feature(send): enable optional opt in to optimistic query param

payjoin/src/send/mod.rs

@@ -444,6 +444,7 @@ fn serialize_url(
     fee_contribution: Option<OutputAmountAndIndex>,
     min_fee_rate: FeeRate,
     version: &str,
+    opt_in_to_optimistic_merge: bool,
 ) -> Result<Url, url::ParseError> {
     let mut url = endpoint;
     url.query_pairs_mut().append_pair("v", version);
@@ -455,6 +456,9 @@ fn serialize_url(
             .append_pair("additionalfeeoutputindex", &index.to_string())
             .append_pair("maxadditionalfeecontribution", &amount.to_sat().to_string());
     }
+    if opt_in_to_optimistic_merge {
+        url.query_pairs_mut().append_pair("optimisticmerge", "1");
+    }
     if min_fee_rate > FeeRate::ZERO {
         // TODO serialize in rust-bitcoin <https://github.com/rust-bitcoin/rust-bitcoin/pull/1787/files#diff-c2ea40075e93ccd068673873166cfa3312ec7439d6bc5a4cbc03e972c7e045c4>
         let float_fee_rate = min_fee_rate.to_sat_per_kwu() as f32 / 250.0_f32;

payjoin/src/send/v1.rs

@@ -253,6 +253,7 @@ impl Sender {
             self.fee_contribution,
             self.min_fee_rate,
             "1", // payjoin version
+            false, // Opt into optimistic multiparty payjoin
         )?;
         let body = self.psbt.to_string().as_bytes().to_vec();
         Ok((

payjoin/src/send/v2/mod.rs

@@ -67,6 +67,7 @@ impl<'a> SenderBuilder<'a> {
         Ok(Sender {
             v1: self.0.build_recommended(min_fee_rate)?,
             reply_key: HpkeKeyPair::gen_keypair().0,
+            opt_in_to_optimistic_merge: false,
         })
     }
 
@@ -107,6 +108,7 @@ impl<'a> SenderBuilder<'a> {
                 min_fee_rate,
                 clamp_fee_contribution,
             )?,
+            opt_in_to_optimistic_merge: false,
             reply_key: HpkeKeyPair::gen_keypair().0,
         })
     }
@@ -122,6 +124,7 @@ impl<'a> SenderBuilder<'a> {
         Ok(Sender {
             v1: self.0.build_non_incentivizing(min_fee_rate)?,
             reply_key: HpkeKeyPair::gen_keypair().0,
+            opt_in_to_optimistic_merge: false,
         })
     }
 }
@@ -132,6 +135,8 @@ pub struct Sender {
     v1: v1::Sender,
     /// The secret key to decrypt the receiver's reply.
     reply_key: HpkeSecretKey,
+    /// Allow for optimistic merge
+    opt_in_to_optimistic_merge: bool,
 }
 
 impl Sender {
@@ -164,6 +169,7 @@ impl Sender {
             self.v1.disable_output_substitution,
             self.v1.fee_contribution,
             self.v1.min_fee_rate,
+            self.opt_in_to_optimistic_merge,
         )?;
         let hpke_ctx = HpkeContext::new(rs, &self.reply_key);
         let body = encrypt_message_a(
@@ -210,6 +216,7 @@ fn serialize_v2_body(
     disable_output_substitution: bool,
     fee_contribution: Option<(bitcoin::Amount, usize)>,
     min_feerate: FeeRate,
+    opt_in_to_optimistic_merge: bool,
 ) -> Result<Vec<u8>, CreateRequestError> {
     // Grug say localhost base be discarded anyway. no big brain needed.
     let placeholder_url = serialize_url(
@@ -218,6 +225,7 @@ fn serialize_v2_body(
         fee_contribution,
         min_feerate,
         "2", // payjoin version
+        opt_in_to_optimistic_merge,
     )
     .map_err(InternalCreateRequestError::Url)?;
     let query_params = placeholder_url.query().unwrap_or_default();
@@ -349,6 +357,7 @@ mod test {
                 payee: ScriptBuf::from(vec![0x00]),
             },
             reply_key: HpkeKeyPair::gen_keypair().0,
+            opt_in_to_optimistic_merge: false,
         };
         let serialized = serde_json::to_string(&req_ctx).unwrap();
         let deserialized = serde_json::from_str(&serialized).unwrap();

payjoin/tests/integration.rs

@@ -181,7 +181,7 @@ mod integration {
         use http::StatusCode;
         use payjoin::send::v2::SenderBuilder;
         use payjoin::receive::v2::{
-            MultiPartyProposal, PayjoinProposal, Receiver, UnMergedMultiPartyProposal,
+            PayjoinProposal, Receiver, UnMergedMultiPartyProposal,
             UncheckedProposal,
         };
         use payjoin::{HpkeKeyPair, OhttpKeys, PjUri, UriExt};
@@ -409,6 +409,7 @@ mod integration {
                         .build_with_multiple_senders()?;
                 let (Request { url, body, content_type, .. }, send_post_ctx_1) =
                     sender_ctx_1.extract_v2(directory.to_owned())?;
+
                 let response = agent
                     .post(url.clone())
                     .header("Content-Type", content_type)
@@ -419,6 +420,7 @@ mod integration {
                 assert!(response.status().is_success());
                 let sender_get_ctx_1 = send_post_ctx_1
                     .process_response(&mut response.bytes().await?.to_vec().as_slice())?;
+
                 //**********************
                 // Inside Sender 2
                 // Sender 2 will POST a different psbt to the same subdir id