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//===--- JSON.h - JSON values, parsing and serialization -------*- 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
//
//===---------------------------------------------------------------------===//
///
/// \file
/// This file supports working with JSON data.
///
/// It comprises:
///
/// - classes which hold dynamically-typed parsed JSON structures
/// These are value types that can be composed, inspected, and modified.
/// See json::Value, and the related types json::Object and json::Array.
///
/// - functions to parse JSON text into Values, and to serialize Values to text.
/// See parse(), operator<<, and format_provider.
///
/// - a convention and helpers for mapping between json::Value and user-defined
/// types. See fromJSON(), ObjectMapper, and the class comment on Value.
///
/// - an output API json::OStream which can emit JSON without materializing
/// all structures as json::Value.
///
/// Typically, JSON data would be read from an external source, parsed into
/// a Value, and then converted into some native data structure before doing
/// real work on it. (And vice versa when writing).
///
/// Other serialization mechanisms you may consider:
///
/// - YAML is also text-based, and more human-readable than JSON. It's a more
/// complex format and data model, and YAML parsers aren't ubiquitous.
/// YAMLParser.h is a streaming parser suitable for parsing large documents
/// (including JSON, as YAML is a superset). It can be awkward to use
/// directly. YAML I/O (YAMLTraits.h) provides data mapping that is more
/// declarative than the toJSON/fromJSON conventions here.
///
/// - LLVM bitstream is a space- and CPU- efficient binary format. Typically it
/// encodes LLVM IR ("bitcode"), but it can be a container for other data.
/// Low-level reader/writer libraries are in Bitstream/Bitstream*.h
///
//===---------------------------------------------------------------------===//
#ifndef LLVM_SUPPORT_JSON_H
#define LLVM_SUPPORT_JSON_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLFunctionalExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/raw_ostream.h"
#include <cmath>
#include <map>
namespace llvm {
namespace json {
// === String encodings ===
//
// JSON strings are character sequences (not byte sequences like std::string).
// We need to know the encoding, and for simplicity only support UTF-8.
//
// - When parsing, invalid UTF-8 is a syntax error like any other
//
// - When creating Values from strings, callers must ensure they are UTF-8.
// with asserts on, invalid UTF-8 will crash the program
// with asserts off, we'll substitute the replacement character (U+FFFD)
// Callers can use json::isUTF8() and json::fixUTF8() for validation.
//
// - When retrieving strings from Values (e.g. asString()), the result will
// always be valid UTF-8.
template <typename T>
constexpr bool is_uint_64_bit_v =
std::is_integral_v<T> && std::is_unsigned_v<T> &&
sizeof(T) == sizeof(uint64_t);
/// Returns true if \p S is valid UTF-8, which is required for use as JSON.
/// If it returns false, \p Offset is set to a byte offset near the first error.
bool isUTF8(llvm::StringRef S, size_t *ErrOffset = nullptr);
/// Replaces invalid UTF-8 sequences in \p S with the replacement character
/// (U+FFFD). The returned string is valid UTF-8.
/// This is much slower than isUTF8, so test that first.
std::string fixUTF8(llvm::StringRef S);
class Array;
class ObjectKey;
class Value;
template <typename T> Value toJSON(const std::optional<T> &Opt);
/// An Object is a JSON object, which maps strings to heterogenous JSON values.
/// It simulates DenseMap<ObjectKey, Value>. ObjectKey is a maybe-owned string.
class Object {
using Storage = DenseMap<ObjectKey, Value, llvm::DenseMapInfo<StringRef>>;
Storage M;
public:
using key_type = ObjectKey;
using mapped_type = Value;
using value_type = Storage::value_type;
using iterator = Storage::iterator;
using const_iterator = Storage::const_iterator;
Object() = default;
// KV is a trivial key-value struct for list-initialization.
// (using std::pair forces extra copies).
struct KV;
explicit Object(std::initializer_list<KV> Properties);
iterator begin() { return M.begin(); }
const_iterator begin() const { return M.begin(); }
iterator end() { return M.end(); }
const_iterator end() const { return M.end(); }
bool empty() const { return M.empty(); }
size_t size() const { return M.size(); }
void clear() { M.clear(); }
std::pair<iterator, bool> insert(KV E);
template <typename... Ts>
std::pair<iterator, bool> try_emplace(const ObjectKey &K, Ts &&... Args) {
return M.try_emplace(K, std::forward<Ts>(Args)...);
}
template <typename... Ts>
std::pair<iterator, bool> try_emplace(ObjectKey &&K, Ts &&... Args) {
return M.try_emplace(std::move(K), std::forward<Ts>(Args)...);
}
bool erase(StringRef K);
void erase(iterator I) { M.erase(I); }
iterator find(StringRef K) { return M.find_as(K); }
const_iterator find(StringRef K) const { return M.find_as(K); }
// operator[] acts as if Value was default-constructible as null.
