Add struct declaration builder

Author: akkyie

Sources/SwiftSyntaxBuilder/Declarations/Buildables/Struct.swift

@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 Struct: DeclBuildable {
+  let name: String
+  let memberList: DeclListBuildable
+
+  public init(
+    _ name: String,
+    @DeclListBuilder buildMemberList: () -> DeclListBuildable = { DeclList.empty }
+  ) {
+    self.name = name
+    self.memberList = buildMemberList()
+  }
+
+  public func buildDecl(format: Format, leadingTrivia: Trivia) -> DeclSyntax {
+    let structKeyword = Tokens.struct.withLeadingTrivia(leadingTrivia + format.makeIndent())
+
+    let declList = memberList.buildDeclList(
+      format: format.indented(),
+      leadingTrivia: .newlines(1)
+    )
+
+    return StructDeclSyntax {
+      $0.useStructKeyword(structKeyword)
+      $0.useIdentifier(SyntaxFactory.makeIdentifier(name))
+      $0.useMembers(MemberDeclBlockSyntax {
+        $0.useLeftBrace(Tokens.leftBrace.withLeadingTrivia(.spaces(1)))
+        $0.useRightBrace(Tokens.rightBrace.withLeadingTrivia(.newlines(1) + format.makeIndent()))
+
+        for decl in declList {
+          $0.addMember(SyntaxFactory.makeMemberDeclListItem(decl: decl, semicolon: nil))
+        }
+      })
+    }
+  }
+}

Sources/SwiftSyntaxBuilder/Tokens/Tokens.swift

@@ -22,6 +22,9 @@ enum Tokens {
   /// `"var "`
   static let `var` = SyntaxFactory.makeVarKeyword().withTrailingTrivia(.spaces(1))
 
+  /// `"struct "`
+  static let `struct` = SyntaxFactory.makeStructKeyword().withTrailingTrivia(.spaces(1))
+
   // MARK: Punctuations and Signs
 
   /// `":"`
@@ -30,4 +33,10 @@ enum Tokens {
   /// `" = "`
   static let equal = SyntaxFactory.makeEqualToken().withLeadingTrivia(.spaces(1))
                                                    .withTrailingTrivia(.spaces(1))
+
+  /// `"{"`
+  static let leftBrace = SyntaxFactory.makeLeftBraceToken()
+
+  /// `"}"`
+  static let rightBrace = SyntaxFactory.makeRightBraceToken()
 }

Tests/SwiftSyntaxBuilderTest/Declarations/StructTests.swift

@@ -0,0 +1,41 @@
+import XCTest
+import SwiftSyntax
+
+@testable import SwiftSyntaxBuilder
+
+final class StructTests: XCTestCase {
+  let format = Format(indentWidth: 2).indented()
+
+  func testStruct() {
+    let testCases: [UInt: (Struct, String)] = [
+      #line: (
+        Struct("TestStruct"),
+        """
+          struct TestStruct {
+          }
+        """
+      ),
+
+      #line: (
+        Struct("TestStruct") {
+          Let("name", of: "String")
+        },
+        """
+          struct TestStruct {
+            let name: String
+          }
+        """
+      ),
+    ]
+
+    for (line, testCase) in testCases {
+      let (builder, expected) = testCase
+      let syntax = builder.buildSyntax(format: format, leadingTrivia: .zero)
+
+      var text = ""
+      syntax.write(to: &text)
+
+      XCTAssertEqual(text, expected, line: line)
+    }
+  }
+}