From 855d8b07dc68012a907521ceeb4926331cbcecba Mon Sep 17 00:00:00 2001
From: Artem Chikin <achikin@apple.com>
Date: Mon, 18 Mar 2024 10:23:10 -0700
Subject: [PATCH] [Explicit Module Builds] When '-explain-module-dependency'
 encounters the target Swift module, continue enumerating other possible paths

---
 .../CommonDependencyOperations.swift                  | 11 +++++------
 Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift |  1 +
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/CommonDependencyOperations.swift b/Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/CommonDependencyOperations.swift
index a4c742a07..eaad3543d 100644
--- a/Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/CommonDependencyOperations.swift
+++ b/Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/CommonDependencyOperations.swift
@@ -252,22 +252,22 @@ extension InterModuleDependencyGraph {
 internal extension InterModuleDependencyGraph {
   func explainDependency(dependencyModuleName: String) throws -> [[ModuleDependencyId]]? {
     guard modules.contains(where: { $0.key.moduleName == dependencyModuleName }) else { return nil }
-    var results = [[ModuleDependencyId]]()
+    var results = Set<[ModuleDependencyId]>()
     try findAllPaths(source: .swift(mainModuleName),
                      to: dependencyModuleName,
                      pathSoFar: [.swift(mainModuleName)],
                      results: &results)
-    return Array(results)
+    return results.sorted(by: { $0.count < $1.count })
   }
 
 
   private func findAllPaths(source: ModuleDependencyId,
                             to moduleName: String,
                             pathSoFar: [ModuleDependencyId],
-                            results: inout [[ModuleDependencyId]]) throws {
+                            results: inout Set<[ModuleDependencyId]>) throws {
     let sourceInfo = try moduleInfo(of: source)
     // If the source is our target, we are done
-    guard source.moduleName != moduleName else {
+    if source.moduleName == moduleName {
       // If the source is a target Swift module, also check if it
       // depends on a corresponding Clang module with the same name.
       // If it does, add it to the path as well.
@@ -276,8 +276,7 @@ internal extension InterModuleDependencyGraph {
          dependencies.contains(.clang(moduleName)) {
         completePath.append(.clang(moduleName))
       }
-      results.append(completePath)
-      return
+      results.insert(completePath)
     }
 
     var allDependencies = sourceInfo.directDependencies ?? []
diff --git a/Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift b/Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift
index 73e0719d3..a45831e4e 100644
--- a/Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift
+++ b/Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift
@@ -1923,6 +1923,7 @@ final class ExplicitModuleBuildTests: XCTestCase {
         print(diag.behavior)
         print(diag.message)
       }
+      XCTAssertEqual(driver.diagnosticEngine.diagnostics.filter { $0.behavior == .note}.count, 2)
       XCTAssertTrue(driver.diagnosticEngine.diagnostics.contains { $0.behavior == .note &&
                                                                    $0.message.text == "[testTraceDependency] -> [A] -> [A](ObjC)"})
       XCTAssertTrue(driver.diagnosticEngine.diagnostics.contains { $0.behavior == .note &&