Value &operator[](const ObjectKey &K);
Value &operator[](ObjectKey &&K);
// Look up a property, returning nullptr if it doesn't exist.
Value *get(StringRef K);
const Value *get(StringRef K) const;
// Typed accessors return std::nullopt/nullptr if
// - the property doesn't exist
// - or it has the wrong type
std::optional<std::nullptr_t> getNull(StringRef K) const;
std::optional<bool> getBoolean(StringRef K) const;
std::optional<double> getNumber(StringRef K) const;
std::optional<int64_t> getInteger(StringRef K) const;
std::optional<llvm::StringRef> getString(StringRef K) const;
const json::Object *getObject(StringRef K) const;
json::Object *getObject(StringRef K);
const json::Array *getArray(StringRef K) const;
json::Array *getArray(StringRef K);
};
bool operator==(const Object &LHS, const Object &RHS);
inline bool operator!=(const Object &LHS, const Object &RHS) {
return !(LHS == RHS);
}
/// An Array is a JSON array, which contains heterogeneous JSON values.
/// It simulates std::vector<Value>.
class Array {
std::vector<Value> V;
public:
using value_type = Value;
using iterator = std::vector<Value>::iterator;
using const_iterator = std::vector<Value>::const_iterator;
Array() = default;
explicit Array(std::initializer_list<Value> Elements);
template <typename Collection> explicit Array(const Collection &C) {
for (const auto &V : C)
emplace_back(V);
}
Value &operator[](size_t I);
const Value &operator[](size_t I) const;
Value &front();
const Value &front() const;
Value &back();
const Value &back() const;
Value *data();
const Value *data() const;
iterator begin();
const_iterator begin() const;
iterator end();
const_iterator end() const;
bool empty() const;
size_t size() const;
void reserve(size_t S);
void clear();
void push_back(const Value &E);
void push_back(Value &&E);
template <typename... Args> void emplace_back(Args &&...A);
void pop_back();
iterator insert(const_iterator P, const Value &E);
iterator insert(const_iterator P, Value &&E);
template <typename It> iterator insert(const_iterator P, It A, It Z);
template <typename... Args> iterator emplace(const_iterator P, Args &&...A);
friend bool operator==(const Array &L, const Array &R);
};
inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }
/// A Value is an JSON value of unknown type.
/// They can be copied, but should generally be moved.
///
/// === Composing values ===
///
/// You can implicitly construct Values from:
/// - strings: std::string, SmallString, formatv, StringRef, char*
/// (char*, and StringRef are references, not copies!)
/// - numbers
/// - booleans
/// - null: nullptr
/// - arrays: {"foo", 42.0, false}
/// - serializable things: types with toJSON(const T&)->Value, found by ADL
///
/// They can also be constructed from object/array helpers:
/// - json::Object is a type like map<ObjectKey, Value>
/// - json::Array is a type like vector<Value>
/// These can be list-initialized, or used to build up collections in a loop.
/// json::ary(Collection) converts all items in a collection to Values.
///
/// === Inspecting values ===
///
/// Each Value is one of the JSON kinds:
/// null (nullptr_t)
/// boolean (bool)
/// number (double, int64 or uint64)
/// string (StringRef)
/// array (json::Array)
/// object (json::Object)
///
/// The kind can be queried directly, or implicitly via the typed accessors:
/// if (std::optional<StringRef> S = E.getAsString()
/// assert(E.kind() == Value::String);
///
/// Array and Object also have typed indexing accessors for easy traversal:
/// Expected<Value> E = parse(R"( {"options": {"font": "sans-serif"}} )");
/// if (Object* O = E->getAsObject())
/// if (Object* Opts = O->getObject("options"))
/// if (std::optional<StringRef> Font = Opts->getString("font"))
/// assert(Opts->at("font").kind() == Value::String);
///
/// === Converting JSON values to C++ types ===
///
/// The convention is to have a deserializer function findable via ADL:
/// fromJSON(const json::Value&, T&, Path) -> bool
///
/// The return value indicates overall success, and Path is used for precise
/// error reporting. (The Path::Root passed in at the top level fromJSON call
/// captures any nested error and can render it in context).
/// If conversion fails, fromJSON calls Path::report() and immediately returns.
/// This ensures that the first fatal error survives.
