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common: allow optional fields in json_scan().

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Currently it fails if a field is missing, but sometimes that's OK.  So
allow a fieldname ending in `?` to mean "skip over if it's missing".

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2023-06-01 13:42:21 +09:30
parent 1e457bd48d
commit 2bbd9b8a72
2 changed files with 59 additions and 15 deletions
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56
common/json_parse.c
View file

@ -193,6 +193,9 @@ static const char *handle_percent(const char *buffer,
void **p;
p = va_arg(*ap, void **);
talfmt = va_arg(*ap, void *(*)(void *, const char *, const jsmntok_t *));
/* If we're skipping this, don't call fmt! */
if (!tok)
return NULL;
*p = talfmt(ctx, buffer, tok);
if (*p != NULL)
return NULL;
@ -202,6 +205,9 @@ static const char *handle_percent(const char *buffer,
p = va_arg(*ap, void *);
fmt = va_arg(*ap, bool (*)(const char *, const jsmntok_t *, void *));
/* If we're skipping this, don't call fmt! */
if (!tok)
return NULL;
if (fmt(buffer, tok, p))
return NULL;
}
@ -215,7 +221,8 @@ static const char *handle_percent(const char *buffer,
/* GUIDE := OBJ | ARRAY | '%'
* OBJ := '{' FIELDLIST '}'
* FIELDLIST := FIELD [',' FIELD]*
* FIELD := LITERAL ':' FIELDVAL
* FIELD := MEMBER ':' FIELDVAL
* MEMBER := LITERAL | LITERAL '?'
* FIELDVAL := OBJ | ARRAY | LITERAL | '%'
* ARRAY := '[' ARRLIST ']'
* ARRLIST := ARRELEM [',' ARRELEM]*
@ -264,6 +271,15 @@ static void guide_must_be(const char **guide, char c)
assert(actual == c);
}
static bool guide_maybe_optional(const char **guide)
{
if (**guide == '?') {
guide_consume_one(guide);
return true;
}
return false;
}
/* Recursion: return NULL on success, errmsg on fail */
static const char *parse_obj(const char *buffer,
const jsmntok_t *tok,
@ -325,8 +341,8 @@ static const char *parse_fieldval(const char *buffer,
/* Literal must match exactly (modulo quotes for strings) */
parse_literal(guide, &literal, &len);
if (!memeq(buffer + tok->start, tok->end - tok->start,
literal, len)) {
if (tok && !memeq(buffer + tok->start, tok->end - tok->start,
literal, len)) {
return tal_fmt(tmpctx,
"%.*s does not match expected %.*s",
json_tok_full_len(tok),
@ -345,14 +361,20 @@ static const char *parse_field(const char *buffer,
const jsmntok_t *member;
size_t len;
const char *memname;
bool optional;
parse_literal(guide, &memname, &len);
optional = guide_maybe_optional(guide);
guide_must_be(guide, ':');
member = json_get_membern(buffer, tok, memname, len);
if (!member) {
return tal_fmt(tmpctx, "object does not have member %.*s",
(int)len, memname);
if (tok) {
member = json_get_membern(buffer, tok, memname, len);
if (!member && !optional) {
return tal_fmt(tmpctx, "object does not have member %.*s",
(int)len, memname);
}
} else {
member = NULL;
}
return parse_fieldval(buffer, member, guide, ap);
@ -385,7 +407,7 @@ static const char *parse_obj(const char *buffer,
guide_must_be(guide, '{');
if (tok->type != JSMN_OBJECT) {
if (tok && tok->type != JSMN_OBJECT) {
return tal_fmt(tmpctx, "token is not an object: %.*s",
json_tok_full_len(tok),
json_tok_full(buffer, tok));
@ -410,12 +432,16 @@ static const char *parse_arrelem(const char *buffer,
parse_number(guide, &idx);
guide_must_be(guide, ':');
member = json_get_arr(tok, idx);
if (!member) {
return tal_fmt(tmpctx, "token has no index %u: %.*s",
idx,
json_tok_full_len(tok),
json_tok_full(buffer, tok));
if (tok) {
member = json_get_arr(tok, idx);
if (!member) {
return tal_fmt(tmpctx, "token has no index %u: %.*s",
idx,
json_tok_full_len(tok),
json_tok_full(buffer, tok));
}
} else {
member = NULL;
}
return parse_fieldval(buffer, member, guide, ap);
@ -448,7 +474,7 @@ static const char *parse_arr(const char *buffer,
guide_must_be(guide, '[');
if (tok->type != JSMN_ARRAY) {
if (tok && tok->type != JSMN_ARRAY) {
return tal_fmt(tmpctx, "token is not an array: %.*s",
json_tok_full_len(tok),
json_tok_full(buffer, tok));

18
common/test/run-json_scan.c
View file

@ -146,6 +146,24 @@ int main(int argc, char *argv[])
assert(!json_scan(tmpctx, buf, toks, "{2:two,1:one,3:{three:{deeper:17}},arr:[1:2]}"));
assert(!json_scan(tmpctx, buf, toks, "{2:two,1:one,3:{three:{deeper:17}},arr:[1:2,2:[0:3,1:4]]}"));
/* Optional fields which are present are fine. */
assert(!json_scan(tmpctx, buf, toks, "{1?:one}"));
assert(!json_scan(tmpctx, buf, toks, "{1?:one,2?:two}"));
assert(!json_scan(tmpctx, buf, toks, "{2?:two,1?:one}"));
assert(!json_scan(tmpctx, buf, toks, "{2?:two,1?:one,3?:{three?:{deeper?:17}}}"));
assert(!json_scan(tmpctx, buf, toks, "{2?:two,1?:one,3?:{three?:{deeper?:17}},arr?:[0:{1?:arrone}]}"));
assert(!json_scan(tmpctx, buf, toks, "{2?:two,1?:one,3?:{three?:{deeper?:17}},arr?:[1:2]}"));
assert(!json_scan(tmpctx, buf, toks, "{2?:two,1?:one,3?:{three?:{deeper?:17}},arr?:[1:2,2:[0:3,1:4]]}"));
/* Optional field which are missing are fine too */
assert(!json_scan(tmpctx, buf, toks, "{5?:one}"));
assert(!json_scan(tmpctx, buf, toks, "{1:one,5?:two}"));
assert(!json_scan(tmpctx, buf, toks, "{2:two,5?:one}"));
assert(!json_scan(tmpctx, buf, toks, "{2:two,1:one,5?:{three:{deeper:17}}}"));
assert(!json_scan(tmpctx, buf, toks, "{2:two,1:one,3:{five?:{deeper:17}},arr:[0:{1:arrone}]}"));
assert(!json_scan(tmpctx, buf, toks, "{2:two,1:one,3:{three:{notdeeper?:17}},arr:[1:2]}"));
assert(!json_scan(tmpctx, buf, toks, "{2:two,1:one,3:{three:{deeper:17}},notarr?:[1:2,2:[0:3,1:4]]}"));
/* These do not match */
err = json_scan(tmpctx, buf, toks, "{2:one}");
assert(streq(err, "Parsing '{2:one': \"two\" does not match expected one"));