Add PSBT version setting RPC to aid with debugging and compatibility

PSBTv2 support is quite low in the ecosystem, so having a call to convert
log messages and the like should be useful since they'll often be in v2.

Changelog-Added: Added setpsbtversion RPC to aid debugging and compatibility

doc/Makefile

@@ -86,6 +86,7 @@ MANPAGES := doc/lightning-cli.1 \
 	doc/lightning-sendonionmessage.7 \
 	doc/lightning-sendpay.7 \
 	doc/lightning-setchannel.7 \
+	doc/lightning-setpsbtversion.7 \
 	doc/lightning-sendcustommsg.7 \
 	doc/lightning-signinvoice.7 \
 	doc/lightning-signmessage.7 \

doc/index.rst

@@ -119,6 +119,7 @@ Core Lightning Documentation
    lightning-sendpay <lightning-sendpay.7.md>
    lightning-sendpsbt <lightning-sendpsbt.7.md>
    lightning-setchannel <lightning-setchannel.7.md>
+   lightning-setpsbtversion <lightning-setpsbtversion.7.md>
    lightning-signinvoice <lightning-signinvoice.7.md>
    lightning-signmessage <lightning-signmessage.7.md>
    lightning-signpsbt <lightning-signpsbt.7.md>

doc/lightning-setpsbtversion.7.md

@@ -0,0 +1,63 @@
+lightning-setpsbtversion -- Command for setting PSBT version
+============================================================
+
+SYNOPSIS
+--------
+
+**setpsbtversion** *psbt* *version*
+
+DESCRIPTION
+-----------
+
+The **setpsbtversion** RPC command converts the provided PSBT to the given version, and returns the base64 result of the conversion. Returns an error if version is invalid.
+
+- *psbt*: The PSBT to change versions.
+- *version*: The version to set. 
+
+EXAMPLE JSON REQUEST
+------------
+```json
+{
+  "id": 82,
+  "method": "setpsbtversion",
+  "params": {
+    "psbt": "cHNidP8BAAoCAAAAAAAAAAAAAA==",
+    "version": "2"
+  }
+}
+```
+
+RETURN VALUE
+------------
+
+If successful the command returns a converted PSBT of the requested version.
+
+On failure, an error is returned.
+
+The following error codes may occur:
+
+- -32602: Parameter missed or malformed;
+
+EXAMPLE JSON RESPONSE
+-----
+```json
+{
+    "psbt": "cHNidP8BAgQCAAAAAQQBAAEFAQABBgEDAfsEAgAAAAA="
+}
+```
+
+
+AUTHOR
+------
+
+Gregory Sanders <<gsanders87@gmail.com>> is mainly responsible.
+
+SEE ALSO
+--------
+
+lightning-fundpsbt(7), lightning-utxopsbt(7), lightning-signpsbt(7).
+
+RESOURCES
+---------
+
+Main web site: <https://github.com/ElementsProject/lightning>

tests/test_wallet.py

@@ -813,6 +813,7 @@ def test_psbt_version(node_factory, bitcoind, chainparams):
         with pytest.raises(RpcError, match=r"Could not set PSBT version"):
             l1.rpc.setpsbtversion(v2_funding, i)
 
+
 @unittest.skipIf(TEST_NETWORK == 'liquid-regtest', 'Core/Elements need joinpsbt support for v2')
 def test_sign_and_send_psbt(node_factory, bitcoind, chainparams):
     """

wallet/walletrpc.c

@@ -813,6 +813,42 @@ static const struct json_command signpsbt_command = {
 
 AUTODATA(json_command, &signpsbt_command);
 
+static struct command_result *json_setpsbtversion(struct command *cmd,
+                        const char *buffer,
+					    const jsmntok_t *obj UNNEEDED,
+                        const jsmntok_t *params)
+{
+    struct json_stream *response;
+    unsigned int *version;
+    struct wally_psbt *psbt;
+
+    if (!param(cmd, buffer, params,
+           p_req("psbt", param_psbt, &psbt),
+           p_req("version", param_number, &version),
+           NULL))
+        return command_param_failed();
+
+    if (!psbt_set_version(psbt, *version)) {
+        return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+                    "Could not set PSBT version");
+    }
+
+    response = json_stream_success(cmd);
+    json_add_psbt(response, "psbt", psbt);
+
+    return command_success(cmd, response);
+}
+
+static const struct json_command setpsbtversion_command = {
+	"setpsbtversion",
+	"bitcoin",
+	json_setpsbtversion,
+	"Convert a given PSBT to the {version} requested (v0 or v2)",
+	false
+};
+
+AUTODATA(json_command, &setpsbtversion_command);
+
 struct sending_psbt {
 	struct command *cmd;
 	struct utxo **utxos;