///
/// Deserializers are provided for:
/// - bool
/// - int and int64_t
/// - double
/// - std::string
/// - vector<T>, where T is deserializable
/// - map<string, T>, where T is deserializable
/// - std::optional<T>, where T is deserializable
/// ObjectMapper can help writing fromJSON() functions for object types.
///
/// For conversion in the other direction, the serializer function is:
/// toJSON(const T&) -> json::Value
/// If this exists, then it also allows constructing Value from T, and can
/// be used to serialize vector<T>, map<string, T>, and std::optional<T>.
///
/// === Serialization ===
///
/// Values can be serialized to JSON:
/// 1) raw_ostream << Value // Basic formatting.
/// 2) raw_ostream << formatv("{0}", Value) // Basic formatting.
/// 3) raw_ostream << formatv("{0:2}", Value) // Pretty-print with indent 2.
///
/// And parsed:
/// Expected<Value> E = json::parse("[1, 2, null]");
/// assert(E && E->kind() == Value::Array);
class Value {
public:
enum Kind {
Null,
Boolean,
/// Number values can store both int64s and doubles at full precision,
/// depending on what they were constructed/parsed from.
Number,
String,
Array,
Object,
};
// It would be nice to have Value() be null. But that would make {} null too.
Value(const Value &M) { copyFrom(M); }
Value(Value &&M) { moveFrom(std::move(M)); }
Value(std::initializer_list<Value> Elements);
Value(json::Array &&Elements) : Type(T_Array) {
create<json::Array>(std::move(Elements));
}
template <typename Elt>
Value(const std::vector<Elt> &C) : Value(json::Array(C)) {}
Value(json::Object &&Properties) : Type(T_Object) {
create<json::Object>(std::move(Properties));
}
template <typename Elt>
Value(const std::map<std::string, Elt> &C) : Value(json::Object(C)) {}
// Strings: types with value semantics. Must be valid UTF-8.
Value(std::string V) : Type(T_String) {
if (LLVM_UNLIKELY(!isUTF8(V))) {
assert(false && "Invalid UTF-8 in value used as JSON");
V = fixUTF8(std::move(V));
}
create<std::string>(std::move(V));
}
Value(const llvm::SmallVectorImpl<char> &V)
: Value(std::string(V.begin(), V.end())) {}
Value(const llvm::formatv_object_base &V) : Value(V.str()) {}
// Strings: types with reference semantics. Must be valid UTF-8.
Value(StringRef V) : Type(T_StringRef) {
create<llvm::StringRef>(V);
if (LLVM_UNLIKELY(!isUTF8(V))) {
assert(false && "Invalid UTF-8 in value used as JSON");
*this = Value(fixUTF8(V));
}
}
Value(const char *V) : Value(StringRef(V)) {}
Value(std::nullptr_t) : Type(T_Null) {}
// Boolean (disallow implicit conversions).
// (The last template parameter is a dummy to keep templates distinct.)
template <typename T, typename = std::enable_if_t<std::is_same_v<T, bool>>,
bool = false>
Value(T B) : Type(T_Boolean) {
create<bool>(B);
}
// Unsigned 64-bit integers.
template <typename T, typename = std::enable_if_t<is_uint_64_bit_v<T>>>
Value(T V) : Type(T_UINT64) {
create<uint64_t>(uint64_t{V});
}
// Integers (except boolean and uint64_t).
// Must be non-narrowing convertible to int64_t.
template <typename T, typename = std::enable_if_t<std::is_integral_v<T>>,
typename = std::enable_if_t<!std::is_same_v<T, bool>>,
typename = std::enable_if_t<!is_uint_64_bit_v<T>>>
Value(T I) : Type(T_Integer) {
create<int64_t>(int64_t{I});
}
// Floating point. Must be non-narrowing convertible to double.
template <typename T,
typename = std::enable_if_t<std::is_floating_point_v<T>>,
double * = nullptr>
Value(T D) : Type(T_Double) {
create<double>(double{D});
}
// Serializable types: with a toJSON(const T&)->Value function, found by ADL.
template <typename T,
typename = std::enable_if_t<
std::is_same_v<Value, decltype(toJSON(*(const T *)nullptr))>>,
Value * = nullptr>
Value(const T &V) : Value(toJSON(V)) {}
Value &operator=(const Value &M) {
destroy();
copyFrom(M);
return *this;
}
Value &operator=(Value &&M) {
destroy();
moveFrom(std::move(M));
return *this;
}
~Value() { destroy(); }
Kind kind() const {
switch (Type) {
case T_Null:
return Null;
case T_Boolean:
return Boolean;
case T_Double:
case T_Integer:
case T_UINT64:
return Number;
case T_String:
case T_StringRef:
return String;
case T_Object:
return Object;
case T_Array:
return Array;
}
llvm_unreachable("Unknown kind");
}
// Typed accessors return std::nullopt/nullptr if the Value is not of this
// type.
