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//===--- CodeComplete.h ------------------------------------------*- 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
// Code completion provides suggestions for what the user might type next.
// After "std::string S; S." we might suggest members of std::string.
// Signature help describes the parameters of a function as you type them.
#include "ASTSignals.h"
#include "Compiler.h"
#include "Headers.h"
#include "Protocol.h"
#include "Quality.h"
#include "index/Index.h"
#include "index/Symbol.h"
#include "index/SymbolOrigin.h"
#include "support/Logger.h"
#include "support/Markup.h"
#include "support/Path.h"
#include "clang/Sema/CodeCompleteConsumer.h"
#include "clang/Sema/CodeCompleteOptions.h"
#include "clang/Tooling/CompilationDatabase.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Error.h"
#include <functional>
#include <future>
namespace clang {
class NamedDecl;
namespace clangd {
struct PreambleData;
struct CodeCompletion;
struct CodeCompleteOptions {
/// Returns options that can be passed to clang's completion engine.
clang::CodeCompleteOptions getClangCompleteOpts() const;
/// When true, completion items will contain expandable code snippets in
/// completion (e.g. `return ${1:expression}` or `foo(${1:int a}, ${2:int
/// b})).
bool EnableSnippets = false;
/// Include results that are not legal completions in the current context.
/// For example, private members are usually inaccessible.
bool IncludeIneligibleResults = false;
/// Combine overloads into a single completion item where possible.
/// If none, the implementation may choose an appropriate behavior.
/// (In practice, ClangdLSPServer enables bundling if the client claims
/// to supports signature help).
llvm::Optional<bool> BundleOverloads;
/// Limit the number of results returned (0 means no limit).
/// If more results are available, we set CompletionList.isIncomplete.
size_t Limit = 0;
/// Whether to present doc comments as plain-text or markdown.
MarkupKind DocumentationFormat = MarkupKind::PlainText;
enum IncludeInsertion {
} InsertIncludes = IncludeInsertion::IWYU;
/// A visual indicator to prepend to the completion label to indicate whether
/// completion result would trigger an #include insertion or not.
struct IncludeInsertionIndicator {
std::string Insert = "•";
std::string NoInsert = " ";
} IncludeIndicator;
/// Expose origins of completion items in the label (for debugging).
bool ShowOrigins = false;
// Populated internally by clangd, do not set.
/// If `Index` is set, it is used to augment the code completion
/// results.
/// FIXME(ioeric): we might want a better way to pass the index around inside
/// clangd.
const SymbolIndex *Index = nullptr;
const ASTSignals *MainFileSignals = nullptr;
/// Include completions that require small corrections, e.g. change '.' to
/// '->' on member access etc.
bool IncludeFixIts = false;
/// Whether to generate snippets for function arguments on code-completion.
/// Needs snippets to be enabled as well.
bool EnableFunctionArgSnippets = true;
/// Whether to include index symbols that are not defined in the scopes
/// visible from the code completion point. This applies in contexts without
/// explicit scope qualifiers.
/// Such completions can insert scope qualifiers.
bool AllScopes = false;
/// Whether to use the clang parser, or fallback to text-based completion
/// (using identifiers in the current file and symbol indexes).
enum CodeCompletionParse {
/// Block until we can run the parser (e.g. preamble is built).
/// Return an error if this fails.
/// Run the parser if inputs (preamble) are ready.
/// Otherwise, use text-based completion.
/// Always use text-based completion.
} RunParser = ParseIfReady;
/// Callback invoked on all CompletionCandidate after they are scored and
/// before they are ranked (by -Score). Thus the results are yielded in
/// arbitrary order.
/// This callbacks allows capturing various internal structures used by clangd
/// during code completion. Eg: Symbol quality and relevance signals.
std::function<void(const CodeCompletion &, const SymbolQualitySignals &,
const SymbolRelevanceSignals &, float Score)>
/// Model to use for ranking code completion candidates.
enum CodeCompletionRankingModel {
} RankingModel = DecisionForest;
/// Callback used to score a CompletionCandidate if DecisionForest ranking
/// model is enabled.
