From 6b91f7df96ddefc32a193161339b20c79c5e4eae Mon Sep 17 00:00:00 2001
From: Ava Chow <github@achow101.com>
Date: Mon, 12 Feb 2024 17:06:01 -0500
Subject: [PATCH] descriptors: Have GetPrivKey fill keys directly

Instead of GetPrivKey returning a key and having the caller fill the
FlatSigningProvider, have GetPrivKey take the FlatSigningProvider and
fill it by itself.

GetPrivKey is now changed to void as the caller no longer cares whether
it succeeds or fails.
---
 src/script/descriptor.cpp | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index 70294629670b02..e20677c05ff62e 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -212,7 +212,7 @@ struct PubkeyProvider
     virtual bool ToNormalizedString(const SigningProvider& arg, std::string& out, const DescriptorCache* cache = nullptr) const = 0;
 
     /** Derive a private key, if private data is available in arg. */
-    virtual bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const = 0;
+    virtual void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const = 0;
 
     /** Return the non-extended public key for this PubkeyProvider, if it has one. */
     virtual std::optional<CPubKey> GetRootPubKey() const = 0;
@@ -274,9 +274,9 @@ class OriginPubkeyProvider final : public PubkeyProvider
         }
         return true;
     }
-    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
     {
-        return m_provider->GetPrivKey(pos, arg, key);
+        m_provider->GetPrivKey(pos, arg, out);
     }
     std::optional<CPubKey> GetRootPubKey() const override
     {
@@ -332,9 +332,12 @@ class ConstPubkeyProvider final : public PubkeyProvider
         ret = ToString(StringType::PUBLIC);
         return true;
     }
-    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
     {
-        return arg.GetKey(m_pubkey.GetID(), key);
+        CKeyID id = m_pubkey.GetID();
+        CKey key;
+        if (!arg.GetKey(id, key)) return;
+        out.keys.emplace(id, key);
     }
     std::optional<CPubKey> GetRootPubKey() const override
     {
@@ -552,15 +555,14 @@ class BIP32PubkeyProvider final : public PubkeyProvider
         }
         return true;
     }
-    bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
+    void GetPrivKey(int pos, const SigningProvider& arg, FlatSigningProvider& out) const override
     {
         CExtKey extkey;
         CExtKey dummy;
-        if (!GetDerivedExtKey(arg, extkey, dummy)) return false;
-        if (m_derive == DeriveType::UNHARDENED && !extkey.Derive(extkey, pos)) return false;
-        if (m_derive == DeriveType::HARDENED && !extkey.Derive(extkey, pos | 0x80000000UL)) return false;
-        key = extkey.key;
-        return true;
+        if (!GetDerivedExtKey(arg, extkey, dummy)) return;
+        if (m_derive == DeriveType::UNHARDENED && !extkey.Derive(extkey, pos)) return;
+        if (m_derive == DeriveType::HARDENED && !extkey.Derive(extkey, pos | 0x80000000UL)) return;
+        out.keys.emplace(extkey.key.GetPubKey().GetID(), extkey.key);
     }
     std::optional<CPubKey> GetRootPubKey() const override
     {
@@ -747,8 +749,7 @@ class DescriptorImpl : public Descriptor
     {
         for (const auto& p : m_pubkey_args) {
             CKey key;
-            if (!p->GetPrivKey(pos, provider, key)) continue;
-            out.keys.emplace(key.GetPubKey().GetID(), key);
+            p->GetPrivKey(pos, provider, out);
         }
         for (const auto& arg : m_subdescriptor_args) {
             arg->ExpandPrivate(pos, provider, out);