1//===- ASTDiff.h - AST differencing API -----------------------*- C++ -*- -===//
2//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9//
10// This file specifies an interface that can be used to compare C++ syntax
11// trees.
12//
13// We use the gumtree algorithm which combines a heuristic top-down search that
14// is able to match large subtrees that are equivalent, with an optimal
15// algorithm to match small subtrees.
16//
17//===----------------------------------------------------------------------===//
18
19#ifndef LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFF_H
20#define LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFF_H
21
22#include "clang/Tooling/ASTDiff/ASTDiffInternal.h"
23#include <optional>
24
25namespace clang {
26namespace diff {
27
28enum ChangeKind {
29  None,
30  Delete,    // (Src): delete node Src.
31  Update,    // (Src, Dst): update the value of node Src to match Dst.
32  Insert,    // (Src, Dst, Pos): insert Src as child of Dst at offset Pos.
33  Move,      // (Src, Dst, Pos): move Src to be a child of Dst at offset Pos.
34  UpdateMove // Same as Move plus Update.
35};
36
37/// Represents a Clang AST node, alongside some additional information.
38struct Node {
39  NodeId Parent, LeftMostDescendant, RightMostDescendant;
40  int Depth, Height, Shift = 0;
41  DynTypedNode ASTNode;
42  SmallVector<NodeId, 4> Children;
43  ChangeKind Change = None;
44
45  ASTNodeKind getType() const;
46  StringRef getTypeLabel() const;
47  bool isLeaf() const { return Children.empty(); }
48  std::optional<StringRef> getIdentifier() const;
49  std::optional<std::string> getQualifiedIdentifier() const;
50};
51
52/// SyntaxTree objects represent subtrees of the AST.
53/// They can be constructed from any Decl or Stmt.
54class SyntaxTree {
55public:
56  /// Constructs a tree from a translation unit.
57  SyntaxTree(ASTContext &AST);
58  /// Constructs a tree from any AST node.
59  template <class T>
60  SyntaxTree(T *Node, ASTContext &AST)
61      : TreeImpl(std::make_unique<Impl>(this, Node, AST)) {}
62  SyntaxTree(SyntaxTree &&Other) = default;
63  ~SyntaxTree();
64
65  const ASTContext &getASTContext() const;
66  StringRef getFilename() const;
67
68  int getSize() const;
69  NodeId getRootId() const;
70  using PreorderIterator = NodeId;
71  PreorderIterator begin() const;
72  PreorderIterator end() const;
73
74  const Node &getNode(NodeId Id) const;
75  int findPositionInParent(NodeId Id) const;
76
77  // Returns the starting and ending offset of the node in its source file.
78  std::pair<unsigned, unsigned> getSourceRangeOffsets(const Node &N) const;
79
80  /// Serialize the node attributes to a string representation. This should
81  /// uniquely distinguish nodes of the same kind. Note that this function just
82  /// returns a representation of the node value, not considering descendants.
83  std::string getNodeValue(NodeId Id) const;
84  std::string getNodeValue(const Node &Node) const;
85
86  class Impl;
87  std::unique_ptr<Impl> TreeImpl;
88};
89
90struct ComparisonOptions {
91  /// During top-down matching, only consider nodes of at least this height.
92  int MinHeight = 2;
93
94  /// During bottom-up matching, match only nodes with at least this value as
95  /// the ratio of their common descendants.
96  double MinSimilarity = 0.5;
97
98  /// Whenever two subtrees are matched in the bottom-up phase, the optimal
99  /// mapping is computed, unless the size of either subtrees exceeds this.
100  int MaxSize = 100;
101
102  bool StopAfterTopDown = false;
103
104  /// Returns false if the nodes should never be matched.
105  bool isMatchingAllowed(const Node &N1, const Node &N2) const {
106    return N1.getType().isSame(N2.getType());
107  }
108};
109
110class ASTDiff {
111public:
112  ASTDiff(SyntaxTree &Src, SyntaxTree &Dst, const ComparisonOptions &Options);
113  ~ASTDiff();
114
115  // Returns the ID of the node that is mapped to the given node in SourceTree.
116  NodeId getMapped(const SyntaxTree &SourceTree, NodeId Id) const;
117
118  class Impl;
119
120private:
121  std::unique_ptr<Impl> DiffImpl;
122};
123
124} // end namespace diff
125} // end namespace clang
126
127#endif
128