lib: add ![...] syntax for easy "no" forms

This allows defining a CLI command like this:
  `[no] some setting ![VALUE]`
with VALUE being optional for the "no" form, but required for the
positive form.  It's just a `[...]` where the empty branch can only be
taken for commands starting with `no`.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

doc/developer/cli.rst

@@ -139,6 +139,7 @@ by the parser.
    selector: "<" `selector_seq_seq` ">" `varname_token`
            : "{" `selector_seq_seq` "}" `varname_token`
            : "[" `selector_seq_seq` "]" `varname_token`
+           : "![" `selector_seq_seq` "]" `varname_token`
    selector_seq_seq: `selector_seq_seq` "|" `selector_token_seq`
                    : `selector_token_seq`
    selector_token_seq: `selector_token_seq` `selector_token`
@@ -218,6 +219,10 @@ one-or-more selection and repetition.
    provide mutual exclusion. User input matches at most one option.
 -  ``[square brackets]`` -- Contains sequences of tokens that can be omitted.
    ``[<a|b>]`` can be shortened to ``[a|b]``.
+-  ``![exclamation square brackets]`` -- same as ``[square brackets]``, but
+   only allow skipping the contents if the command input starts with ``no``.
+   (For cases where the positive command needs a parameter, but the parameter
+   is optional for the negative case.)
 -  ``{curly|braces}`` -- similar to angle brackets, but instead of mutual
    exclusion, curly braces indicate that one or more of the pipe-separated
    sequences may be provided in any order.

lib/command.c

@@ -74,6 +74,7 @@ const struct message tokennames[] = {
 	item(JOIN_TKN),
 	item(START_TKN),
 	item(END_TKN),
+	item(NEG_ONLY_TKN),
 	{0},
 };
 /* clang-format on */

lib/command_graph.c

@@ -388,6 +388,7 @@ static void cmd_node_names(struct graph_node *gn, struct graph_node *join,
 
 	case START_TKN:
 	case JOIN_TKN:
+	case NEG_ONLY_TKN:
 		/* "<foo|bar> WORD" -> word is not "bar" or "foo" */
 		prevname = NULL;
 		break;
@@ -511,6 +512,9 @@ void cmd_graph_node_print_cb(struct graph_node *gn, struct buffer *buf)
 	case JOIN_TKN:
 		color = "#ddaaff";
 		break;
+	case NEG_ONLY_TKN:
+		color = "#ffddaa";
+		break;
 	case WORD_TKN:
 		color = "#ffffff";
 		break;

lib/command_graph.h

@@ -64,6 +64,7 @@ enum cmd_token_type {
 	JOIN_TKN,  // marks subgraph end
 	START_TKN, // first token in line
 	END_TKN,   // last token in line
+	NEG_ONLY_TKN,    // filter token, match if "no ..." command
 
 	SPECIAL_TKN = FORK_TKN,
 };

lib/command_lex.l

@@ -82,6 +82,7 @@ RANGE           \({NUMBER}[ ]?\-[ ]?{NUMBER}\)
 {VARIABLE}      {yylval->string = XSTRDUP(MTYPE_LEX, yytext); return VARIABLE;}
 {WORD}          {yylval->string = XSTRDUP(MTYPE_LEX, yytext); return WORD;}
 {RANGE}         {yylval->string = XSTRDUP(MTYPE_LEX, yytext); return RANGE;}
+!\[             {yylval->string = NULL; return EXCL_BRACKET;}
 .               {return yytext[0];}
 %%
 

lib/command_match.c

@@ -42,7 +42,7 @@ DEFINE_MTYPE_STATIC(LIB, CMD_MATCHSTACK, "Command Match Stack");
 
 /* matcher helper prototypes */
 static int add_nexthops(struct list *, struct graph_node *,
-			struct graph_node **, size_t);
+			struct graph_node **, size_t, bool);
 
 static enum matcher_rv command_match_r(struct graph_node *, vector,
 				       unsigned int, struct graph_node **,
@@ -79,6 +79,13 @@ static enum match_type match_variable(struct cmd_token *, const char *);
 
 static enum match_type match_mac(const char *, bool);
 
+static bool is_neg(vector vline, size_t idx)
+{
+	if (idx >= vector_active(vline))
+		return false;
+	return !strcmp(vector_slot(vline, idx), "no");
+}
+
 enum matcher_rv command_match(struct graph *cmdgraph, vector vline,
 			      struct list **argv, const struct cmd_element **el)
 {
@@ -248,7 +255,7 @@ static enum matcher_rv command_match_r(struct graph_node *start, vector vline,
 
 	// get all possible nexthops
 	struct list *next = list_new();
-	add_nexthops(next, start, NULL, 0);
+	add_nexthops(next, start, NULL, 0, is_neg(vline, 1));
 
 	// determine the best match
 	for (ALL_LIST_ELEMENTS_RO(next, ln, gn)) {
@@ -349,6 +356,7 @@ enum matcher_rv command_complete(struct graph *graph, vector vline,
 {
 	// pointer to next input token to match
 	char *input_token;
+	bool neg = is_neg(vline, 0);
 
 	struct list *
 		current =
@@ -363,7 +371,7 @@ enum matcher_rv command_complete(struct graph *graph, vector vline,
 
