Files
clang-p2996/lldb/source/Utility/StructuredData.cpp
Sam McCall fa69b60806 [JSON] Add error reporting to fromJSON and ObjectMapper
Translating between JSON objects and C++ strutctures is common.
From experience in clangd, fromJSON/ObjectMapper work well and save a lot of
code, but aren't adopted elsewhere at least partly due to total lack of error
reporting beyond "ok"/"bad".

The recently-added error model should be rich enough for most applications.
It requires tracking the path within the root object and reporting local
errors at appropriate places.
To do this, we exploit the fact that the call graph of recursive
parse functions mirror the structure of the JSON itself.
The current path is represented as a linked list of segments, each of which is
on the stack as a parameter. Concretely, fromJSON now looks like:
  bool fromJSON(const Value&, T&, Path);

Beyond the signature change, this is reasonably unobtrusive: building
the path segments is mostly handled by ObjectMapper and the vector<T> fromJSON.
However the root caller of fromJSON must now create a Root object to
store the errors, which is a little clunky.

I've added high-level parse<T>(StringRef) -> Expected<T>, but it's not
general enough to be the primary interface I think (at least, not usable in
clangd).

All existing users (mostly just clangd) are updated in this patch,
making this change backwards-compatible is a bit hairy.

Differential Revision: https://reviews.llvm.org/D88103
2020-09-24 01:20:09 +02:00

175 lines
5.3 KiB
C++

//===-- StructuredData.cpp ------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "lldb/Utility/StructuredData.h"
#include "lldb/Utility/FileSpec.h"
#include "lldb/Utility/Status.h"
#include "llvm/Support/MemoryBuffer.h"
#include <cerrno>
#include <cstdlib>
#include <inttypes.h>
using namespace lldb_private;
using namespace llvm;
static StructuredData::ObjectSP ParseJSONValue(json::Value &value);
static StructuredData::ObjectSP ParseJSONObject(json::Object *object);
static StructuredData::ObjectSP ParseJSONArray(json::Array *array);
StructuredData::ObjectSP
StructuredData::ParseJSON(const std::string &json_text) {
llvm::Expected<json::Value> value = json::parse(json_text);
if (!value) {
llvm::consumeError(value.takeError());
return nullptr;
}
return ParseJSONValue(*value);
}
StructuredData::ObjectSP
StructuredData::ParseJSONFromFile(const FileSpec &input_spec, Status &error) {
StructuredData::ObjectSP return_sp;
auto buffer_or_error = llvm::MemoryBuffer::getFile(input_spec.GetPath());
if (!buffer_or_error) {
error.SetErrorStringWithFormatv("could not open input file: {0} - {1}.",
input_spec.GetPath(),
buffer_or_error.getError().message());
return return_sp;
}
llvm::Expected<json::Value> value =
json::parse(buffer_or_error.get()->getBuffer().str());
if (value)
return ParseJSONValue(*value);
error.SetErrorString(toString(value.takeError()));
return StructuredData::ObjectSP();
}
static StructuredData::ObjectSP ParseJSONValue(json::Value &value) {
if (json::Object *O = value.getAsObject())
return ParseJSONObject(O);
if (json::Array *A = value.getAsArray())
return ParseJSONArray(A);
if (auto s = value.getAsString())
return std::make_shared<StructuredData::String>(*s);
if (auto b = value.getAsBoolean())
return std::make_shared<StructuredData::Boolean>(*b);
if (auto i = value.getAsInteger(i))
return std::make_shared<StructuredData::Integer>(*i);
if (auto d = value.getAsNumber())
return std::make_shared<StructuredData::Float>(*d);
return StructuredData::ObjectSP();
}
static StructuredData::ObjectSP ParseJSONObject(json::Object *object) {
auto dict_up = std::make_unique<StructuredData::Dictionary>();
for (auto &KV : *object) {
StringRef key = KV.first;
json::Value value = KV.second;
if (StructuredData::ObjectSP value_sp = ParseJSONValue(value))
dict_up->AddItem(key, value_sp);
}
return std::move(dict_up);
}
static StructuredData::ObjectSP ParseJSONArray(json::Array *array) {
auto array_up = std::make_unique<StructuredData::Array>();
for (json::Value &value : *array) {
if (StructuredData::ObjectSP value_sp = ParseJSONValue(value))
array_up->AddItem(value_sp);
}
return std::move(array_up);
}
StructuredData::ObjectSP
StructuredData::Object::GetObjectForDotSeparatedPath(llvm::StringRef path) {
if (this->GetType() == lldb::eStructuredDataTypeDictionary) {
std::pair<llvm::StringRef, llvm::StringRef> match = path.split('.');
std::string key = match.first.str();
ObjectSP value = this->GetAsDictionary()->GetValueForKey(key);
if (value.get()) {
// Do we have additional words to descend? If not, return the value
// we're at right now.
if (match.second.empty()) {
return value;
} else {
return value->GetObjectForDotSeparatedPath(match.second);
}
}
return ObjectSP();
}
if (this->GetType() == lldb::eStructuredDataTypeArray) {
std::pair<llvm::StringRef, llvm::StringRef> match = path.split('[');
if (match.second.empty()) {
return this->shared_from_this();
}
errno = 0;
uint64_t val = strtoul(match.second.str().c_str(), nullptr, 10);
if (errno == 0) {
return this->GetAsArray()->GetItemAtIndex(val);
}
return ObjectSP();
}
return this->shared_from_this();
}
void StructuredData::Object::DumpToStdout(bool pretty_print) const {
json::OStream stream(llvm::outs(), pretty_print ? 2 : 0);
Serialize(stream);
}
void StructuredData::Array::Serialize(json::OStream &s) const {
s.arrayBegin();
for (const auto &item_sp : m_items) {
item_sp->Serialize(s);
}
s.arrayEnd();
}
void StructuredData::Integer::Serialize(json::OStream &s) const {
s.value(static_cast<int64_t>(m_value));
}
void StructuredData::Float::Serialize(json::OStream &s) const {
s.value(m_value);
}
void StructuredData::Boolean::Serialize(json::OStream &s) const {
s.value(m_value);
}
void StructuredData::String::Serialize(json::OStream &s) const {
s.value(m_value);
}
void StructuredData::Dictionary::Serialize(json::OStream &s) const {
s.objectBegin();
for (const auto &pair : m_dict) {
s.attributeBegin(pair.first.GetStringRef());
pair.second->Serialize(s);
s.attributeEnd();
}
s.objectEnd();
}
void StructuredData::Null::Serialize(json::OStream &s) const {
s.value(nullptr);
}
void StructuredData::Generic::Serialize(json::OStream &s) const {
s.value(llvm::formatv("{0:X}", m_object));
}