chaintopology: new command 'parsefeerate'

Useful for parsing a passed in feerate before calling lightningd with
it, e.g. when you need to know what the feerate is for a fundpsbt before
calling fundpsbt

Changelog-Added: JSON-RPC: new command `parsefeerate` which takes a feerate string and returns the calculated perkw/perkb

doc/Makefile

@@ -54,6 +54,7 @@ MANPAGES := doc/lightning-cli.1 \
 	doc/lightning-openchannel_signed.7 \
 	doc/lightning-openchannel_update.7 \
 	doc/lightning-pay.7 \
+	doc/lightning-parsefeerate.7 \
 	doc/lightning-plugin.7 \
 	doc/lightning-reserveinputs.7 \
 	doc/lightning-sendinvoice.7 \

doc/index.rst

@@ -82,6 +82,7 @@ c-lightning Documentation
    lightning-openchannel_init <lightning-openchannel_init.7.md>
    lightning-openchannel_signed <lightning-openchannel_signed.7.md>
    lightning-openchannel_update <lightning-openchannel_update.7.md>
+   lightning-parsefeerate <lightning-parsefeerate.7.md>
    lightning-pay <lightning-pay.7.md>
    lightning-ping <lightning-ping.7.md>
    lightning-plugin <lightning-plugin.7.md>

doc/lightning-feerates.7

@@ -16,7 +16,6 @@ C-lightning will also smoothen feerate estimations from the backend\.
 
 \fIstyle\fR is either of the two strings:
 
-
 .RS
 .IP \[bu]
 \fIperkw\fR - provide feerate in units of satoshis per 1000 weight\.
@@ -27,7 +26,6 @@ C-lightning will also smoothen feerate estimations from the backend\.
 
 Bitcoin transactions have non-witness and witness bytes:
 
-
 .RS
 .IP \[bu]
 Non-witness bytes count as 4 weight, 1 virtual byte\.
@@ -58,7 +56,6 @@ which will override the recommended feerates returned by \fBfeerates\fR\.
 
 On success, an object is returned, containing:
 
-
 .RS
 .IP \[bu]
 \fBperkb\fR (object, optional): If \fIstyle\fR parameter was perkb:
@@ -125,7 +122,6 @@ On success, an object is returned, containing:
 
 The following warnings may also be returned:
 
-
 .RS
 .IP \[bu]
 \fBwarning_missing_feerates\fR: Some fee estimates are missing
@@ -143,7 +139,6 @@ Many other commands have a \fIfeerate\fR parameter, which can be the strings
 \fIurgent\fR, \fInormal\fR, or \fIslow\fR\.
 These are mapped to the \fBfeerates\fR outputs as:
 
-
 .RS
 .IP \[bu]
 \fIurgent\fR - equal to \fIunilateral_close\fR
@@ -167,11 +162,11 @@ manpage\.
 
 .SH SEE ALSO
 
-\fBlightning-fundchannel\fR(7), \fBlightning-withdraw\fR(7), \fBlightning-txprepare\fR(7),
-\fBlightning-fundchannel_start\fR(7)\.
+\fBlightning-parsefeerate\fR(7), \fBlightning-fundchannel\fR(7), \fBlightning-withdraw\fR(7),
+\fBlightning-txprepare\fR(7), \fBlightning-fundchannel_start\fR(7)\.
 
 .SH RESOURCES
 
 Main web site: \fIhttps://github.com/ElementsProject/lightning\fR
 
-\" SHA256STAMP:227e0f9f9b4d3c2b80d58466ed4fae768a5a2e7c2234e43105e21efc4a0b1861
+\" SHA256STAMP:3c68e2e2b47bc4107d71e263372b3ec3ac77434d7319c670f293d3be88703fe7

doc/lightning-feerates.7.md

@@ -110,8 +110,8 @@ manpage.
 SEE ALSO
 --------
 
-lightning-fundchannel(7), lightning-withdraw(7), lightning-txprepare(7),
-lightning-fundchannel_start(7).
+lightning-parsefeerate(7), lightning-fundchannel(7), lightning-withdraw(7),
+lightning-txprepare(7), lightning-fundchannel_start(7).
 
 RESOURCES
 ---------

doc/lightning-parsefeerate.7

@@ -0,0 +1,44 @@
+.TH "LIGHTNING-PARSEFEERATE" "7" "" "" "lightning-parsefeerate"
+.SH NAME
+lightning-parsefeerate - Command for parsing a feerate string to a feerate
+.SH SYNOPSIS
+
+\fBparsefeerate\fR \fIfeerate_str\fR
+
+.SH DESCRIPTION
+
+The \fBparsefeerate\fR command returns the current feerate for any valid
+\fIfeerate_str\fR\. This is useful for finding the current feerate that a
+\fBfundpsbt\fR or \fButxopsbt\fR command might use\.
+
+.SH RETURN VALUE
+
+On success, an object is returned, containing:
+
+.RS
+.IP \[bu]
+\fBperkw\fR (u32, optional): Value of \fIfeerate_str\fR in kilosipa
+
+.RE
+.SH ERRORS
+
+The \fBparsefeerate\fR command will error if the \fIfeerate_str\fR format is
+not recognized\.
+
+.RS
+.IP \[bu]
+-32602: If the given parameters are wrong\.
+
+.RE
+.SH TRIVIA
+
+In C-lightning we like to call the weight unit "sipa"
+in honor of Pieter Wuille,
+who uses the name "sipa" on IRC and elsewhere\.
+Internally we call the \fIperkw\fR style as "feerate per kilosipa"\.
+
+.SH RESOURCES
+
+Main web site: \fIhttps://github.com/ElementsProject/lightning\fR
+
+\" SHA256STAMP:1395d3fe85f6eb1f09c3706c50a9660dd9ade04e71435bde3fe1f9660f7b2655

