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//===--- ConfigProvider.h - Loading of user configuration --------*- C++-*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Various clangd features have configurable behaviour (or can be disabled).
// The configuration system allows users to control this:
// - in a user config file, a project config file, via LSP, or via flags
// - specifying different settings for different files
// This file defines the structures used for this, that produce a Config.
#include "llvm/ADT/FunctionExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/SMLoc.h"
#include "llvm/Support/SourceMgr.h"
#include <chrono>
#include <string>
#include <vector>
namespace clang {
namespace clangd {
struct Config;
class ThreadsafeFS;
namespace config {
/// Describes the context used to evaluate configuration fragments.
struct Params {
/// Absolute path to a source file we're applying the config to. Unix slashes.
/// Empty if not configuring a particular file.
llvm::StringRef Path;
/// Hint that stale data is OK to improve performance (e.g. avoid IO).
/// FreshTime sets a bound for how old the data can be.
/// By default, providers should validate caches against the data source.
std::chrono::steady_clock::time_point FreshTime =
/// Used to report problems in parsing or interpreting a config.
/// Errors reflect structurally invalid config that should be user-visible.
/// Warnings reflect e.g. unknown properties that are recoverable.
/// Notes are used to report files and fragments.
/// (This can be used to track when previous warnings/errors have been "fixed").
using DiagnosticCallback = llvm::function_ref<void(const llvm::SMDiagnostic &)>;
/// A chunk of configuration that has been fully analyzed and is ready to apply.
/// Typically this is obtained from a Fragment by calling Fragment::compile().
/// Calling it updates the configuration to reflect settings from the fragment.
/// Returns true if the condition was met and the settings were used.
using CompiledFragment = std::function<bool(const Params &, Config &)>;
/// A source of configuration fragments.
/// Generally these providers reflect a fixed policy for obtaining config,
/// but return different concrete configuration over time.
/// e.g. a provider that reads config from files is responsive to file changes.
class Provider {
virtual ~Provider() = default;
/// Reads fragments from a single YAML file with a fixed path. If non-empty,
/// Directory will be used to resolve relative paths in the fragments.
static std::unique_ptr<Provider> fromYAMLFile(llvm::StringRef AbsPath,
llvm::StringRef Directory,
const ThreadsafeFS &,
bool Trusted = false);
// Reads fragments from YAML files found relative to ancestors of Params.Path.
// All fragments that exist are returned, starting from distant ancestors.
// For instance, given RelPath of ".clangd", then for source file /foo/,
// the searched fragments are [/.clangd, /foo/.clangd].
// If Params does not specify a path, no fragments are returned.
static std::unique_ptr<Provider>
fromAncestorRelativeYAMLFiles(llvm::StringRef RelPath, const ThreadsafeFS &,
bool Trusted = false);
/// A provider that includes fragments from all the supplied providers.
/// Order is preserved; later providers take precedence over earlier ones.
static std::unique_ptr<Provider> combine(std::vector<const Provider *>);
/// Build a config based on this provider.
Config getConfig(const Params &, DiagnosticCallback) const;
/// Provide fragments that may be relevant to the file.
/// The configuration provider is not responsible for testing conditions.
/// Providers are expected to cache compiled fragments, and only
/// reparse/recompile when the source data has changed.
/// Despite the need for caching, this function must be threadsafe.
/// When parsing/compiling, the DiagnosticCallback is used to report errors.
virtual std::vector<CompiledFragment>
getFragments(const Params &, DiagnosticCallback) const = 0;
} // namespace config
} // namespace clangd
} // namespace clang