miniscript: introduce a MsContext() helper to contexts

We are going to introduce Tapscript support in Miniscript, for which
some of Miniscript rules and properties change (new or modified
fragments, different typing rules, different resources consumption, ..).

3 files changed, 21 insertions, 3 deletions

diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index 896fb0b5b3..eaef481c51 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -1426,8 +1426,11 @@ struct KeyParser {
     mutable std::vector<std::unique_ptr<PubkeyProvider>> m_keys;
     //! Used to detect key parsing errors within a Miniscript.
     mutable std::string m_key_parsing_error;
+    //! The script context we're operating within (Tapscript or P2WSH).
+    const miniscript::MiniscriptContext m_script_ctx;
 
-    KeyParser(FlatSigningProvider* out LIFETIMEBOUND, const SigningProvider* in LIFETIMEBOUND) : m_out(out), m_in(in) {}
+    KeyParser(FlatSigningProvider* out LIFETIMEBOUND, const SigningProvider* in LIFETIMEBOUND, miniscript::MiniscriptContext ctx)
+        : m_out(out), m_in(in), m_script_ctx(ctx) {}
 
     bool KeyCompare(const Key& a, const Key& b) const {
         return *m_keys.at(a) < *m_keys.at(b);
@@ -1475,6 +1478,10 @@ struct KeyParser {
         }
         return {};
     }
+
+    miniscript::MiniscriptContext MsContext() const {
+        return m_script_ctx;
+    }
 };
 
 /** Parse a script in a particular context. */
@@ -1714,7 +1721,7 @@ std::unique_ptr<DescriptorImpl> ParseScript(uint32_t& key_exp_index, Span<const
     }
     // Process miniscript expressions.
     {
-        KeyParser parser(&out, nullptr);
+        KeyParser parser(/*out = */&out, /* in = */nullptr, /* ctx = */miniscript::MiniscriptContext::P2WSH);
         auto node = miniscript::FromString(std::string(expr.begin(), expr.end()), parser);
         if (node) {
             if (ctx != ParseScriptContext::P2WSH) {
@@ -1887,7 +1894,7 @@ std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptCo
     }
 
     if (ctx == ParseScriptContext::P2WSH) {
-        KeyParser parser(nullptr, &provider);
+        KeyParser parser(/* out = */nullptr, /* in = */&provider, /* ctx = */miniscript::MiniscriptContext::P2WSH);
         auto node = miniscript::FromScript(script, parser);
         if (node && node->IsSane()) {
             return std::make_unique<MiniscriptDescriptor>(std::move(parser.m_keys), std::move(node));
diff --git a/src/script/miniscript.h b/src/script/miniscript.h
index 4effa5ce4e..635efeed44 100644
--- a/src/script/miniscript.h
+++ b/src/script/miniscript.h
@@ -229,6 +229,11 @@ enum class Availability {
     MAYBE,
 };
 
+enum class MiniscriptContext {
+    P2WSH,
+    TAPSCRIPT,
+};
+
 namespace internal {
 
 //! Helper function for Node::CalcType.
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 92b7ad50b5..92c42dfe25 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -404,6 +404,8 @@ struct Satisfier {
     SignatureData& m_sig_data;
     const BaseSignatureCreator& m_creator;
     const CScript& m_witness_script;
+    //! For now Miniscript is only available under P2WSH.
+    const miniscript::MiniscriptContext m_script_ctx{miniscript::MiniscriptContext::P2WSH};
 
     explicit Satisfier(const SigningProvider& provider LIFETIMEBOUND, SignatureData& sig_data LIFETIMEBOUND,
                        const BaseSignatureCreator& creator LIFETIMEBOUND,
@@ -466,6 +468,10 @@ struct Satisfier {
     miniscript::Availability SatHASH160(const std::vector<unsigned char>& hash, std::vector<unsigned char>& preimage) const {
         return MsLookupHelper(m_sig_data.hash160_preimages, hash, preimage);
     }
+
+    miniscript::MiniscriptContext MsContext() const {
+        return m_script_ctx;
+    }
 };
 
 bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreator& creator, const CScript& fromPubKey, SignatureData& sigdata)