doc/lightning-parsefeerate.7.md

@@ -0,0 +1,45 @@
+lightning-parsefeerate -- Command for parsing a feerate string to a feerate
+===========================================================================
+
+SYNOPSIS
+--------
+
+**parsefeerate** *feerate_str*
+
+DESCRIPTION
+-----------
+
+The **parsefeerate** command returns the current feerate for any valid
+*feerate_str*. This is useful for finding the current feerate that a
+**fundpsbt** or **utxopsbt** command might use.
+
+RETURN VALUE
+------------
+
+[comment]: # (GENERATE-FROM-SCHEMA-START)
+On success, an object is returned, containing:
+- **perkw** (u32, optional): Value of *feerate_str* in kilosipa
+[comment]: # (GENERATE-FROM-SCHEMA-END)
+
+ERRORS
+------
+
+The **parsefeerate** command will error if the *feerate_str* format is
+not recognized.
+
+- -32602: If the given parameters are wrong.
+
+TRIVIA
+------
+
+In C-lightning we like to call the weight unit "sipa"
+in honor of Pieter Wuille,
+who uses the name "sipa" on IRC and elsewhere.
+Internally we call the *perkw* style as "feerate per kilosipa".
+
+RESOURCES
+---------
+
+Main web site: <https://github.com/ElementsProject/lightning>
+
+[comment]: # ( SHA256STAMP:db3351466f8d2675cecf6f5909c1f3ff264b6ffa865b2d64eb02bf0b45a31a4d)

doc/schemas/parsefeerate.schema.json

@@ -0,0 +1,13 @@
+{
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "type": "object",
+    "additionalProperties": false,
+    "required": [ ],
+    "properties": {
+	"perkw": {
+	    "type": "u32",
+	    "description": "Value of *feerate_str* in kilosipa",
+	    "additionalProperties": false
+	}
+    }
+}

lightningd/chaintopology.c

@@ -553,6 +553,33 @@ static const struct json_command feerates_command = {
 };
 AUTODATA(json_command, &feerates_command);
 
+static struct command_result *json_parse_feerate(struct command *cmd,
+						 const char *buffer,
+						 const jsmntok_t *obj UNNEEDED,
+						 const jsmntok_t *params)
+{
+	struct json_stream *response;
+	u32 *feerate;
+
+	if (!param(cmd, buffer, params,
+		   p_req("feerate", param_feerate, &feerate),
+		   NULL))
+		return command_param_failed();
+
+	response = json_stream_success(cmd);
+	json_add_num(response, feerate_style_name(FEERATE_PER_KSIPA),
+		     feerate_to_style(*feerate, FEERATE_PER_KSIPA));
+	return command_success(cmd, response);
+}
+
+static const struct json_command parse_feerate_command = {
+	"parsefeerate",
+	"bitcoin",
+	json_parse_feerate,
+	"Return current feerate in perkw + perkb for given feerate string."
+};
+AUTODATA(json_command, &parse_feerate_command);
+
 static void next_updatefee_timer(struct chain_topology *topo)
 {
 	/* This takes care of its own lifetime. */

tests/test_misc.py

@@ -1462,6 +1462,11 @@ def test_feerates(node_factory):
     types = ["opening", "mutual_close", "unilateral_close", "delayed_to_us",
              "htlc_resolution", "penalty"]
 
+    # Try parsing the feerates, won't work because can't estimate
+    for t in types:
+        with pytest.raises(RpcError, match=r'Cannot estimate fees'):
+            feerate = l1.rpc.parsefeerate(t)
+
     # Query feerates (shouldn't give any!)
     wait_for(lambda: len(l1.rpc.feerates('perkw')['perkw']) == 2)
     feerates = l1.rpc.feerates('perkw')
@@ -1539,6 +1544,13 @@ def test_feerates(node_factory):
     htlc_feerate = feerates["perkw"]["htlc_resolution"]
     htlc_timeout_cost = feerates["onchain_fee_estimates"]["htlc_timeout_satoshis"]
     htlc_success_cost = feerates["onchain_fee_estimates"]["htlc_success_satoshis"]
+
+    # Try parsing the feerates, won't work because can't estimate
+    for t in types:
+        feerate = l1.rpc.parsefeerate(t)
+        assert feerate['perkw']
+        assert 'perkb' not in feerate
+
     if EXPERIMENTAL_FEATURES:
         # option_anchor_outputs
         assert htlc_timeout_cost == htlc_feerate * 666 // 1000