//===--- Transformer.h - Transformer class ----------------------*- 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
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_TOOLING_TRANSFORMER_TRANSFORMER_H_
#define LLVM_CLANG_TOOLING_TRANSFORMER_TRANSFORMER_H_
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Tooling/Refactoring/AtomicChange.h"
#include "clang/Tooling/Transformer/RewriteRule.h"
#include "llvm/Support/Error.h"
#include <functional>
#include <utility>
namespace clang {
namespace tooling {
namespace detail {
/// Implementation details of \c Transformer with type erasure around
/// \c RewriteRule<T> as well as the corresponding consumers.
class TransformerImpl {
public:
virtual ~TransformerImpl() = default;
void onMatch(const ast_matchers::MatchFinder::MatchResult &Result);
virtual std::vector<ast_matchers::internal::DynTypedMatcher>
buildMatchers() const = 0;
protected:
/// Converts a set of \c Edit into a \c AtomicChange per file modified.
/// Returns an error if the edits fail to compose, e.g. overlapping edits.
static llvm::Expected<llvm::SmallVector<AtomicChange, 1>>
convertToAtomicChanges(const llvm::SmallVectorImpl<transformer::Edit> &Edits,
const ast_matchers::MatchFinder::MatchResult &Result);
private:
virtual void
onMatchImpl(const ast_matchers::MatchFinder::MatchResult &Result) = 0;
};
// FIXME: Use std::type_identity or backport when available.
template <class T> struct type_identity {
using type = T;
};
} // namespace detail
template <typename T> struct TransformerResult {
llvm::MutableArrayRef<AtomicChange> Changes;
T Metadata;
};
template <> struct TransformerResult<void> {
llvm::MutableArrayRef<AtomicChange> Changes;
};
/// Handles the matcher and callback registration for a single `RewriteRule`, as
/// defined by the arguments of the constructor.
class Transformer : public ast_matchers::MatchFinder::MatchCallback {
public:
/// Provides the set of changes to the consumer. The callback is free to move
/// or destructively consume the changes as needed.
///
/// We use \c MutableArrayRef as an abstraction to provide decoupling, and we
/// expect the majority of consumers to copy or move the individual values
/// into a separate data structure.
using ChangeSetConsumer = std::function<void(
Expected<llvm::MutableArrayRef<AtomicChange>> Changes)>;
/// \param Consumer receives all rewrites for a single match, or an error.
/// Will not necessarily be called for each match; for example, if the rule
/// generates no edits but does not fail. Note that clients are responsible
/// for handling the case that independent \c AtomicChanges conflict with each
/// other.
explicit Transformer(transformer::RewriteRuleWith<void> Rule,
ChangeSetConsumer Consumer)
: Transformer(std::move(Rule),
[Consumer = std::move(Consumer)](
llvm::Expected<TransformerResult<void>> Result) {
if (Result)
Consumer(Result->Changes);
else
Consumer(Result.takeError());
}) {}
/// \param Consumer receives all rewrites and the associated metadata for a
/// single match, or an error. Will always be called for each match, even if
/// the rule generates no edits. Note that clients are responsible for
/// handling the case that independent \c AtomicChanges conflict with each
/// other.
template <typename MetadataT>
explicit Transformer(
transformer::RewriteRuleWith<MetadataT> Rule,
std::function<void(llvm::Expected<TransformerResult<
typename detail::type_identity<MetadataT>::type>>)>
Consumer);
/// N.B. Passes `this` pointer to `MatchFinder`. So, this object should not
/// be moved after this call.
void registerMatchers(ast_matchers::MatchFinder *MatchFinder);
/// Not called directly by users -- called by the framework, via base class
/// pointer.
void run(const ast_matchers::MatchFinder::MatchResult &Result) override;
private:
std::unique_ptr<detail::TransformerImpl> Impl;
};
namespace detail {
/// Runs the metadata generator on \c Rule and stuffs it into \c Result.
/// @{
template <typename T>
llvm::Error
populateMetadata(const transformer::RewriteRuleWith<T> &Rule,
size_t SelectedCase,
const ast_matchers::MatchFinder::MatchResult &Match,
TransformerResult<T> &Result) {
// Silence a false positive GCC -Wunused-but-set-parameter warning in constexpr
// cases, by marking SelectedCase as used. See
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85827 for details. The issue is
// fixed in GCC 10.
(void)SelectedCase;
if constexpr (!std::is_void_v<T>) {
auto Metadata = Rule.Metadata[SelectedCase]->eval(Match);
if (!Metadata)
return Metadata.takeError();
Result.Metadata = std::move(*Metadata);
}
return llvm::Error::success();
}
/// @}
/// Implementation when metadata is generated as a part of the rewrite. This
/// happens when we have a \c RewriteRuleWith<T>.
template <typename T> class WithMetadataImpl final : public TransformerImpl {
transformer::RewriteRuleWith<T> Rule;
std::function<void(llvm::Expected<TransformerResult<T>>)> Consumer;
public:
explicit WithMetadataImpl(
transformer::RewriteRuleWith<T> R,
std::function<void(llvm::Expected<TransformerResult<T>>)> Consumer)
: Rule(std::move(R)), Consumer(std::move(Consumer)) {
assert(llvm::all_of(Rule.Cases,
[](const transformer::RewriteRuleBase::Case &Case)
-> bool { return !!Case.Edits; }) &&
"edit generator must be provided for each rule");
if constexpr (!std::is_void_v<T>)
assert(llvm::all_of(Rule.Metadata,
[](const typename transformer::Generator<T> &Metadata)
-> bool { return !!Metadata; }) &&
"metadata generator must be provided for each rule");
}
private:
void onMatchImpl(const ast_matchers::MatchFinder::MatchResult &Result) final {
size_t I = transformer::detail::findSelectedCase(Result, Rule);
auto Transformations = Rule.Cases[I].Edits(Result);
if (!Transformations) {
Consumer(Transformations.takeError());
return;
}
llvm::SmallVector<AtomicChange, 1> Changes;
if (!Transformations->empty()) {
auto C = convertToAtomicChanges(*Transformations, Result);
if (C) {
Changes = std::move(*C);
} else {
Consumer(C.takeError());
return;
}
} else if (std::is_void<T>::value) {
// If we don't have metadata and we don't have any edits, skip.
return;
}
TransformerResult<T> RewriteResult;
if (auto E = populateMetadata(Rule, I, Result, RewriteResult)) {
Consumer(std::move(E));
return;
}
RewriteResult.Changes = llvm::MutableArrayRef<AtomicChange>(Changes);
Consumer(std::move(RewriteResult));
}
std::vector<ast_matchers::internal::DynTypedMatcher>
buildMatchers() const final {
return transformer::detail::buildMatchers(Rule);
}
};
} // namespace detail
template <typename MetadataT>
Transformer::Transformer(
transformer::RewriteRuleWith<MetadataT> Rule,
std::function<void(llvm::Expected<TransformerResult<
typename detail::type_identity<MetadataT>::type>>)>
Consumer)
: Impl(std::make_unique<detail::WithMetadataImpl<MetadataT>>(
std::move(Rule), std::move(Consumer))) {}
} // namespace tooling
} // namespace clang
#endif // LLVM_CLANG_TOOLING_TRANSFORMER_TRANSFORMER_H_