Swiftly Swift manipulation... with Swift FrenchKit 2019 Marcin Krzyzanowski

Agenda • Problem • Introduce SwiftSyntax • github.com/krzyzanowskim/reorder • IndexSourceDB

PROBLEM https://twitter.com/krzyzanowskim/status/1162306459075588096

import Foundation public class Conference { public var name: String public let venue: String INPUT

public class Conference { public var name: String public let venue: String internal typealias Line = String private var attendees: Set private var sponsors: Set private var costs: Array internal func add(attendee: String) internal func add(sponsor: String) deinit internal func add(cost: Decimal) private init() public func totalCosts() -> Decimal private func statement() -> Array internal func printStatement() public init(name: String, venue: String) } API

public class Conference { public var name: String public let venue: String internal typealias Line = String private var attendees: Set private var sponsors: Set private var costs: Array public init(name: String, venue: String) private init() deinit public func totalCosts() -> Decimal internal func add(attendee: String) internal func add(sponsor: String) internal func add(cost: Decimal) internal func printStatement() private func statement() -> Array } API Initializer Public Internal Private

public class Conference { public var name: String public let venue: String internal typealias Line = String private var attendees: Set private var sponsors: Set private var costs: Array internal func add(attendee: String) internal func add(sponsor: String) deinit internal func add(cost: Decimal) private init() public func totalCosts() -> Decimal private func statement() -> Array internal func printStatement() public init(name: String, venue: String) } public class Conference { public var name: String public let venue: String internal typealias Line = String private var attendees: Set private var sponsors: Set private var costs: Array public init(name: String, venue: String) private init() deinit public func totalCosts() -> Decimal internal func add(attendee: String) internal func add(sponsor: String) internal func add(cost: Decimal) internal func printStatement() private func statement() -> Array } →

HOW? move lines by hand use editor plugin use existing command line tool write a tool by my own

HOW? move lines by hand use editor plugin use existing command line tool write a tool by my own

HOW? move lines by hand use editor plugin use existing command line tool write a tool by my own

HOW? move lines by hand use editor plugin use existing command line tool write a tool by my own nicklockwood/SwiftFormat google/swift (format) inamiy/SwiftRewriter

HOW? move lines by hand use editor plugin use existing command line tool write a tool by my own

HOW? HOW? write a tool by my own Brain + Time + Computer + Programming Language + Library + ⏲ + + C +

you have brain

The Internet

SwiftSyntax github.com/apple/swift-syntax Source Code text/plain Abstract Syntax Tree

SwiftSyntax github.com/apple/swift-syntax Abstract Syntax Tree Syntax Syntax Syntax Syntax Syntax Syntax

SwiftSyntax Syntax Syntax Syntax Syntax Syntax Syntax Visitor Design Pattern The visitor design pattern is a way of separating an algorithm from an object structure on which it operates

SwiftSyntax import SwiftSyntax struct Visitor: SyntaxVisitor { mutating func visit(_ node: InitializerDeclSyntax) -> SyntaxVisitorContinueKind { self.process(node) return .skipChildren } }

SwiftSyntax class Rewriter: SyntaxRewriter { init() { } override func visit(_ node: DeinitializerDeclSyntax) -> DeclSyntax { return SyntaxFactory.makeBlankClassDecl() } }

PLAN 1. Search for all declarations (func, init, deinit) 2. Sort functions by access level and kind 3. Rewrite source with new order 4. Output source code

class Indexer: SyntaxVisitor { private var functions: Array = [] func visit(_ node: DeinitializerDeclSyntax) -> SyntaxVisitorContinueKind{ self.functions.append(node) return .skipChildren } func visit(_ node: InitializerDeclSyntax) -> SyntaxVisitorContinueKind { self.functions.append(node) return .skipChildren } func visit(_ node: FunctionDeclSyntax) -> SyntaxVisitorContinueKind { self.functions.append(node) return .skipChildren } } Indexer 1. Search for all declarations (func, init, deinit)

