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(Other: 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

source code of clang/include/clang/Tooling/ASTDiff/ASTDiff.h