[Feature] Custom list prefixes for AttributedStringVisitor

.travis.yml

@@ -4,9 +4,9 @@ before_install:
   - set -o pipefail
   - xcrun simctl boot "iPhone 12" || echo "(Pre)Launched the simulator."
 script:
-  - travis_retry xcodebuild -project Down.xcodeproj -scheme "Down" -sdk iphonesimulator -destination "platform=iOS Simulator,OS=14.2,name=iPhone 12" -enableCodeCoverage YES ONLY_ACTIVE_ARCH=YES test
+  - travis_retry xcodebuild -project Down.xcodeproj -scheme "Down" -sdk iphonesimulator -destination "platform=iOS Simulator,OS=14.2,name=iPhone 12" -enableCodeCoverage YES ONLY_ACTIVE_ARCH=YES -quiet test
   - bash <(curl -s https://codecov.io/bash)
-  - travis_retry xcodebuild -project Down.xcodeproj -scheme "Down" -sdk macosx -destination 'platform=OS X,arch=x86_64' -enableCodeCoverage YES test
+  - travis_retry xcodebuild -project Down.xcodeproj -scheme "Down" -sdk macosx -destination 'platform=OS X,arch=x86_64' -enableCodeCoverage YES -quiet test
   - bash <(curl -s https://codecov.io/bash) 
-  - travis_retry xcodebuild -project Down.xcodeproj -scheme "Down" -sdk appletvsimulator -destination 'platform=tvOS Simulator,name=Apple TV' -enableCodeCoverage YES test
+  - travis_retry xcodebuild -project Down.xcodeproj -scheme "Down" -sdk appletvsimulator -destination 'platform=tvOS Simulator,name=Apple TV' -enableCodeCoverage YES -quiet test
   - bash <(curl -s https://codecov.io/bash)

Sources/Down/AST/Visitors/AttributedStringVisitor.swift

@@ -14,23 +14,32 @@ import Foundation
 /// represented at each node and uses an instance of `Styler` to apply the visual attributes.
 /// These substrings are joined together to produce the final result.
 
+public typealias ListPrefixGeneratorBuilder = (List) -> ListItemPrefixGenerator
+
 public class AttributedStringVisitor {
 
     // MARK: - Properties
 
     private let styler: Styler
     private let options: DownOptions
+    private let listPrefixGeneratorBuilder: ListPrefixGeneratorBuilder
     private var listPrefixGenerators = [ListItemPrefixGenerator]()
 
     /// Creates a new instance with the given styler and options.
     ///
     /// - parameters:
     ///     - styler: used to style the markdown elements.
     ///     - options: may be used to modify rendering.
+    ///     - listPrefixGeneratorBuilder: may be used to modify list prefixes.
 
-    public init(styler: Styler, options: DownOptions = .default) {
+    public init(
+        styler: Styler,
+        options: DownOptions = .default,
+        listPrefixGeneratorBuilder: @escaping ListPrefixGeneratorBuilder = { StaticListItemPrefixGenerator(list: $0) }
+    ) {
         self.styler = styler
         self.options = options
+        self.listPrefixGeneratorBuilder = listPrefixGeneratorBuilder
     }
 
 }
@@ -53,7 +62,8 @@ extension AttributedStringVisitor: Visitor {
     }
 
     public func visit(list node: List) -> NSMutableAttributedString {
-        listPrefixGenerators.append(ListItemPrefixGenerator(list: node))
+
+        listPrefixGenerators.append(listPrefixGeneratorBuilder(node))
         defer { listPrefixGenerators.removeLast() }
 
         let items = visitChildren(of: node)

Sources/Down/AST/Visitors/ListItemPrefixGenerator.swift

@@ -8,34 +8,46 @@
 
 import Foundation
 
-class ListItemPrefixGenerator {
+/// A ListItemPrefixGenerator is an object used to generate list item prefix.
+public protocol ListItemPrefixGenerator {
+    init(listType: List.ListType, numberOfItems: Int, nestDepth: Int)
+    func next() -> String?
+}
+
+public extension ListItemPrefixGenerator {
+    init(list: List) {
+        self.init(listType: list.listType, numberOfItems: list.numberOfItems, nestDepth: list.nestDepth)
+    }
+}
+
+/// Default implementation of `ListItemPrefixGenerator`.
+/// Generating the following symbol based on `List.ListType`:
+/// - List.ListType is bullet => "•"
+/// - List.ListType is ordered => "X." (where is the item number)
+public class StaticListItemPrefixGenerator: ListItemPrefixGenerator {
 
     // MARK: - Properties
 
     private var prefixes: IndexingIterator<[String]>
 
     // MARK: - Life cycle
 
-    convenience init(list: List) {
-        self.init(listType: list.listType, numberOfItems: list.numberOfItems)
-    }
-
-    init(listType: List.ListType, numberOfItems: Int) {
-        switch listType {
-        case .bullet:
-            prefixes = [String](repeating: "•", count: numberOfItems)
-                .makeIterator()
-
-        case .ordered(let start):
-            prefixes = (start..<(start + numberOfItems))
-                .map { "\($0)." }
-                .makeIterator()
+    required public init(listType: List.ListType, numberOfItems: Int, nestDepth: Int) {
+            switch listType {
+            case .bullet:
+                prefixes = [String](repeating: "•", count: numberOfItems)
+                    .makeIterator()
+
+            case .ordered(let start):
+                prefixes = (start..<(start + numberOfItems))
+                    .map { "\($0)." }
+                    .makeIterator()
+            }
         }
-    }
 
     // MARK: - Methods
 
-    func next() -> String? {
+    public func next() -> String? {
         prefixes.next()
     }
 

Tests/DownTests/AST/ListItemPrefixGeneratorTests.swift

@@ -11,9 +11,9 @@ import XCTest
 
 class ListItemPrefixGeneratorTests: XCTestCase {
 
-    func testNumberPrefixGeneration() {
+    func testNumberStaticPrefixGeneration() {
         // Given
-        let sut = ListItemPrefixGenerator(listType: .ordered(start: 3), numberOfItems: 3)
+        let sut = StaticListItemPrefixGenerator(listType: .ordered(start: 3), numberOfItems: 3, nestDepth: 1)
 
         // Then
         XCTAssertEqual("3.", sut.next())
@@ -22,9 +22,9 @@ class ListItemPrefixGeneratorTests: XCTestCase {
         XCTAssertNil(sut.next())
     }
 
-    func testBulletPrefixGeneration() {
+    func testBulletStaticPrefixGeneration() {
         // Given
-        let sut = ListItemPrefixGenerator(listType: .bullet, numberOfItems: 3)
+        let sut = StaticListItemPrefixGenerator(listType: .bullet, numberOfItems: 3, nestDepth: 1)
 
         // Then
         XCTAssertEqual("•", sut.next())