plugins: set non_numeric_ids flag based on getmanifest `nonnumericids…

…` field.

And document support for it.

Signed-off-by: Rusty Russell <[email protected]>
Changelog-Added: Plugins: `getmanfest` response can contain `nonnumericids` to indicate support for modern string-based JSON request ids.
Changelog-Deprecated: Plugins: numeric JSON request ids: modern ones will be strings (see doc/lightningd-rpc.7.md!)

doc/PLUGINS.md

@@ -136,6 +136,7 @@ example:
 	  "method": "mycustomnotification"
 	}
   ],
+  "nonnumericids": true,
   "dynamic": true
 }
 ```
@@ -158,6 +159,13 @@ you plan on removing them: this will disable them if the user sets
 `allow-deprecated-apis` to false (which every developer should do,
 right?).
 
+The `nonnumericids` indicates that the plugin can handle
+string JSON request `id` fields: prior to v22.11 lightningd used numbers 
+for these, and the change to strings broke some plugins.  If not set,
+then strings will be used once this feature is removed after v23.05.
+See [the lightning-rpc documentation][lightning-rpc.7.md] for how to handle
+JSON `id` fields!
+
 The `dynamic` indicates if the plugin can be managed after `lightningd`
 has been started using the [plugin][lightning-plugin] JSON-RPC command. Critical plugins that should not be stopped should set it
 to false. Plugin `options` can be passed to dynamic plugins as argument to the `plugin` command .
@@ -1781,3 +1789,4 @@ The plugin must broadcast it and respond with the following fields:
 [bolt9]: https://github.com/lightning/bolts/blob/master/09-features.md
 [lightning-plugin]: lightning-plugin.7.md
 [pyln-client]: ../contrib/pyln-client
+[lightning-rpc.7.md]: lightning-rpc.7.md

lightningd/plugin.c

@@ -291,6 +291,7 @@ struct plugin *plugin_register(struct plugins *plugins, const char* path TAKES,
 	p->notification_topics = tal_arr(p, const char *, 0);
 	p->subscriptions = NULL;
 	p->dynamic = false;
+	p->non_numeric_ids = false;
 	p->index = plugins->plugin_idx++;
 
 	p->log = new_log(p, plugins->log_book, NULL, "plugin-%s", p->shortname);
@@ -1528,6 +1529,20 @@ static const char *plugin_parse_getmanifest_response(const char *buffer,
 		}
 	}
 
+	tok = json_get_member(buffer, resulttok, "nonnumericids");
+	if (tok) {
+		if (!json_to_bool(&plugin->non_numeric_ids, buffer, tok))
+			return tal_fmt(plugin,
+				       "Invalid nonnumericids: %.*s",
+				       json_tok_full_len(tok),
+				       json_tok_full(buffer, tok));
+		if (!deprecated_apis && !plugin->non_numeric_ids)
+			return tal_fmt(plugin,
+				       "Plugin does not allow nonnumericids");
+	} else
+		/* Default is false in deprecated mode */
+		plugin->non_numeric_ids = !deprecated_apis;
+
 	err = plugin_notifications_add(buffer, resulttok, plugin);
 	if (!err)
 		err = plugin_opts_add(plugin, buffer, resulttok);

lightningd/plugin.h

@@ -81,6 +81,9 @@ struct plugin {
 	 * C-lightning should terminate as well.  */
 	bool important;
 
+	/* Can this handle non-numeric JSON ids? */
+	bool non_numeric_ids;
+
 	/* Parameters for dynamically-started plugins. */
 	const char *parambuf;
 	const jsmntok_t *params;