std::optional<std::nullptr_t> getAsNull() const {
if (LLVM_LIKELY(Type == T_Null))
return nullptr;
return std::nullopt;
}
std::optional<bool> getAsBoolean() const {
if (LLVM_LIKELY(Type == T_Boolean))
return as<bool>();
return std::nullopt;
}
std::optional<double> getAsNumber() const {
if (LLVM_LIKELY(Type == T_Double))
return as<double>();
if (LLVM_LIKELY(Type == T_Integer))
return as<int64_t>();
if (LLVM_LIKELY(Type == T_UINT64))
return as<uint64_t>();
return std::nullopt;
}
// Succeeds if the Value is a Number, and exactly representable as int64_t.
std::optional<int64_t> getAsInteger() const {
if (LLVM_LIKELY(Type == T_Integer))
return as<int64_t>();
if (LLVM_LIKELY(Type == T_UINT64)) {
uint64_t U = as<uint64_t>();
if (LLVM_LIKELY(U <= uint64_t(std::numeric_limits<int64_t>::max()))) {
return U;
}
}
if (LLVM_LIKELY(Type == T_Double)) {
double D = as<double>();
if (LLVM_LIKELY(std::modf(D, &D) == 0.0 &&
D >= double(std::numeric_limits<int64_t>::min()) &&
D <= double(std::numeric_limits<int64_t>::max())))
return D;
}
return std::nullopt;
}
std::optional<uint64_t> getAsUINT64() const {
if (Type == T_UINT64)
return as<uint64_t>();
else if (Type == T_Integer) {
int64_t N = as<int64_t>();
if (N >= 0)
return as<uint64_t>();
}
return std::nullopt;
}
std::optional<llvm::StringRef> getAsString() const {
if (Type == T_String)
return llvm::StringRef(as<std::string>());
if (LLVM_LIKELY(Type == T_StringRef))
return as<llvm::StringRef>();
return std::nullopt;
}
const json::Object *getAsObject() const {
return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
}
json::Object *getAsObject() {
return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
}
const json::Array *getAsArray() const {
return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
}
json::Array *getAsArray() {
return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
}
private:
void destroy();
void copyFrom(const Value &M);
// We allow moving from *const* Values, by marking all members as mutable!
// This hack is needed to support initializer-list syntax efficiently.
// (std::initializer_list<T> is a container of const T).
void moveFrom(const Value &&M);
friend class Array;
friend class Object;
template <typename T, typename... U> void create(U &&... V) {
#if LLVM_ADDRESS_SANITIZER_BUILD
// Unpoisoning to prevent overwriting poisoned object (e.g., annotated short
// string). Objects that have had their memory poisoned may cause an ASan
// error if their memory is reused without calling their destructor.
// Unpoisoning the memory prevents this error from occurring.
// FIXME: This is a temporary solution to prevent buildbots from failing.
// The more appropriate approach would be to call the object's destructor
// to unpoison memory. This would prevent any potential memory leaks (long
// strings). Read for details:
// https://github.com/llvm/llvm-project/pull/79065#discussion_r1462621761
__asan_unpoison_memory_region(&Union, sizeof(T));
#endif
new (reinterpret_cast<T *>(&Union)) T(std::forward<U>(V)...);
}
template <typename T> T &as() const {
// Using this two-step static_cast via void * instead of reinterpret_cast
// silences a -Wstrict-aliasing false positive from GCC6 and earlier.
void *Storage = static_cast<void *>(&Union);
return *static_cast<T *>(Storage);
}
friend class OStream;
enum ValueType : char16_t {
T_Null,
T_Boolean,
T_Double,
T_Integer,
T_UINT64,
T_StringRef,
T_String,
T_Object,
T_Array,
};
// All members mutable, see moveFrom().
