
+        } else {
+            bool complete_argument = false;
+
+            /* attempt completion only when:
+                - there is an argument
+                - it has the 'data' field filled
+                - it has a completer (rules out booleans)
+            */
+            if (partial->lastopt && partial->lastopt->data && partial->lastopt->def->completer) {
+                /* Furthermore we want to do the completion only at the point of
+                 * user's cursor. This is the case if:
+                 * - value in 'data' is equal to 'text' (last component of the completed command)
+                 * - value in 'data' is a space when 'text' is empty (quirk)
+                 */
+                if (STREQ_NULLABLE(partial->lastopt->data, text))
+                    complete_argument = true;
+
+                if (STREQ_NULLABLE(partial->lastopt->data, " ") && *text == '\0')
+                    complete_argument = true;
+            }
+
+            if (complete_argument) {
+                list = partial->lastopt->def->completer(autoCompleteOpaque,
                                                         partial,
-                                  opt->completer_flags);
+                                                        partial->lastopt->def->completer_flags);
+            } else {
+                list = vshReadlineOptionsGenerator(cmd, partial);
+            }
         }
 
         /* Escape completions, if needed (i.e. argument

tools/vsh.h

@@ -178,6 +178,7 @@ struct _vshCmdDef {
 struct _vshCmd {
     const vshCmdDef *def;       /* command definition */
     vshCmdOpt *opts;            /* list of command arguments */
+    vshCmdOpt *lastopt;         /* last option of the commandline */
     vshCmd *next;               /* next command */
     bool skipChecks;            /* skip validity checks when retrieving opts */
 };