func sorted() -> Array { Sort 2. Sort functions by access level and kind

Rewrite class Rewriter: SyntaxRewriter { private let indexer: Indexer private var sortedFunctions: Array init(_ indexer: Indexer) { self.indexer = indexer self.sortedFunctions = indexer.sorted() } override func visit(_ node: DeinitializerDeclSyntax) -> DeclSyntax { sortedFunctions.removeFirst() } override func visit(_ node: InitializerDeclSyntax) -> DeclSyntax { sortedFunctions.removeFirst() } override func visit(_ node: FunctionDeclSyntax) -> DeclSyntax { sortedFunctions.removeFirst() } } 3. Rewrite source with new order

public func process(_ data: Data) throws -> String { guard let source = String(data: data, encoding: .utf8) else { throw Error.invalidInput } let parsed: SourceFileSyntax = try SyntaxParser.parse(source: source) // Gather information about the file var visitor = Indexer() parsed.walk(&visitor) // Rewrite file using visitor let rewritten = Rewriter(visitor).visit(parsed) var output = StringOutputStream() rewritten.write(to: &output) return output.string } Processor 4. Output source code

// // swift run reorder -file Sources/Conference/Conference.swift > output.swift // guard let executablePath = CommandLine.arguments.first else { fatalError("Missing executable") } let args = Array(CommandLine.arguments.dropFirst()) let commands = stride(from: 0, to: args.count - 1, by: 2).map { (command: args[$0].dropFirst(), value: args[$0+1]) } var err = StderrOutputStream() var out = StdoutOutputStream() for (cmd, value) in commands { switch cmd { case "file": err.write("Processing \(value)\n") let content = try Data(contentsOf: URL(fileURLWithPath: value)) let result = try Processor().process(content) out.write(result) break default: err.write("Error: Unknown command: \(cmd)\n") $ ./reorder -file Conference.swift

import Foundation public class Conference { public var name: String public let venue: String internal typealias Line = String private var attendees: Set private var sponsors: Set private var costs: Array public init(name: String, venue: String) { self.name = name self.venue = venue self.attendees = [] self.sponsors = [] self.costs = [] } private init() { self.name = "FrenchKit" self.venue = "Bâtiment" self.attendees = [] $ ./reorder -file Conference.swift

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• Sort class/struct properties • Sort within extension scope • Sort static func/property HOMEWORK github.com/krzyzanowskim/reorder Submit Pull Request!

ONE MORE THING

IndexStoreDB IndexStoreDB is a source code indexing library. It provides a composable and efficient query API for looking up source code symbols, symbol occurrences, and relations. github.com/apple/indexstore-db

IndexStoreDB IndexStoreDB is a source code indexing library. It provides a composable and efficient query API for looking up source code symbols, symbol occurrences, and relations. github.com/apple/indexstore-db swift build --enable-index-store .build/x86_64-apple-macosx/debug/index/store

IndexStoreDB github.com/apple/indexstore-db $ swiftc -index-store-path index -index-file Sources/Conference/Conference.swift

StoreIndexer public struct StoreIndexer { public typealias Path = String public struct Function { public let symbol: Symbol public let location: SymbolLocation } private let indexURL: URL

IndexStoreDB 1. StoreIndexer fetch all files where Conference occurs 2. SwiftSyntax process files and output

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ONE MISSING THING //===-------------------------------------------------------===// // SourceKit README //===-------------------------------------------------------===// Welcome to SourceKit! SourceKit is a framework for supporting IDE features like indexing, syntax-coloring, code-completion, etc. In general it provides the infrastructure that an IDE needs for excellent language support. SourceKit currently only supports the Swift language.

LINKS Building a Compiler in Swift - Nick Lockwood https://www.youtube.com/watch?v=uQNkrV0F07Q N. Hawes & A. Lorenz “Adding Index‐While‐Building and ..." https://www.youtube.com/watch?v=jGJhnIT-D2M Creating Refactoring Transformations for Swift https://www.skilled.io/u/swiftsummit/creating-refactoring-transformations-for-swift NSHipster - Swift Syntax https://nshipster.com/swiftsyntax/ reorder https://github.com/krzyzanowskim/reorder

THANK YOU @krzyzanowskim github.com/krzyzanowskim https://swift.best