mutable ValueType Type;
mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, uint64_t,
llvm::StringRef, std::string, json::Array,
json::Object>
Union;
friend bool operator==(const Value &, const Value &);
};
bool operator==(const Value &, const Value &);
inline bool operator!=(const Value &L, const Value &R) { return !(L == R); }
// Array Methods
inline Value &Array::operator[](size_t I) { return V[I]; }
inline const Value &Array::operator[](size_t I) const { return V[I]; }
inline Value &Array::front() { return V.front(); }
inline const Value &Array::front() const { return V.front(); }
inline Value &Array::back() { return V.back(); }
inline const Value &Array::back() const { return V.back(); }
inline Value *Array::data() { return V.data(); }
inline const Value *Array::data() const { return V.data(); }
inline typename Array::iterator Array::begin() { return V.begin(); }
inline typename Array::const_iterator Array::begin() const { return V.begin(); }
inline typename Array::iterator Array::end() { return V.end(); }
inline typename Array::const_iterator Array::end() const { return V.end(); }
inline bool Array::empty() const { return V.empty(); }
inline size_t Array::size() const { return V.size(); }
inline void Array::reserve(size_t S) { V.reserve(S); }
inline void Array::clear() { V.clear(); }
inline void Array::push_back(const Value &E) { V.push_back(E); }
inline void Array::push_back(Value &&E) { V.push_back(std::move(E)); }
template <typename... Args> inline void Array::emplace_back(Args &&...A) {
V.emplace_back(std::forward<Args>(A)...);
}
inline void Array::pop_back() { V.pop_back(); }
inline typename Array::iterator Array::insert(const_iterator P, const Value &E) {
return V.insert(P, E);
}
inline typename Array::iterator Array::insert(const_iterator P, Value &&E) {
return V.insert(P, std::move(E));
}
template <typename It>
inline typename Array::iterator Array::insert(const_iterator P, It A, It Z) {
return V.insert(P, A, Z);
}
template <typename... Args>
inline typename Array::iterator Array::emplace(const_iterator P, Args &&...A) {
return V.emplace(P, std::forward<Args>(A)...);
}
inline bool operator==(const Array &L, const Array &R) { return L.V == R.V; }
/// ObjectKey is a used to capture keys in Object. Like Value but:
/// - only strings are allowed
/// - it's optimized for the string literal case (Owned == nullptr)
/// Like Value, strings must be UTF-8. See isUTF8 documentation for details.
class ObjectKey {
public:
ObjectKey(const char *S) : ObjectKey(StringRef(S)) {}
ObjectKey(std::string S) : Owned(new std::string(std::move(S))) {
if (LLVM_UNLIKELY(!isUTF8(*Owned))) {
assert(false && "Invalid UTF-8 in value used as JSON");
*Owned = fixUTF8(std::move(*Owned));
}
Data = *Owned;
}
ObjectKey(llvm::StringRef S) : Data(S) {
if (LLVM_UNLIKELY(!isUTF8(Data))) {
assert(false && "Invalid UTF-8 in value used as JSON");
*this = ObjectKey(fixUTF8(S));
}
}
ObjectKey(const llvm::SmallVectorImpl<char> &V)
: ObjectKey(std::string(V.begin(), V.end())) {}
ObjectKey(const llvm::formatv_object_base &V) : ObjectKey(V.str()) {}
ObjectKey(const ObjectKey &C) { *this = C; }
ObjectKey(ObjectKey &&C) : ObjectKey(static_cast<const ObjectKey &&>(C)) {}
ObjectKey &operator=(const ObjectKey &C) {
if (C.Owned) {
Owned.reset(new std::string(*C.Owned));
Data = *Owned;
} else {
Data = C.Data;
}
return *this;
}
ObjectKey &operator=(ObjectKey &&) = default;
operator llvm::StringRef() const { return Data; }
std::string str() const { return Data.str(); }
private:
// FIXME: this is unneccesarily large (3 pointers). Pointer + length + owned
// could be 2 pointers at most.
std::unique_ptr<std::string> Owned;
llvm::StringRef Data;
};
inline bool operator==(const ObjectKey &L, const ObjectKey &R) {
return llvm::StringRef(L) == llvm::StringRef(R);
}
inline bool operator!=(const ObjectKey &L, const ObjectKey &R) {
return !(L == R);
}
inline bool operator<(const ObjectKey &L, const ObjectKey &R) {
return StringRef(L) < StringRef(R);
}
struct Object::KV {
ObjectKey K;
Value V;
};
inline Object::Object(std::initializer_list<KV> Properties) {
for (const auto &P : Properties) {
auto R = try_emplace(P.K, nullptr);
if (R.second)
R.first->getSecond().moveFrom(std::move(P.V));
}
}
inline std::pair<Object::iterator, bool> Object::insert(KV E) {
return try_emplace(std::move(E.K), std::move(E.V));
}
inline bool Object::erase(StringRef K) {
return M.erase(ObjectKey(K));
}
std::vector<const Object::value_type *> sortedElements(const Object &O);
/// A "cursor" marking a position within a Value.
/// The Value is a tree, and this is the path from the root to the current node.
/// This is used to associate errors with particular subobjects.
class Path {
public:
class Root;
/// Records that the value at the current path is invalid.
