refactor: move uncompressed-permitted logic into ParsePubkey*

This is a preparation for parsing xonly pubkeys, which will complicate
this logic. It's cleaner to put the decision logic close to the public
key parsing itself.

Author: sipa

src/script/descriptor.cpp

@@ -821,9 +821,10 @@ class WSHDescriptor final : public DescriptorImpl
 ////////////////////////////////////////////////////////////////////////////
 
 enum class ParseScriptContext {
-    TOP,
-    P2SH,
-    P2WSH,
+    TOP,     //!< Top-level context (script goes directly in scriptPubKey)
+    P2SH,    //!< Inside sh() (script becomes P2SH redeemScript)
+    P2WPKH,  //!< Inside wpkh() (no script, pubkey only)
+    P2WSH,   //!< Inside wsh() (script becomes v0 witness script)
 };
 
 /** Parse a key path, being passed a split list of elements (the first element is ignored). */
@@ -850,10 +851,11 @@ enum class ParseScriptContext {
 }
 
 /** Parse a public key that excludes origin information. */
-std::unique_ptr<PubkeyProvider> ParsePubkeyInner(uint32_t key_exp_index, const Span<const char>& sp, bool permit_uncompressed, FlatSigningProvider& out, std::string& error)
+std::unique_ptr<PubkeyProvider> ParsePubkeyInner(uint32_t key_exp_index, const Span<const char>& sp, ParseScriptContext ctx, FlatSigningProvider& out, std::string& error)
 {
     using namespace spanparsing;
 
+    bool permit_uncompressed = ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH;
     auto split = Split(sp, '/');
     std::string str(split[0].begin(), split[0].end());
     if (str.size() == 0) {
@@ -911,7 +913,7 @@ std::unique_ptr<PubkeyProvider> ParsePubkeyInner(uint32_t key_exp_index, const S
 }
 
 /** Parse a public key including origin information (if enabled). */
-std::unique_ptr<PubkeyProvider> ParsePubkey(uint32_t key_exp_index, const Span<const char>& sp, bool permit_uncompressed, FlatSigningProvider& out, std::string& error)
+std::unique_ptr<PubkeyProvider> ParsePubkey(uint32_t key_exp_index, const Span<const char>& sp, ParseScriptContext ctx, FlatSigningProvider& out, std::string& error)
 {
     using namespace spanparsing;
 
@@ -920,7 +922,7 @@ std::unique_ptr<PubkeyProvider> ParsePubkey(uint32_t key_exp_index, const Span<c
         error = "Multiple ']' characters found for a single pubkey";
         return nullptr;
     }
-    if (origin_split.size() == 1) return ParsePubkeyInner(key_exp_index, origin_split[0], permit_uncompressed, out, error);
+    if (origin_split.size() == 1) return ParsePubkeyInner(key_exp_index, origin_split[0], ctx, out, error);
     if (origin_split[0].empty() || origin_split[0][0] != '[') {
         error = strprintf("Key origin start '[ character expected but not found, got '%c' instead",
                           origin_split[0].empty() ? /** empty, implies split char */ ']' : origin_split[0][0]);
@@ -942,7 +944,7 @@ std::unique_ptr<PubkeyProvider> ParsePubkey(uint32_t key_exp_index, const Span<c
     assert(fpr_bytes.size() == 4);
     std::copy(fpr_bytes.begin(), fpr_bytes.end(), info.fingerprint);
     if (!ParseKeyPath(slash_split, info.path, error)) return nullptr;
-    auto provider = ParsePubkeyInner(key_exp_index, origin_split[1], permit_uncompressed, out, error);
+    auto provider = ParsePubkeyInner(key_exp_index, origin_split[1], ctx, out, error);
     if (!provider) return nullptr;
     return std::make_unique<OriginPubkeyProvider>(key_exp_index, std::move(info), std::move(provider));
 }
@@ -955,19 +957,19 @@ std::unique_ptr<DescriptorImpl> ParseScript(uint32_t& key_exp_index, Span<const
     auto expr = Expr(sp);
     bool sorted_multi = false;
     if (Func("pk", expr)) {
-        auto pubkey = ParsePubkey(key_exp_index, expr, ctx != ParseScriptContext::P2WSH, out, error);
+        auto pubkey = ParsePubkey(key_exp_index, expr, ctx, out, error);
         if (!pubkey) return nullptr;
         ++key_exp_index;
         return std::make_unique<PKDescriptor>(std::move(pubkey));
     }
     if (Func("pkh", expr)) {
-        auto pubkey = ParsePubkey(key_exp_index, expr, ctx != ParseScriptContext::P2WSH, out, error);
+        auto pubkey = ParsePubkey(key_exp_index, expr, ctx, out, error);
         if (!pubkey) return nullptr;
         ++key_exp_index;
         return std::make_unique<PKHDescriptor>(std::move(pubkey));
     }
     if (ctx == ParseScriptContext::TOP && Func("combo", expr)) {
-        auto pubkey = ParsePubkey(key_exp_index, expr, true, out, error);
+        auto pubkey = ParsePubkey(key_exp_index, expr, ctx, out, error);
         if (!pubkey) return nullptr;
         ++key_exp_index;
         return std::make_unique<ComboDescriptor>(std::move(pubkey));
@@ -990,7 +992,7 @@ std::unique_ptr<DescriptorImpl> ParseScript(uint32_t& key_exp_index, Span<const
                 return nullptr;
             }
             auto arg = Expr(expr);
-            auto pk = ParsePubkey(key_exp_index, arg, ctx != ParseScriptContext::P2WSH, out, error);
+            auto pk = ParsePubkey(key_exp_index, arg, ctx, out, error);
             if (!pk) return nullptr;
             script_size += pk->GetSize() + 1;
             providers.emplace_back(std::move(pk));
@@ -1021,7 +1023,7 @@ std::unique_ptr<DescriptorImpl> ParseScript(uint32_t& key_exp_index, Span<const
         return std::make_unique<MultisigDescriptor>(thres, std::move(providers), sorted_multi);
     }
     if (ctx != ParseScriptContext::P2WSH && Func("wpkh", expr)) {
-        auto pubkey = ParsePubkey(key_exp_index, expr, false, out, error);
+        auto pubkey = ParsePubkey(key_exp_index, expr, ParseScriptContext::P2WPKH, out, error);
         if (!pubkey) return nullptr;
         key_exp_index++;
         return std::make_unique<WPKHDescriptor>(std::move(pubkey));