swift-index-store is collection of libraries and tools for programmatically reading the source code index produced by swiftc and clang.

Example Usage

The IndexStore library is the primary entrypoint. For example if you want to print all the classes defined in a specific file:

let storePath = // path/to/DerivedData/index/store
let sourceFile = // path/to/interesting/source/file

// Load the index store produced by swiftc
let store = try IndexStore(path: storePath)
for unit in store.units {
    // Find the unit that corresponds to the source file we're interested in
    guard unit.mainFile == sourceFile, let recordName = unit.recordName else {

    let recordReader = try RecordReader(indexStore: store, recordName: recordName)
    recordReader.forEach { symbolOccurrence in
        // Print class definitions in the source file
        if symbolOccurrence.roles.contains(.definition) && symbolOccurrence.symbol.kind == .class {

For more examples see:

  • unnecessary-testable which discovers uses of @testable that aren’t required based on the API being called by the importing file.
  • tycat which print the subtypes or supertypes of a given type.
  • indexutil-annotate which outputs the index information overlaid on the given source file for debugging unexpected index data.


Swift Package Manager:

let package = Package(
    // ...
    dependencies: [
        .package(url: "https://github.com/lyft/swift-index-store", from: "1.0.0"),
    targets: [
        .executableTarget(name: "<command-line-tool>", dependencies: [
            .product(name: "IndexStore", package: "swift-index-store"),

How it works

During compilation, both swiftc and clang can generate a detailed source code index by providing the -index-store-path flag. The data model of the index is public, just not well known or well documented.

IndexStore is a Swift wrapper over the first party libIndexStore C library which is part of LLVM. Xcode and Swift for Linux contain libIndexStore, but its header is found separately in apple/llvm-project’s indexstore.h.

For more details on the index store’s data model, see:

  1. Adding Index-While-Building and Refactoring to Clang: https://www.youtube.com/watch?v=jGJhnIT-D2M
  2. High level design: https://docs.google.com/document/d/1cH2sTpgSnJZCkZtJl1aY-rzy4uGPcrI-6RrUpdATO2Q/

How does this differ from indexstore-db

The goal of this library is to provide a thin Swift layer on top of the C library for one shot tools that manage the structure of the index data themselves. indexstore-db provides more comprehensive support for querying index data as it changes across multiple builds.


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