/// Message is e.g. "expected number" and becomes part of the final error.
/// This overwrites any previously written error message in the root.
void report(llvm::StringLiteral Message);
/// The root may be treated as a Path.
Path(Root &R) : Parent(nullptr), Seg(&R) {}
/// Derives a path for an array element: this[Index]
Path index(unsigned Index) const { return Path(this, Segment(Index)); }
/// Derives a path for an object field: this.Field
Path field(StringRef Field) const { return Path(this, Segment(Field)); }
private:
/// One element in a JSON path: an object field (.foo) or array index [27].
/// Exception: the root Path encodes a pointer to the Path::Root.
class Segment {
uintptr_t Pointer;
unsigned Offset;
public:
Segment() = default;
Segment(Root *R) : Pointer(reinterpret_cast<uintptr_t>(R)) {}
Segment(llvm::StringRef Field)
: Pointer(reinterpret_cast<uintptr_t>(Field.data())),
Offset(static_cast<unsigned>(Field.size())) {}
Segment(unsigned Index) : Pointer(0), Offset(Index) {}
bool isField() const { return Pointer != 0; }
StringRef field() const {
return StringRef(reinterpret_cast<const char *>(Pointer), Offset);
}
unsigned index() const { return Offset; }
Root *root() const { return reinterpret_cast<Root *>(Pointer); }
};
const Path *Parent;
Segment Seg;
Path(const Path *Parent, Segment S) : Parent(Parent), Seg(S) {}
};
/// The root is the trivial Path to the root value.
/// It also stores the latest reported error and the path where it occurred.
class Path::Root {
llvm::StringRef Name;
llvm::StringLiteral ErrorMessage;
std::vector<Path::Segment> ErrorPath; // Only valid in error state. Reversed.
friend void Path::report(llvm::StringLiteral Message);
public:
Root(llvm::StringRef Name = "") : Name(Name), ErrorMessage("") {}
// No copy/move allowed as there are incoming pointers.
Root(Root &&) = delete;
Root &operator=(Root &&) = delete;
Root(const Root &) = delete;
Root &operator=(const Root &) = delete;
/// Returns the last error reported, or else a generic error.
Error getError() const;
/// Print the root value with the error shown inline as a comment.
/// Unrelated parts of the value are elided for brevity, e.g.
/// {
/// "id": 42,
/// "name": /* expected string */ null,
/// "properties": { ... }
/// }
void printErrorContext(const Value &, llvm::raw_ostream &) const;
};
// Standard deserializers are provided for primitive types.
// See comments on Value.
inline bool fromJSON(const Value &E, std::string &Out, Path P) {
if (auto S = E.getAsString()) {
Out = std::string(*S);
return true;
}
P.report("expected string");
return false;
}
inline bool fromJSON(const Value &E, int &Out, Path P) {
if (auto S = E.getAsInteger()) {
Out = *S;
return true;
}
P.report("expected integer");
return false;
}
inline bool fromJSON(const Value &E, int64_t &Out, Path P) {
if (auto S = E.getAsInteger()) {
Out = *S;
return true;
}
P.report("expected integer");
return false;
}
inline bool fromJSON(const Value &E, double &Out, Path P) {
if (auto S = E.getAsNumber()) {
Out = *S;
return true;
}
P.report("expected number");
return false;
}
inline bool fromJSON(const Value &E, bool &Out, Path P) {
if (auto S = E.getAsBoolean()) {
Out = *S;
return true;
}
P.report("expected boolean");
return false;
}
inline bool fromJSON(const Value &E, uint64_t &Out, Path P) {
if (auto S = E.getAsUINT64()) {
Out = *S;
return true;
}
P.report("expected uint64_t");
return false;
}
inline bool fromJSON(const Value &E, std::nullptr_t &Out, Path P) {
if (auto S = E.getAsNull()) {
Out = *S;
return true;
}
P.report("expected null");
return false;
}
template <typename T>
bool fromJSON(const Value &E, std::optional<T> &Out, Path P) {
if (E.getAsNull()) {
Out = std::nullopt;
return true;
}
T Result = {};
if (!fromJSON(E, Result, P))
return false;
Out = std::move(Result);
return true;
}
template <typename T>
bool fromJSON(const Value &E, std::vector<T> &Out, Path P) {
if (auto *A = E.getAsArray()) {
Out.clear();
Out.resize(A->size());
for (size_t I = 0; I < A->size(); ++I)
if (!fromJSON((*A)[I], Out[I], P.index(I)))
return false;
return true;
}
P.report("expected array");
return false;
}
template <typename T>
bool fromJSON(const Value &E, std::map<std::string, T> &Out, Path P) {
if (auto *O = E.getAsObject()) {
Out.clear();
for (const auto &KV : *O)
if (!fromJSON(KV.second, Out[std::string(llvm::StringRef(KV.first))],
P.field(KV.first)))
return false;
return true;
}
P.report("expected object");
return false;
}
// Allow serialization of std::optional<T> for supported T.
template <typename T> Value toJSON(const std::optional<T> &Opt) {
return Opt ? Value(*Opt) : Value(nullptr);
}
/// Helper for mapping JSON objects onto protocol structs.
