From b86cb77685325f7d5b13e4d69fee6cb8a3444696 Mon Sep 17 00:00:00 2001
From: Natik Gadzhi <natik@respawn.io>
Date: Sun, 2 Jul 2023 21:21:11 -0700
Subject: [PATCH] Allow anchor <doc:#heading> within same article

---
 .../Link Resolution/PathHierarchy.swift       | 10 ++++++--
 .../Infrastructure/PathHierarchyTests.swift   | 25 +++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/Sources/SwiftDocC/Infrastructure/Link Resolution/PathHierarchy.swift b/Sources/SwiftDocC/Infrastructure/Link Resolution/PathHierarchy.swift
index f6842763f3..87d5ac8fcf 100644
--- a/Sources/SwiftDocC/Infrastructure/Link Resolution/PathHierarchy.swift	
+++ b/Sources/SwiftDocC/Infrastructure/Link Resolution/PathHierarchy.swift	
@@ -764,10 +764,16 @@ extension PathHierarchy {
         let isAbsolute = path.first == "/"
             || String(components.first ?? "") == NodeURLGenerator.Path.documentationFolderName
             || String(components.first ?? "") == NodeURLGenerator.Path.tutorialsFolderName
-       
+
+        // If there is a # character in the last component, split that into two components
         if let hashIndex = components.last?.firstIndex(of: "#") {
             let last = components.removeLast()
-            components.append(last[..<hashIndex])
+            // Allow anrhor-only links where there's nothing before #.
+            // In case the pre-# part is empty, and we're omitting empty components, don't add it in.
+            let pathName = last[..<hashIndex]
+            if !pathName.isEmpty || !omittingEmptyComponents {
+                components.append(pathName)
+            }
             
             let fragment = String(last[hashIndex...].dropFirst())
             return (components.map(Self.parse(pathComponent:)) + [PathComponent(full: fragment, name: fragment, kind: nil, hash: nil)], isAbsolute)
diff --git a/Tests/SwiftDocCTests/Infrastructure/PathHierarchyTests.swift b/Tests/SwiftDocCTests/Infrastructure/PathHierarchyTests.swift
index d31de01a40..dedde1ab95 100644
--- a/Tests/SwiftDocCTests/Infrastructure/PathHierarchyTests.swift
+++ b/Tests/SwiftDocCTests/Infrastructure/PathHierarchyTests.swift
@@ -1133,6 +1133,30 @@ class PathHierarchyTests: XCTestCase {
         XCTAssertNil(articleNode.symbol, "General documentation link find the article")
     }
     
+    func testArticleSelfAnchorLinks() throws {
+        try XCTSkipUnless(LinkResolutionMigrationConfiguration.shouldUseHierarchyBasedLinkResolver)
+        let (_, _, context) = try testBundleAndContext(copying: "MixedLanguageFramework") { url in
+            try """
+            # ArticleWithHeading
+
+            ## TestTargetHeading
+
+            This article has the same path as a symbol. See also:
+            - <doc:TestTargetHeading>
+            - <doc:#TestTargetHeading>
+
+            """.write(to: url.appendingPathComponent("ArticleWithHeading.md"), atomically: true, encoding: .utf8)
+        }
+
+        let tree = try XCTUnwrap(context.hierarchyBasedLinkResolver?.pathHierarchy)
+        let articleNode = try tree.findNode(path: "/MixedLanguageFramework/ArticleWithHeading", onlyFindSymbols: false)
+
+        let linkNode = try tree.find(path: "TestTargetHeading", parent: articleNode.identifier, onlyFindSymbols: false)
+        let anchorLinkNode = try tree.find(path: "#TestTargetHeading", parent: articleNode.identifier, onlyFindSymbols: false)
+        XCTAssertNotNil(linkNode)
+        XCTAssertNotNil(anchorLinkNode)
+    }
+
     func testOverloadedSymbols() throws {
         try XCTSkipUnless(LinkResolutionMigrationConfiguration.shouldUseHierarchyBasedLinkResolver)
         let (_, context) = try testBundleAndContext(named: "OverloadedSymbols")
@@ -1555,6 +1579,7 @@ class PathHierarchyTests: XCTestCase {
         assertParsedPathComponents("first/", [("first", nil, nil)])
         assertParsedPathComponents("first//second", [("first", nil, nil), ("second", nil, nil)])
         assertParsedPathComponents("first/second#third", [("first", nil, nil), ("second", nil, nil), ("third", nil, nil)])
+        assertParsedPathComponents("#first", [("first", nil, nil)])
 
         // Check disambiguation
         assertParsedPathComponents("path-hash", [("path", nil, "hash")])