Abstract out EvalDescriptorStringOrObject from scantxoutset

src/rpc/blockchain.cpp

@@ -2241,43 +2241,14 @@ UniValue scantxoutset(const JSONRPCRequest& request)
 
         // loop through the scan objects
         for (const UniValue& scanobject : request.params[1].get_array().getValues()) {
-            std::string desc_str;
-            std::pair<int64_t, int64_t> range = {0, 1000};
-            if (scanobject.isStr()) {
-                desc_str = scanobject.get_str();
-            } else if (scanobject.isObject()) {
-                UniValue desc_uni = find_value(scanobject, "desc");
-                if (desc_uni.isNull()) throw JSONRPCError(RPC_INVALID_PARAMETER, "Descriptor needs to be provided in scan object");
-                desc_str = desc_uni.get_str();
-                UniValue range_uni = find_value(scanobject, "range");
-                if (!range_uni.isNull()) {
-                    range = ParseDescriptorRange(range_uni);
-                }
-            } else {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, "Scan object needs to be either a string or an object");
-            }
-
             FlatSigningProvider provider;
-            auto desc = Parse(desc_str, provider);
-            if (!desc) {
-                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Invalid descriptor '%s'", desc_str));
-            }
-            if (!desc->IsRange()) {
-                range.first = 0;
-                range.second = 0;
-            }
-            for (int i = range.first; i <= range.second; ++i) {
-                std::vector<CScript> scripts;
-                if (!desc->Expand(i, provider, scripts, provider)) {
-                    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Cannot derive script without private keys: '%s'", desc_str));
-                }
+            auto scripts = EvalDescriptorStringOrObject(scanobject, provider);
             for (const auto& script : scripts) {
                 std::string inferred = InferDescriptor(script, provider)->ToString();
                 needles.emplace(script);
                 descriptors.emplace(std::move(script), std::move(inferred));
             }
         }
-        }
 
         // Scan the unspent transaction output set for inputs
         UniValue unspents(UniValue::VARR);

src/rpc/util.cpp

@@ -5,6 +5,7 @@
 #include <key_io.h>
 #include <keystore.h>
 #include <rpc/util.h>
+#include <script/descriptor.h>
 #include <tinyformat.h>
 #include <util/strencodings.h>
 
@@ -685,3 +686,40 @@ std::pair<int64_t, int64_t> ParseDescriptorRange(const UniValue& value)
     }
     return {low, high};
 }
+
+std::vector<CScript> EvalDescriptorStringOrObject(const UniValue& scanobject, FlatSigningProvider& provider)
+{
+    std::string desc_str;
+    std::pair<int64_t, int64_t> range = {0, 1000};
+    if (scanobject.isStr()) {
+        desc_str = scanobject.get_str();
+    } else if (scanobject.isObject()) {
+        UniValue desc_uni = find_value(scanobject, "desc");
+        if (desc_uni.isNull()) throw JSONRPCError(RPC_INVALID_PARAMETER, "Descriptor needs to be provided in scan object");
+        desc_str = desc_uni.get_str();
+        UniValue range_uni = find_value(scanobject, "range");
+        if (!range_uni.isNull()) {
+            range = ParseDescriptorRange(range_uni);
+        }
+    } else {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "Scan object needs to be either a string or an object");
+    }
+
+    auto desc = Parse(desc_str, provider);
+    if (!desc) {
+        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Invalid descriptor '%s'", desc_str));
+    }
+    if (!desc->IsRange()) {
+        range.first = 0;
+        range.second = 0;
+    }
+    std::vector<CScript> ret;
+    for (int i = range.first; i <= range.second; ++i) {
+        std::vector<CScript> scripts;
+        if (!desc->Expand(i, provider, scripts, provider)) {
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, strprintf("Cannot derive script without private keys: '%s'", desc_str));
+        }
+        std::move(scripts.begin(), scripts.end(), std::back_inserter(ret));
+    }
+    return ret;
+}

src/rpc/util.h

@@ -8,6 +8,8 @@
 #include <node/transaction.h>
 #include <pubkey.h>
 #include <rpc/protocol.h>
+#include <script/script.h>
+#include <script/sign.h>
 #include <script/standard.h>
 #include <univalue.h>
 
@@ -83,6 +85,9 @@ UniValue JSONRPCTransactionError(TransactionError terr, const std::string& err_s
 //! Parse a JSON range specified as int64, or [int64, int64]
 std::pair<int64_t, int64_t> ParseDescriptorRange(const UniValue& value);
 
+/** Evaluate a descriptor given as a string, or as a {"desc":...,"range":...} object, with default range of 1000. */
+std::vector<CScript> EvalDescriptorStringOrObject(const UniValue& scanobject, FlatSigningProvider& provider);
+
 struct RPCArg {
     enum class Type {
         OBJ,