///
/// Example:
/// \code
/// bool fromJSON(const Value &E, MyStruct &R, Path P) {
/// ObjectMapper O(E, P);
/// // When returning false, error details were already reported.
/// return O && O.map("mandatory_field", R.MandatoryField) &&
/// O.mapOptional("optional_field", R.OptionalField);
/// }
/// \endcode
class ObjectMapper {
public:
/// If O is not an object, this mapper is invalid and an error is reported.
ObjectMapper(const Value &E, Path P) : O(E.getAsObject()), P(P) {
if (!O)
P.report("expected object");
}
/// True if the expression is an object.
/// Must be checked before calling map().
operator bool() const { return O; }
/// Maps a property to a field.
/// If the property is missing or invalid, reports an error.
template <typename T> bool map(StringLiteral Prop, T &Out) {
assert(*this && "Must check this is an object before calling map()");
if (const Value *E = O->get(Prop))
return fromJSON(*E, Out, P.field(Prop));
P.field(Prop).report("missing value");
return false;
}
/// Maps a property to a field, if it exists.
/// If the property exists and is invalid, reports an error.
/// (Optional requires special handling, because missing keys are OK).
template <typename T> bool map(StringLiteral Prop, std::optional<T> &Out) {
assert(*this && "Must check this is an object before calling map()");
if (const Value *E = O->get(Prop))
return fromJSON(*E, Out, P.field(Prop));
Out = std::nullopt;
return true;
}
/// Maps a property to a field, if it exists.
/// If the property exists and is invalid, reports an error.
/// If the property does not exist, Out is unchanged.
template <typename T> bool mapOptional(StringLiteral Prop, T &Out) {
assert(*this && "Must check this is an object before calling map()");
if (const Value *E = O->get(Prop))
return fromJSON(*E, Out, P.field(Prop));
return true;
}
private:
const Object *O;
Path P;
};
/// Parses the provided JSON source, or returns a ParseError.
/// The returned Value is self-contained and owns its strings (they do not refer
/// to the original source).
llvm::Expected<Value> parse(llvm::StringRef JSON);
class ParseError : public llvm::ErrorInfo<ParseError> {
const char *Msg;
unsigned Line, Column, Offset;
public:
static char ID;
ParseError(const char *Msg, unsigned Line, unsigned Column, unsigned Offset)
: Msg(Msg), Line(Line), Column(Column), Offset(Offset) {}
void log(llvm::raw_ostream &OS) const override {
OS << llvm::formatv("[{0}:{1}, byte={2}]: {3}", Line, Column, Offset, Msg);
}
std::error_code convertToErrorCode() const override {
return llvm::inconvertibleErrorCode();
}
};
/// Version of parse() that converts the parsed value to the type T.
/// RootName describes the root object and is used in error messages.
template <typename T>
Expected<T> parse(const llvm::StringRef &JSON, const char *RootName = "") {
auto V = parse(JSON);
if (!V)
return V.takeError();
Path::Root R(RootName);
T Result;
if (fromJSON(*V, Result, R))
return std::move(Result);
return R.getError();
}
/// json::OStream allows writing well-formed JSON without materializing
/// all structures as json::Value ahead of time.
/// It's faster, lower-level, and less safe than OS << json::Value.
/// It also allows emitting more constructs, such as comments.
///
/// Only one "top-level" object can be written to a stream.
/// Simplest usage involves passing lambdas (Blocks) to fill in containers:
///
/// json::OStream J(OS);
/// J.array([&]{
/// for (const Event &E : Events)
/// J.object([&] {
/// J.attribute("timestamp", int64_t(E.Time));
/// J.attributeArray("participants", [&] {
/// for (const Participant &P : E.Participants)
/// J.value(P.toString());
/// });
/// });
/// });
///
/// This would produce JSON like:
///
/// [
/// {
/// "timestamp": 19287398741,
/// "participants": [
/// "King Kong",
/// "Miley Cyrus",
/// "Cleopatra"
/// ]
/// },
/// ...
