keyval: Fix and clarify grammar
The grammar has a few issues:
* key-fragment = / [^=,.]* /
Prose restricts key fragments: they "must be valid QAPI names or
consist only of decimal digits". Technically, '' consists only of
decimal digits. The code rejects that. Fix the grammar.
* val = { / [^,]* / | ',,' }
Use + instead of *. Accepts the same language.
* val-no-key = / [^=,]* /
The code rejects an empty value. Fix the grammar.
* Section "Additional syntax for use with an implied key" is
confusing. Rewrite it.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201011073505.1185335-2-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/util/keyval.c b/util/keyval.c
index 13def4a..82d8497 100644
--- a/util/keyval.c
+++ b/util/keyval.c
@@ -16,8 +16,8 @@
* key-vals = [ key-val { ',' key-val } [ ',' ] ]
* key-val = key '=' val
* key = key-fragment { '.' key-fragment }
- * key-fragment = / [^=,.]* /
- * val = { / [^,]* / | ',,' }
+ * key-fragment = / [^=,.]+ /
+ * val = { / [^,]+ / | ',,' }
*
* Semantics defined by reduction to JSON:
*
@@ -71,12 +71,16 @@
* Awkward. Note that we carefully restrict alternate types to avoid
* similar ambiguity.
*
- * Additional syntax for use with an implied key:
+ * Alternative syntax for use with an implied key:
*
- * key-vals-ik = val-no-key [ ',' key-vals ]
- * val-no-key = / [^=,]* /
+ * key-vals = [ key-val-1st { ',' key-val } [ ',' ] ]
+ * key-val-1st = val-no-key | key-val
+ * val-no-key = / [^=,]+ /
*
- * where no-key is syntactic sugar for implied-key=val-no-key.
+ * where val-no-key is syntactic sugar for implied-key=val-no-key.
+ *
+ * Note that you can't use the sugared form when the value contains
+ * '=' or ','.
*/
#include "qemu/osdep.h"
