assert NOARG/NONEG behavior of parse-options callbacks

When we define a parse-options callback, the flags we put in the option
struct must match what the callback expects. For example, a callback
which does not handle the "unset" parameter should only be used with
PARSE_OPT_NONEG. But since the callback and the option struct are not
defined next to each other, it's easy to get this wrong (as earlier
patches in this series show).

Fortunately, the compiler can help us here: compiling with
-Wunused-parameters can show us which callbacks ignore their "unset"
parameters (and likewise, ones that ignore "arg" expect to be triggered
with PARSE_OPT_NOARG).

But after we've inspected a callback and determined that all of its
callers use the right flags, what do we do next? We'd like to silence
the compiler warning, but do so in a way that will catch any wrong calls
in the future.

We can do that by actually checking those variables and asserting that
they match our expectations. Because this is such a common pattern,
we'll introduce some helper macros. The resulting messages aren't
as descriptive as we could make them, but the file/line information from
BUG() is enough to identify the problem (and anyway, the point is that
these should never be seen).

Each of the annotated callbacks in this patch triggers
-Wunused-parameters, and was manually inspected to make sure all callers
use the correct options (so none of these BUGs should be triggerable).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/apply.c b/apply.c
index c4c9f849b1..3746310cef 100644
--- a/apply.c
+++ b/apply.c
@@ -4772,6 +4772,9 @@ static int apply_option_parse_exclude(const struct option *opt,
 				      const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	add_name_limit(state, arg, 1);
 	return 0;
 }
@@ -4780,6 +4783,9 @@ static int apply_option_parse_include(const struct option *opt,
 				      const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	add_name_limit(state, arg, 0);
 	state->has_include = 1;
 	return 0;
@@ -4790,6 +4796,9 @@ static int apply_option_parse_p(const struct option *opt,
 				int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	state->p_value = atoi(arg);
 	state->p_value_known = 1;
 	return 0;
@@ -4799,6 +4808,9 @@ static int apply_option_parse_space_change(const struct option *opt,
 					   const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_ARG(arg);
+
 	if (unset)
 		state->ws_ignore_action = ignore_ws_none;
 	else
@@ -4810,6 +4822,9 @@ static int apply_option_parse_whitespace(const struct option *opt,
 					 const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	state->whitespace_option = arg;
 	if (parse_whitespace_option(state, arg))
 		return -1;
@@ -4820,6 +4835,9 @@ static int apply_option_parse_directory(const struct option *opt,
 					const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	strbuf_reset(&state->root);
 	strbuf_addstr(&state->root, arg);
 	strbuf_complete(&state->root, '/');