/// ]
///
/// The lower level begin/end methods (arrayBegin()) are more flexible but
/// care must be taken to pair them correctly:
///
/// json::OStream J(OS);
// J.arrayBegin();
/// for (const Event &E : Events) {
/// J.objectBegin();
/// J.attribute("timestamp", int64_t(E.Time));
/// J.attributeBegin("participants");
/// for (const Participant &P : E.Participants)
/// J.value(P.toString());
/// J.attributeEnd();
/// J.objectEnd();
/// }
/// J.arrayEnd();
///
/// If the call sequence isn't valid JSON, asserts will fire in debug mode.
/// This can be mismatched begin()/end() pairs, trying to emit attributes inside
/// an array, and so on.
/// With asserts disabled, this is undefined behavior.
class OStream {
public:
using Block = llvm::function_ref<void()>;
// If IndentSize is nonzero, output is pretty-printed.
explicit OStream(llvm::raw_ostream &OS, unsigned IndentSize = 0)
: OS(OS), IndentSize(IndentSize) {
Stack.emplace_back();
}
~OStream() {
assert(Stack.size() == 1 && "Unmatched begin()/end()");
assert(Stack.back().Ctx == Singleton);
assert(Stack.back().HasValue && "Did not write top-level value");
}
/// Flushes the underlying ostream. OStream does not buffer internally.
void flush() { OS.flush(); }
// High level functions to output a value.
// Valid at top-level (exactly once), in an attribute value (exactly once),
// or in an array (any number of times).
/// Emit a self-contained value (number, string, vector<string> etc).
void value(const Value &V);
/// Emit an array whose elements are emitted in the provided Block.
void array(Block Contents) {
arrayBegin();
Contents();
arrayEnd();
}
/// Emit an object whose elements are emitted in the provided Block.
void object(Block Contents) {
objectBegin();
Contents();
objectEnd();
}
/// Emit an externally-serialized value.
/// The caller must write exactly one valid JSON value to the provided stream.
/// No validation or formatting of this value occurs.
void rawValue(llvm::function_ref<void(raw_ostream &)> Contents) {
rawValueBegin();
Contents(OS);
rawValueEnd();
}
void rawValue(llvm::StringRef Contents) {
rawValue([&](raw_ostream &OS) { OS << Contents; });
}
/// Emit a JavaScript comment associated with the next printed value.
/// The string must be valid until the next attribute or value is emitted.
/// Comments are not part of standard JSON, and many parsers reject them!
void comment(llvm::StringRef);
// High level functions to output object attributes.
// Valid only within an object (any number of times).
/// Emit an attribute whose value is self-contained (number, vector<int> etc).
void attribute(llvm::StringRef Key, const Value& Contents) {
attributeImpl(Key, [&] { value(Contents); });
}
/// Emit an attribute whose value is an array with elements from the Block.
void attributeArray(llvm::StringRef Key, Block Contents) {
attributeImpl(Key, [&] { array(Contents); });
}
/// Emit an attribute whose value is an object with attributes from the Block.
void attributeObject(llvm::StringRef Key, Block Contents) {
attributeImpl(Key, [&] { object(Contents); });
}
// Low-level begin/end functions to output arrays, objects, and attributes.
// Must be correctly paired. Allowed contexts are as above.
void arrayBegin();
void arrayEnd();
void objectBegin();
void objectEnd();
void attributeBegin(llvm::StringRef Key);
void attributeEnd();
raw_ostream &rawValueBegin();
void rawValueEnd();
private:
void attributeImpl(llvm::StringRef Key, Block Contents) {
attributeBegin(Key);
Contents();
attributeEnd();
}
void valueBegin();
void flushComment();
void newline();
enum Context {
Singleton, // Top level, or object attribute.
Array,
Object,
RawValue, // External code writing a value to OS directly.
};
struct State {
Context Ctx = Singleton;
bool HasValue = false;
};
llvm::SmallVector<State, 16> Stack; // Never empty.
llvm::StringRef PendingComment;
llvm::raw_ostream &OS;
unsigned IndentSize;
unsigned Indent = 0;
};
/// Serializes this Value to JSON, writing it to the provided stream.
/// The formatting is compact (no extra whitespace) and deterministic.
/// For pretty-printing, use the formatv() format_provider below.
inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Value &V) {
OStream(OS).value(V);
return OS;
}
} // namespace json
/// Allow printing json::Value with formatv().
/// The default style is basic/compact formatting, like operator<<.
/// A format string like formatv("{0:2}", Value) pretty-prints with indent 2.
template <> struct format_provider<llvm::json::Value> {
static void format(const llvm::json::Value &, raw_ostream &, StringRef);
};
} // namespace llvm
#endif
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