 	// add all children of start node to list
 	struct graph_node *start = vector_slot(graph->nodes, 0);
-	add_nexthops(next, start, &start, 0);
+	add_nexthops(next, start, &start, 0, neg);
 
 	unsigned int idx;
 	for (idx = 0; idx < vector_active(vline) && next->count > 0; idx++) {
@@ -428,7 +436,7 @@ enum matcher_rv command_complete(struct graph *graph, vector vline,
 					listnode_add(next, newstack);
 				} else if (matchtype >= minmatch)
 					add_nexthops(next, gstack[0], gstack,
-						     idx + 1);
+						     idx + 1, neg);
 				break;
 			default:
 				trace_matcher("no_match\n");
@@ -478,7 +486,7 @@ enum matcher_rv command_complete(struct graph *graph, vector vline,
  * output, instead of direct node pointers!
  */
 static int add_nexthops(struct list *list, struct graph_node *node,
-			struct graph_node **stack, size_t stackpos)
+			struct graph_node **stack, size_t stackpos, bool neg)
 {
 	int added = 0;
 	struct graph_node *child;
@@ -494,8 +502,13 @@ static int add_nexthops(struct list *list, struct graph_node *node,
 			if (j != stackpos)
 				continue;
 		}
+
+		if (token->type == NEG_ONLY_TKN && !neg)
+			continue;
+
 		if (token->type >= SPECIAL_TKN && token->type != END_TKN) {
-			added += add_nexthops(list, child, stack, stackpos);
+			added +=
+				add_nexthops(list, child, stack, stackpos, neg);
 		} else {
 			if (stack) {
 				nextstack = XMALLOC(

lib/command_parse.y

@@ -105,6 +105,9 @@
 %token <string> MAC
 %token <string> MAC_PREFIX
 
+/* special syntax, value is irrelevant */
+%token <string> EXCL_BRACKET
+
 /* union types for parsed rules */
 %type <node> start
 %type <node> literal_token
@@ -372,6 +375,19 @@ selector: '[' selector_seq_seq ']' varname_token
 }
 ;
 
+/* ![option] productions */
+selector: EXCL_BRACKET selector_seq_seq ']' varname_token
+{
+  struct graph_node *neg_only = new_token_node (ctx, NEG_ONLY_TKN, NULL, NULL);
+
+  $$ = $2;
+  graph_add_edge ($$.start, neg_only);
+  graph_add_edge (neg_only, $$.end);
+  cmd_token_varname_set ($2.end->data, $4);
+  XFREE (MTYPE_LEX, $4);
+}
+;
+
 %%
 
 #undef scanner

lib/command_py.c

@@ -210,8 +210,8 @@ static PyObject *graph_to_pyobj(struct wrap_graph *wgraph,
 
 				/* plumbing types */
 				item(FORK_TKN) item(JOIN_TKN) item(START_TKN)
-					item(END_TKN) default
+					item(END_TKN) item(NEG_ONLY_TKN) default
-				: wrap->type = "???";
+			    : wrap->type = "???";
 		}
 
 		wrap->deprecated = (tok->attr == CMD_ATTR_DEPRECATED);

tests/lib/cli/test_cli.c

@@ -40,6 +40,8 @@ DUMMY_DEFUN(cmd12, "alt a A.B.C.D");
 DUMMY_DEFUN(cmd13, "alt a X:X::X:X");
 DUMMY_DEFUN(cmd14,
 	    "pat g {  foo A.B.C.D$foo|foo|bar   X:X::X:X$bar| baz } [final]");
+DUMMY_DEFUN(cmd15, "no pat g ![ WORD ]");
+DUMMY_DEFUN(cmd16, "[no] pat h {foo ![A.B.C.D$foo]|bar X:X::X:X$bar} final");
 
 #include "tests/lib/cli/test_cli_clippy.c"
 
@@ -81,5 +83,7 @@ void test_init(int argc, char **argv)
 		install_element(ENABLE_NODE, &cmd13_cmd);
 	}
 	install_element(ENABLE_NODE, &cmd14_cmd);
+	install_element(ENABLE_NODE, &cmd15_cmd);
+	install_element(ENABLE_NODE, &cmd16_cmd);
 	install_element(ENABLE_NODE, &magic_test_cmd);
 }

tests/lib/cli/test_cli.in

@@ -74,6 +74,23 @@ pat f
 pat f foo
 pat f key
 
+no pat g
+no pat g test
+no pat g test more
+
+pat h foo ?1.2.3.4 final
+no pat h foo ?1.2.3.4 final
+pat h foo final
+no pat h foo final
+pat h bar final
+no pat h bar final
+pat h bar 1::2 final
+no pat h bar 1::2 final
+pat h bar 1::2 foo final
+no pat h bar 1::2 foo final
+pat h bar 1::2 foo 1.2.3.4 final
+no pat h bar 1::2 foo 1.2.3.4 final
+
 alt a 	a?b
 alt a 1	.2?.3.4
 alt a 1	:2?	::?3