/// This allows us to inject experimental models and compare them with
/// baseline model using A/B testing.
const SymbolQualitySignals &, const SymbolRelevanceSignals &, float Base)>
DecisionForestScorer = &evaluateDecisionForest;
/// Weight for combining NameMatch and Prediction of DecisionForest.
/// CompletionScore is NameMatch * pow(Base, Prediction).
/// The optimal value of Base largely depends on the semantics of the model
/// and prediction score (e.g. algorithm used during training, number of
/// trees, etc.). Usually if the range of Prediciton is [-20, 20] then a Base
/// in [1.2, 1.7] works fine.
/// Semantics: E.g. For Base = 1.3, if the Prediciton score reduces by 2.6
/// points then completion score reduces by 50% or 1.3^(-2.6).
float DecisionForestBase = 1.3f;
// Semi-structured representation of a code-complete suggestion for our C++ API.
// We don't use the LSP structures here (unlike most features) as we want
// to expose more data to allow for more precise testing and evaluation.
struct CodeCompletion {
// The unqualified name of the symbol or other completion item.
std::string Name;
// The scope qualifier for the symbol name. e.g. "ns1::ns2::"
// Empty for non-symbol completions. Not inserted, but may be displayed.
std::string Scope;
// Text that must be inserted before the name, and displayed (e.g. base::).
std::string RequiredQualifier;
// Details to be displayed following the name. Not inserted.
std::string Signature;
// Text to be inserted following the name, in snippet format.
std::string SnippetSuffix;
// Type to be displayed for this completion.
std::string ReturnType;
// The parsed documentation comment.
llvm::Optional<markup::Document> Documentation;
CompletionItemKind Kind = CompletionItemKind::Missing;
// This completion item may represent several symbols that can be inserted in
// the same way, such as function overloads. In this case BundleSize > 1, and
// the following fields are summaries:
// - Signature is e.g. "(...)" for functions.
// - SnippetSuffix is similarly e.g. "(${0})".
// - ReturnType may be empty
// - Documentation may be from one symbol, or a combination of several
// Other fields should apply equally to all bundled completions.
unsigned BundleSize = 1;
SymbolOrigin Origin = SymbolOrigin::Unknown;
struct IncludeCandidate {
// The header through which this symbol could be included.
// Quoted string as expected by an #include directive, e.g. "<memory>".
// Empty for non-symbol completions, or when not known.
std::string Header;
// Present if Header should be inserted to use this item.
llvm::Optional<TextEdit> Insertion;
// All possible include headers ranked by preference. By default, the first
// include is used.
// If we've bundled together overloads that have different sets of includes,
// thse includes may not be accurate for all of them.
llvm::SmallVector<IncludeCandidate, 1> Includes;
/// Holds information about small corrections that needs to be done. Like
/// converting '->' to '.' on member access.
std::vector<TextEdit> FixIts;
/// Holds the range of the token we are going to replace with this completion.
Range CompletionTokenRange;
// Scores are used to rank completion items.
struct Scores {
// The score that items are ranked by.
float Total = 0.f;
// The finalScore with the fuzzy name match score excluded.
// When filtering client-side, editors should calculate the new fuzzy score,
// whose scale is 0-1 (with 1 = prefix match, special case 2 = exact match),
// and recompute finalScore = fuzzyScore * symbolScore.
float ExcludingName = 0.f;
// Component scores that contributed to the final score:
// Quality describes how important we think this candidate is,
// independent of the query.
// e.g. symbols with lots of incoming references have higher quality.
float Quality = 0.f;
// Relevance describes how well this candidate matched the query.
// e.g. symbols from nearby files have higher relevance.
float Relevance = 0.f;
Scores Score;
/// Indicates if this item is deprecated.
bool Deprecated = false;
// Serialize this to an LSP completion item. This is a lossy operation.
