Add types to build SwiftSyntax.Syntax

Author: akkyie

Sources/SwiftSyntaxBuilder/Format/Format.swift

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+public struct Format {
+  public let indentWidth: Int
+
+  private var indents: Int = 0
+
+  public init(indentWidth: Int = 4) {
+    self.indentWidth = indentWidth
+  }
+}
+
+extension Format {
+  func indented() -> Format {
+    var copy = self
+    copy.indents += 1
+    return copy
+  }
+
+  func makeIndent() -> Trivia {
+    return indents == 0 ? .zero : Trivia.spaces(indents * indentWidth)
+  }
+}

Sources/SwiftSyntaxBuilder/Syntax/SyntaxBuildable.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+public protocol SyntaxListBuildable {
+  func buildSyntaxList(format: Format, leadingTrivia: Trivia) -> [Syntax]
+}
+
+public protocol SyntaxBuildable: SyntaxListBuildable {
+  func buildSyntax(format: Format, leadingTrivia: Trivia) -> Syntax
+}
+
+extension SyntaxBuildable {
+  public func buildSyntaxList(format: Format, leadingTrivia: Trivia) -> [Syntax] {
+    [buildSyntax(format: format, leadingTrivia: leadingTrivia)]
+  }
+}

Sources/SwiftSyntaxBuilder/Syntax/SyntaxList.swift

@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+public struct SyntaxList: SyntaxListBuildable {
+  let builders: [SyntaxListBuildable]
+
+  public func buildSyntaxList(format: Format, leadingTrivia: Trivia) -> [Syntax] {
+    // Returns indented newlines to join syntaxes
+    func trivia(for index: Int) -> Trivia {
+      leadingTrivia + (index > builders.startIndex ? .newlines(1) : .zero)
+    }
+
+    return builders
+      .enumerated()
+      .flatMap { index, builder in
+        builder.buildSyntaxList(format: format, leadingTrivia: trivia(for: index))
+    }
+  }
+}
+
+extension SyntaxList {
+  public static let empty = SyntaxList(builders: [])
+}

Sources/SwiftSyntaxBuilder/Syntax/SyntaxListBuilder.swift

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+@_functionBuilder
+public struct SyntaxListBuilder {
+  public static func buildBlock(_ builders: SyntaxListBuildable...) -> SyntaxListBuildable {
+    SyntaxList(builders: builders)
+  }
+}

Tests/SwiftSyntaxBuilderTest/Format/FormatTests.swift

@@ -0,0 +1,16 @@
+import XCTest
+import SwiftSyntax
+
+@testable import SwiftSyntaxBuilder
+
+final class FormatTests: XCTestCase {
+  func testMakeIndented() {
+    for width in 1 ... 4 {
+      let format = Format(indentWidth: width)
+
+      XCTAssertEqual(format.makeIndent(), .zero)
+      XCTAssertEqual(format.indented().makeIndent(), .spaces(width))
+      XCTAssertEqual(format.indented().indented().makeIndent(), .spaces(width * 2))
+    }
+  }
+}