opt: add opt_unregister.

Sometimes we all make mistakes.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

ccan/opt/opt.c

@@ -176,6 +176,23 @@ void _opt_register(const char *names, enum opt_type type,
 	add_opt(&opt);
 }
 
+bool opt_unregister(const char *names)
+{
+	int found = -1, i;
+
+	for (i = 0; i < opt_count; i++) {
+		if (opt_table[i].type == OPT_SUBTABLE)
+			continue;
+		if (strcmp(opt_table[i].names, names) == 0)
+			found = i;
+	}
+	if (found == -1)
+		return false;
+	opt_count--;
+	memmove(&opt_table[found], &opt_table[found+1], opt_count - found);
+	return true;
+}
+
 void opt_register_table(const struct opt_table entry[], const char *desc)
 {
 	unsigned int i, start = opt_count;

ccan/opt/opt.h

@@ -228,6 +228,15 @@ void opt_register_table(const struct opt_table *table, const char *desc);
 	_opt_register((names), OPT_CB_ARG((cb), OPT_EARLY, (show),(arg)), \
 		      (arg), (desc))
 
+/**
+ * opt_unregister - unregister an option.
+ * @names: the names it was registered with.
+ *
+ * This undoes opt_register[_early]_[no]arg.  Returns true if the option was
+ * found, otherwise false.
+ */
+bool opt_unregister(const char *names);
+
 /**
  * opt_parse - parse arguments.
  * @argc: pointer to argc

ccan/opt/test/run-unregister.c

+#include <ccan/tap/tap.h>
+#include <stdlib.h>
+#include <ccan/opt/opt.c>
+#include <ccan/opt/usage.c>
+#include <ccan/opt/helpers.c>
+#include <ccan/opt/parse.c>
+#include "utils.h"
+
+int main(int argc, char *argv[])
+{
+	const char *myname = argv[0];
+
+	plan_tests(14);
+
+	/* Simple short arg.*/
+	opt_register_noarg("--aaa|-a", test_noarg, NULL, "AAAAAAll");
+	opt_register_noarg("-b", test_noarg, NULL, "AAAAAAll");
+
+	/* We can't unregister wrong ones, but can unregister correct one */
+	ok1(!opt_unregister("--aaa"));
+	ok1(!opt_unregister("-a"));
+	ok1(opt_unregister("--aaa|-a"));
+
+	/* Arg parsing works as if we'd never registered it */
+	ok1(parse_args(&argc, &argv, "-b", NULL));
+	ok1(argc == 1);
+	ok1(argv[0] == myname);
+	ok1(argv[1] == NULL);
+	ok1(test_cb_called == 1);
+
+	ok1(!parse_args(&argc, &argv, "--aaa", NULL));
+
+	/* We can still add another one OK. */
+	opt_register_noarg("-c", test_noarg, NULL, "AAAAAAll");
+	ok1(parse_args(&argc, &argv, "-c", NULL));
+	ok1(argc == 1);
+	ok1(argv[0] == myname);
+	ok1(argv[1] == NULL);
+	ok1(test_cb_called == 2);
+
+	/* parse_args allocates argv */
+	free(argv);
+	return exit_status();
+}