CompletionItem render(const CodeCompleteOptions &) const;
raw_ostream &operator<<(raw_ostream &, const CodeCompletion &);
struct CodeCompleteResult {
std::vector<CodeCompletion> Completions;
bool HasMore = false;
CodeCompletionContext::Kind Context = CodeCompletionContext::CCC_Other;
// The text that is being directly completed.
// Example: foo.pb^ -> foo.push_back()
// ~~
// Typically matches the textEdit.range of Completions, but not guaranteed to.
llvm::Optional<Range> CompletionRange;
// Usually the source will be parsed with a real C++ parser.
// But heuristics may be used instead if e.g. the preamble is not ready.
bool RanParser = true;
raw_ostream &operator<<(raw_ostream &, const CodeCompleteResult &);
/// A speculative and asynchronous fuzzy find index request (based on cached
/// request) that can be sent before parsing sema. This would reduce completion
/// latency if the speculation succeeds.
struct SpeculativeFuzzyFind {
/// A cached request from past code completions.
/// Set by caller of `codeComplete()`.
llvm::Optional<FuzzyFindRequest> CachedReq;
/// The actual request used by `codeComplete()`.
/// Set by `codeComplete()`. This can be used by callers to update cache.
llvm::Optional<FuzzyFindRequest> NewReq;
/// The result is consumed by `codeComplete()` if speculation succeeded.
/// NOTE: the destructor will wait for the async call to finish.
std::future<SymbolSlab> Result;
/// Gets code completions at a specified \p Pos in \p FileName.
/// If \p Preamble is nullptr, this runs code completion without compiling the
/// code.
/// If \p SpecFuzzyFind is set, a speculative and asynchronous fuzzy find index
/// request (based on cached request) will be run before parsing sema. In case
/// the speculative result is used by code completion (e.g. speculation failed),
/// the speculative result is not consumed, and `SpecFuzzyFind` is only
/// destroyed when the async request finishes.
CodeCompleteResult codeComplete(PathRef FileName, Position Pos,
const PreambleData *Preamble,
const ParseInputs &ParseInput,
CodeCompleteOptions Opts,
SpeculativeFuzzyFind *SpecFuzzyFind = nullptr);
/// Get signature help at a specified \p Pos in \p FileName.
SignatureHelp signatureHelp(PathRef FileName, Position Pos,
const PreambleData &Preamble,
const ParseInputs &ParseInput);
// For index-based completion, we only consider:
// * symbols in namespaces or translation unit scopes (e.g. no class
// members, no locals)
// * enum constants in unscoped enum decl (e.g. "red" in "enum {red};")
// * primary templates (no specializations)
// For the other cases, we let Clang do the completion because it does not
// need any non-local information and it will be much better at following
// lookup rules. Other symbols still appear in the index for other purposes,
// like workspace/symbols or textDocument/definition, but are not used for code
// completion.
bool isIndexedForCodeCompletion(const NamedDecl &ND, ASTContext &ASTCtx);
// Text immediately before the completion point that should be completed.
// This is heuristically derived from the source code, and is used when:
// - semantic analysis fails
// - semantic analysis may be slow, and we speculatively query the index
struct CompletionPrefix {
// The unqualified partial name.
// If there is none, begin() == end() == completion position.
llvm::StringRef Name;
// The spelled scope qualifier, such as Foo::.
// If there is none, begin() == end() == Name.begin().
llvm::StringRef Qualifier;
// Heuristically parses before Offset to determine what should be completed.
CompletionPrefix guessCompletionPrefix(llvm::StringRef Content,
unsigned Offset);
// Whether it makes sense to complete at the point based on typed characters.
// For instance, we implicitly trigger at `a->^` but not at `a>^`.
bool allowImplicitCompletion(llvm::StringRef Content, unsigned Offset);
} // namespace clangd
} // namespace clang