Add function selector to FunctionDefinition AST JSON

Changelog.md

@@ -38,6 +38,7 @@ Language Features:
  * Introduce ``virtual`` and ``override`` keywords.
  * Modify ``push(element)`` for dynamic storage arrays such that it does not return the new length anymore.
  * Yul: Introduce ``leave`` statement that exits the current function.
+ * JSON AST: Add the function selector of each externally-visible FunctonDefinition to the AST JSON export.
 
 Compiler Features:
  * Allow revert strings to be stripped from the binary using the ``--revert-strings`` option or the ``settings.debug.revertStrings`` setting.

libsolidity/ast/AST.cpp

@@ -368,6 +368,11 @@ string FunctionDefinition::externalSignature() const
 	return TypeProvider::function(*this)->externalSignature();
 }
 
+string FunctionDefinition::externalIdentifierHex() const
+{
+	return TypeProvider::function(*this)->externalIdentifierHex();
+}
+
 FunctionDefinitionAnnotation& FunctionDefinition::annotation() const
 {
 	if (!m_annotation)
@@ -596,6 +601,12 @@ set<VariableDeclaration::Location> VariableDeclaration::allowedDataLocations() c
 		return set<Location>{ Location::Unspecified };
 }
 
+string VariableDeclaration::externalIdentifierHex() const
+{
+	solAssert(isStateVariable() && isPublic(), "Can only be called for public state variables");
+	return TypeProvider::function(*this)->externalIdentifierHex();
+}
+
 TypePointer VariableDeclaration::type() const
 {
 	return annotation().type;

libsolidity/ast/AST.h

@@ -708,6 +708,9 @@ public:
 	/// arguments separated by commas all enclosed in parentheses without any spaces.
 	std::string externalSignature() const;
 
+	/// @returns the external identifier of this function (the hash of the signature) as a hex string.
+	std::string externalIdentifierHex() const;
+
 	ContractDefinition::ContractKind inContractKind() const;
 
 	TypePointer type() const override;
@@ -807,6 +810,9 @@ public:
 	/// @returns a set of allowed storage locations for the variable.
 	std::set<Location> allowedDataLocations() const;
 
+	/// @returns the external identifier of this variable (the hash of the signature) as a hex string (works only for public state variables).
+	std::string externalIdentifierHex() const;
+
 	TypePointer type() const override;
 
 	/// @param _internal false indicates external interface is concerned, true indicates internal interface is concerned.

libsolidity/ast/ASTJsonConverter.cpp

@@ -362,6 +362,8 @@ bool ASTJsonConverter::visit(FunctionDefinition const& _node)
 		make_pair("implemented", _node.isImplemented()),
 		make_pair("scope", idOrNull(_node.scope()))
 	};
+	if (_node.isPartOfExternalInterface())
+		attributes.emplace_back("functionSelector", _node.externalIdentifierHex());
 	if (!_node.annotation().baseFunctions.empty())
 		attributes.emplace_back(make_pair("baseFunctions", getContainerIds(_node.annotation().baseFunctions, true)));
 	if (m_legacy)
@@ -384,6 +386,8 @@ bool ASTJsonConverter::visit(VariableDeclaration const& _node)
 		make_pair("scope", idOrNull(_node.scope())),
 		make_pair("typeDescriptions", typePointerToJson(_node.annotation().type, true))
 	};
+	if (_node.isStateVariable() && _node.isPublic())
+		attributes.emplace_back("functionSelector", _node.externalIdentifierHex());
 	if (m_inEvent)
 		attributes.emplace_back("indexed", _node.isIndexed());
 	if (!_node.annotation().baseFunctions.empty())

libsolidity/ast/Types.cpp

@@ -3191,6 +3191,11 @@ u256 FunctionType::externalIdentifier() const
 	return FixedHash<4>::Arith(FixedHash<4>(dev::keccak256(externalSignature())));
 }
 
+string FunctionType::externalIdentifierHex() const
+{
+	return FixedHash<4>(dev::keccak256(externalSignature())).hex();
+}
+
 bool FunctionType::isPure() const
 {
 	// TODO: replace this with m_stateMutability == StateMutability::Pure once

libsolidity/ast/Types.h

@@ -1190,6 +1190,8 @@ public:
 	std::string externalSignature() const;
 	/// @returns the external identifier of this function (the hash of the signature).
 	u256 externalIdentifier() const;
+	/// @returns the external identifier of this function (the hash of the signature) as a hex string.
+	std::string externalIdentifierHex() const;
 	Declaration const& declaration() const
 	{
 		solAssert(m_declaration, "Requested declaration from a FunctionType that has none");