Fix custom doc link title issue

Sources/SwiftDocC/Model/Rendering/RenderContentCompiler.swift

@@ -165,7 +165,30 @@ struct RenderContentCompiler: MarkupVisitor {
             return [RenderInlineContent.text(link.plainText)]
         }
 
-        return [RenderInlineContent.reference(identifier: .init(resolved.absoluteString), isActive: true, overridingTitle: nil, overridingTitleInlineContent: nil)]
+        let linkTitleInlineContent = link.children.flatMap { visit($0) } as! [RenderInlineContent]
+        let plainTextLinkTitle = linkTitleInlineContent.plainText
+        let overridingTitle = plainTextLinkTitle.isEmpty ? nil : plainTextLinkTitle
+        let overridingTitleInlineContent = linkTitleInlineContent.isEmpty ? nil : linkTitleInlineContent
+
+        let useOverriding: Bool
+        if link.isAutolink { // If the link is an auto link, we don't use overriding info
+            useOverriding = false
+        } else if let overridingTitle = overridingTitle,
+                  overridingTitle.hasPrefix(ResolvedTopicReference.urlScheme + ":"),
+                  destination.hasPrefix(ResolvedTopicReference.urlScheme + "://"),
+                  destination.hasSuffix(overridingTitle.dropFirst((ResolvedTopicReference.urlScheme + ":").count)) { // If the link is a transformed doc link, we don't use overriding info
+            useOverriding = false
+        } else {
+            useOverriding = true
+        }
+        return [
+            RenderInlineContent.reference(
+                identifier: .init(resolved.absoluteString),
+                isActive: true,
+                overridingTitle: useOverriding ? overridingTitle : nil,
+                overridingTitleInlineContent: useOverriding ? overridingTitleInlineContent : nil
+            )
+        ]
     }
 
     mutating func resolveTopicReference(_ destination: String) -> ResolvedTopicReference? {
@@ -194,7 +217,7 @@ struct RenderContentCompiler: MarkupVisitor {
     func resolveSymbolReference(destination: String) -> ResolvedTopicReference? {
         if let cached = context.documentationCacheBasedLinkResolver.referenceFor(absoluteSymbolPath: destination, parent: identifier) {
             return cached
-        } 
+        }
 
         // The symbol link may be written with a scheme and bundle identifier.
         let url = ValidatedURL(parsingExact: destination)?.requiring(scheme: ResolvedTopicReference.urlScheme) ?? ValidatedURL(symbolPath: destination)