tests/lib/cli/test_cli.refout.in

@@ -147,7 +147,7 @@ test# papat
 % Command incomplete.
 test# pat 
 a          b          c          d          e          f          
-g          
+g          h          
 test# pat 
 % Command incomplete.
 test# 
@@ -263,6 +263,100 @@ cmd10 with 3 args.
 [01] f@(null): f
 [02] key@(null): key
 test# 
+test# no pat g
+cmd15 with 3 args.
+[00] no@(null): no
+[01] pat@(null): pat
+[02] g@(null): g
+test# no pat g test
+cmd15 with 4 args.
+[00] no@(null): no
+[01] pat@(null): pat
+[02] g@(null): g
+[03] WORD@g: test
+test# no pat g test more
+% [NONE] Unknown command: no pat g test more
+test# 
+test# pat h foo 
+  A.B.C.D  04
+test# pat h foo 1.2.3.4 final
+cmd16 with 5 args.
+[00] pat@(null): pat
+[01] h@(null): h
+[02] foo@(null): foo
+[03] A.B.C.D@foo: 1.2.3.4
+[04] final@(null): final
+test# no pat h foo 
+  A.B.C.D  04
+  bar      05
+  final    07
+test# no pat h foo 1.2.3.4 final
+cmd16 with 6 args.
+[00] no@no: no
+[01] pat@(null): pat
+[02] h@(null): h
+[03] foo@(null): foo
+[04] A.B.C.D@foo: 1.2.3.4
+[05] final@(null): final
+test# pat h foo final
+% [NONE] Unknown command: pat h foo final
+test# no pat h foo final
+cmd16 with 5 args.
+[00] no@no: no
+[01] pat@(null): pat
+[02] h@(null): h
+[03] foo@(null): foo
+[04] final@(null): final
+test# pat h bar final
+% [NONE] Unknown command: pat h bar final
+test# no pat h bar final
+% [NONE] Unknown command: no pat h bar final
+test# pat h bar 1::2 final
+cmd16 with 5 args.
+[00] pat@(null): pat
+[01] h@(null): h
+[02] bar@(null): bar
+[03] X:X::X:X@bar: 1::2
+[04] final@(null): final
+test# no pat h bar 1::2 final
+cmd16 with 6 args.
+[00] no@no: no
+[01] pat@(null): pat
+[02] h@(null): h
+[03] bar@(null): bar
+[04] X:X::X:X@bar: 1::2
+[05] final@(null): final
+test# pat h bar 1::2 foo final
+% [NONE] Unknown command: pat h bar 1::2 foo final
+test# no pat h bar 1::2 foo final
+cmd16 with 7 args.
+[00] no@no: no
+[01] pat@(null): pat
+[02] h@(null): h
+[03] bar@(null): bar
+[04] X:X::X:X@bar: 1::2
+[05] foo@(null): foo
+[06] final@(null): final
+test# pat h bar 1::2 foo 1.2.3.4 final
+cmd16 with 7 args.
+[00] pat@(null): pat
+[01] h@(null): h
+[02] bar@(null): bar
+[03] X:X::X:X@bar: 1::2
+[04] foo@(null): foo
+[05] A.B.C.D@foo: 1.2.3.4
+[06] final@(null): final
+test# no pat h bar 1::2 foo 1.2.3.4 final
+cmd16 with 8 args.
+[00] no@no: no
+[01] pat@(null): pat
+[02] h@(null): h
+[03] bar@(null): bar
+[04] X:X::X:X@bar: 1::2
+[05] foo@(null): foo
+[06] A.B.C.D@foo: 1.2.3.4
+[07] final@(null): final
+test# 
 test# alt a 
 test# alt a a
   WORD      02

tools/permutations.c

@@ -61,9 +61,22 @@ void permute(struct graph_node *start)
 	struct cmd_token *stok = start->data;
 	struct graph_node *gnn;
 	struct listnode *ln;
+	bool is_neg = false;
 
 	// recursive dfs
 	listnode_add(position, start);
+
+	for (ALL_LIST_ELEMENTS_RO(position, ln, gnn)) {
+		struct cmd_token *tok = gnn->data;
+
+		if (tok->type == WORD_TKN && !strcmp(tok->text, "no")) {
+			is_neg = true;
+			break;
+		}
+		if (tok->type < SPECIAL_TKN)
+			break;
+	}
+
 	for (unsigned int i = 0; i < vector_active(start->to); i++) {
 		struct graph_node *gn = vector_slot(start->to, i);
 		struct cmd_token *tok = gn->data;
@@ -82,6 +95,9 @@ void permute(struct graph_node *start)
 			fprintf(stdout, "\n");
 		} else {
 			bool skip = false;
+
+			if (tok->type == NEG_ONLY_TKN && !is_neg)
+				continue;
 			if (stok->type == FORK_TKN && tok->type != FORK_TKN)
 				for (ALL_LIST_ELEMENTS_RO(position, ln, gnn))
 					if (gnn == gn) {