//===- ASTDiff.h - AST differencing API -----------------------*- C++ -*- -===//
//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file specifies an interface that can be used to compare C++ syntax
// trees.
//
// We use the gumtree algorithm which combines a heuristic top-down search that
// is able to match large subtrees that are equivalent, with an optimal
// algorithm to match small subtrees.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFF_H
#define LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFF_H
#include "clang/Tooling/ASTDiff/ASTDiffInternal.h"
#include <optional>
namespace clang {
namespace diff {
enum ChangeKind {
None,
Delete, // (Src): delete node Src.
Update, // (Src, Dst): update the value of node Src to match Dst.
Insert, // (Src, Dst, Pos): insert Src as child of Dst at offset Pos.
Move, // (Src, Dst, Pos): move Src to be a child of Dst at offset Pos.
UpdateMove // Same as Move plus Update.
};
/// Represents a Clang AST node, alongside some additional information.
struct Node {
NodeId Parent, LeftMostDescendant, RightMostDescendant;
int Depth, Height, Shift = 0;
DynTypedNode ASTNode;
SmallVector<NodeId, 4> Children;
ChangeKind Change = None;
ASTNodeKind getType() const;
StringRef getTypeLabel() const;
bool isLeaf() const { return Children.empty(); }
std::optional<StringRef> getIdentifier() const;
std::optional<std::string> getQualifiedIdentifier() const;
};
/// SyntaxTree objects represent subtrees of the AST.
/// They can be constructed from any Decl or Stmt.
class SyntaxTree {
public:
/// Constructs a tree from a translation unit.
SyntaxTree(ASTContext &AST);
/// Constructs a tree from any AST node.
template <class T>
SyntaxTree(T *Node, ASTContext &AST)
: TreeImpl(std::make_unique<Impl>(this, Node, AST)) {}
SyntaxTree(SyntaxTree &&Other) = default;
~SyntaxTree();
const ASTContext &getASTContext() const;
StringRef getFilename() const;
int getSize() const;
NodeId getRootId() const;
using PreorderIterator = NodeId;
PreorderIterator begin() const;
PreorderIterator end() const;
const Node &getNode(NodeId Id) const;
int findPositionInParent(NodeId Id) const;
// Returns the starting and ending offset of the node in its source file.
std::pair<unsigned, unsigned> getSourceRangeOffsets(const Node &N) const;
/// Serialize the node attributes to a string representation. This should
/// uniquely distinguish nodes of the same kind. Note that this function just
/// returns a representation of the node value, not considering descendants.
std::string getNodeValue(NodeId Id) const;
std::string getNodeValue(const Node &Node) const;
class Impl;
std::unique_ptr<Impl> TreeImpl;
};
struct ComparisonOptions {
/// During top-down matching, only consider nodes of at least this height.
int MinHeight = 2;
/// During bottom-up matching, match only nodes with at least this value as
/// the ratio of their common descendants.
double MinSimilarity = 0.5;
/// Whenever two subtrees are matched in the bottom-up phase, the optimal
/// mapping is computed, unless the size of either subtrees exceeds this.
int MaxSize = 100;
bool StopAfterTopDown = false;
/// Returns false if the nodes should never be matched.
bool isMatchingAllowed(const Node &N1, const Node &N2) const {
return N1.getType().isSame(N2.getType());
}
};
class ASTDiff {
public:
ASTDiff(SyntaxTree &Src, SyntaxTree &Dst, const ComparisonOptions &Options);
~ASTDiff();
// Returns the ID of the node that is mapped to the given node in SourceTree.
NodeId getMapped(const SyntaxTree &SourceTree, NodeId Id) const;
class Impl;
private:
std::unique_ptr<Impl> DiffImpl;
};
} // end namespace diff
} // end namespace clang
#endif