From a54c1644586945bf2a1487bdc732b0a5f01c8621 Mon Sep 17 00:00:00 2001
From: Sofia Rodriguez Morales <sofia_rodriguez@apple.com>
Date: Mon, 13 Oct 2025 18:44:53 +0100
Subject: [PATCH] Don't decode empty bystander arrays.

If a bystandar array is empty after decoding it don't initialize the value.

Usally this wouldn't happen, but if it does, it can break DocC.

rdar://162596256
---
 Sources/SymbolKit/SymbolGraph/Module.swift         | 6 ++++--
 Tests/SymbolKitTests/SymbolGraph/ModuleTests.swift | 7 +++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Sources/SymbolKit/SymbolGraph/Module.swift b/Sources/SymbolKit/SymbolGraph/Module.swift
index a5115a8..7b077da 100644
--- a/Sources/SymbolKit/SymbolGraph/Module.swift
+++ b/Sources/SymbolKit/SymbolGraph/Module.swift
@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2025 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
@@ -40,7 +40,9 @@ extension SymbolGraph {
         public init(from decoder: Decoder) throws {
             let container = try decoder.container(keyedBy: CodingKeys.self)
             self.name = try container.decode(String.self, forKey: .name)
-            self.bystanders = try container.decodeIfPresent([String].self, forKey: .bystanders)
+            if let bystanders = try container.decodeIfPresent([String].self, forKey: .bystanders) {
+                self.bystanders = bystanders.isEmpty ? nil : bystanders
+            }
             self.platform = try container.decode(Platform.self, forKey: .platform)
             self.version = try container.decodeIfPresent(SemanticVersion.self, forKey: .version)
             self.isVirtual = try container.decodeIfPresent(Bool.self, forKey: .isVirtual) ?? false
diff --git a/Tests/SymbolKitTests/SymbolGraph/ModuleTests.swift b/Tests/SymbolKitTests/SymbolGraph/ModuleTests.swift
index ab407e3..4ff7f50 100644
--- a/Tests/SymbolKitTests/SymbolGraph/ModuleTests.swift
+++ b/Tests/SymbolKitTests/SymbolGraph/ModuleTests.swift
@@ -44,6 +44,13 @@ class ModuleTests: XCTestCase {
             let decodedModule = try module.roundTripDecode()
             XCTAssertEqual(["A"], decodedModule.bystanders)
         }
+        
+        do {
+            // bystanders = []
+            let module = SymbolGraph.Module(name: "Test", platform: ModuleTests.platform, bystanders: [])
+            let decodedModule = try module.roundTripDecode()
+            XCTAssertNil(decodedModule.bystanders)
+        }
     }
     
     func testOptionalIsVirtual() throws {