Tests/SwiftDocCTests/Rendering/RenderContentCompilerTests.swift

@@ -0,0 +1,134 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2023 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 Swift project authors
+*/
+
+import Foundation
+import Markdown
+@testable import SwiftDocC
+import XCTest
+
+class RenderContentCompilerTests: XCTestCase {
+    func testLinkOverrideTitle() throws {
+        let (bundle, context) = try testBundleAndContext(named: "TestBundle")
+        var compiler = RenderContentCompiler(context: context, bundle: bundle, identifier: ResolvedTopicReference(bundleIdentifier: bundle.identifier, path: "/path", fragment: nil, sourceLanguage: .swift))
+
+        let source = """
+        [Example](http://example.com)
+
+        [Custom Title](doc:UNRESOVLED)
+
+        [Custom Title](doc:article)
+
+        [Custom Image Content ![random image](https://example.com/test.png)](doc:article2)
+
+        <doc:UNRESOVLED>
+
+        <doc:article3>
+        """
+        let document = Document(parsing: source)
+        let expectedDump = """
+        Document
+        ├─ Paragraph
+        │  └─ Link destination: "http://example.com"
+        │     └─ Text "Example"
+        ├─ Paragraph
+        │  └─ Link destination: "doc:UNRESOVLED"
+        │     └─ Text "Custom Title"
+        ├─ Paragraph
+        │  └─ Link destination: "doc:article"
+        │     └─ Text "Custom Title"
+        ├─ Paragraph
+        │  └─ Link destination: "doc:article2"
+        │     ├─ Text "Custom Image Content "
+        │     └─ Image source: "https://example.com/test.png" title: ""
+        │        └─ Text "random image"
+        ├─ Paragraph
+        │  └─ Link destination: "doc:UNRESOVLED"
+        │     └─ Text "doc:UNRESOVLED"
+        └─ Paragraph
+           └─ Link destination: "doc:article3"
+              └─ Text "doc:article3"
+        """
+        XCTAssertEqual(document.debugDescription(), expectedDump)
+
+        let result = document.children.flatMap { compiler.visit($0) }
+        XCTAssertEqual(result.count, 6)
+
+        do {
+            guard case let .paragraph(paragraph) = result[0] as? RenderBlockContent else {
+                XCTFail("RenderCotent result is not the expected RenderBlockContent.paragraph(Paragraph)")
+                return
+            }
+            let link = RenderInlineContent.reference(
+                identifier: .init(forExternalLink: "http://example.com"),
+                isActive: true,
+                overridingTitle: nil,
+                overridingTitleInlineContent: nil
+            )
+            XCTAssertEqual(paragraph, RenderBlockContent.Paragraph(inlineContent: [link]))
+        }
+        do {
+            guard case let .paragraph(paragraph) = result[1] as? RenderBlockContent else {
+                XCTFail("RenderCotent result is not the expected RenderBlockContent.paragraph(Paragraph)")
+                return
+            }
+            let text = RenderInlineContent.text("Custom Title")
+            XCTAssertEqual(paragraph, RenderBlockContent.Paragraph(inlineContent: [text]))
+        }
+        do {
+            guard case let .paragraph(paragraph) = result[2] as? RenderBlockContent else {
+                XCTFail("RenderCotent result is not the expected RenderBlockContent.paragraph(Paragraph)")
+                return
+            }
+            let link = RenderInlineContent.reference(
+                identifier: .init("doc://org.swift.docc.example/documentation/Test-Bundle/article"),
+                isActive: true,
+                overridingTitle: "Custom Title",
+                overridingTitleInlineContent: [.text("Custom Title")])
+            XCTAssertEqual(paragraph, RenderBlockContent.Paragraph(inlineContent: [link]))
+        }
+        do {
+            guard case let .paragraph(paragraph) = result[3] as? RenderBlockContent else {
+                XCTFail("RenderCotent result is not the expected RenderBlockContent.paragraph(Paragraph)")
+                return
+            }
+            let link = RenderInlineContent.reference(
+                identifier: .init("doc://org.swift.docc.example/documentation/Test-Bundle/article2"),
+                isActive: true,
+                overridingTitle: "Custom Image Content ",
+                overridingTitleInlineContent: [
+                    RenderInlineContent.text("Custom Image Content "),
+                    RenderInlineContent.image(identifier: .init(forExternalLink: "https://example.com/test.png"), metadata: nil)
+                ]
+            )
+            XCTAssertEqual(paragraph, RenderBlockContent.Paragraph(inlineContent: [link]))
+        }
+        do {
+            guard case let .paragraph(paragraph) = result[4] as? RenderBlockContent else {
+                XCTFail("RenderCotent result is not the expected RenderBlockContent.paragraph(Paragraph)")
+                return
+            }
+            let text = RenderInlineContent.text("doc:UNRESOVLED")
+            XCTAssertEqual(paragraph, RenderBlockContent.Paragraph(inlineContent: [text]))
+        }
+        do {
+            guard case let .paragraph(paragraph) = result[5] as? RenderBlockContent else {
+                XCTFail("RenderCotent result is not the expected RenderBlockContent.paragraph(Paragraph)")
+                return
+            }
+            let link = RenderInlineContent.reference(
+                identifier: .init("doc://org.swift.docc.example/documentation/Test-Bundle/article3"),
+                isActive: true,
+                overridingTitle: nil,
+                overridingTitleInlineContent: nil
+            )
+            XCTAssertEqual(paragraph, RenderBlockContent.Paragraph(inlineContent: [link]))
+        }
+    }
+}