From 7d30401668b7a0de9f6d06a8e3b0afb2e8dbd633 Mon Sep 17 00:00:00 2001
From: Stefan Ceriu <stefan.ceriu@gmail.com>
Date: Wed, 30 Sep 2026 15:32:04 +0300
Subject: [PATCH] fix: serialize schemes the way Xcode does

Xcode rewrites schemes generated by XcodeProj as soon as it touches
them, which shows up as noise in projects that commit generated
schemes. Match Xcode's own output:

- Write `TestPlans` as the last child of `TestAction`.
- Omit an empty `Testables` element when the scheme uses test plans.
- Omit empty `CommandLineArguments` elements.
- Only write `runPostActionsOnFailure` when it is enabled.
- Write `TestPlanReference` attributes in Xcode's order (`reference`,
  then `default`).

Verified against a scheme re-saved by Xcode 27: regenerating it with
these changes produces a byte-identical file.
---
 .../xcshareddata/xcschemes/iOS.xcscheme       | 12 +++----
 .../Extensions/AEXML+XcodeFormat.swift        |  4 +++
 .../Scheme/XCScheme+BuildAction.swift         |  5 +--
 .../Scheme/XCScheme+LaunchAction.swift        |  2 +-
 .../Scheme/XCScheme+ProfileAction.swift       |  2 +-
 .../Scheme/XCScheme+TestAction.swift          | 25 ++++++++-------
 .../XcodeProjTests/Scheme/XCSchemeTests.swift | 31 +++++++++++++++++++
 7 files changed, 60 insertions(+), 21 deletions(-)

diff --git a/Fixtures/iOS/Project.xcodeproj/xcshareddata/xcschemes/iOS.xcscheme b/Fixtures/iOS/Project.xcodeproj/xcshareddata/xcschemes/iOS.xcscheme
index 5ec735651..1b4bc284c 100644
--- a/Fixtures/iOS/Project.xcodeproj/xcshareddata/xcschemes/iOS.xcscheme
+++ b/Fixtures/iOS/Project.xcodeproj/xcshareddata/xcschemes/iOS.xcscheme
@@ -81,12 +81,6 @@
             </ActionContent>
          </ExecutionAction>
       </PostActions>
-      <TestPlans>
-         <TestPlanReference
-            default = "YES"
-            reference = "container:iOS.xctestplan">
-         </TestPlanReference>
-      </TestPlans>
       <MacroExpansion>
          <BuildableReference
             BuildableIdentifier = "primary"
@@ -122,6 +116,12 @@
             isEnabled = "NO">
          </EnvironmentVariable>
       </EnvironmentVariables>
+      <TestPlans>
+         <TestPlanReference
+            reference = "container:iOS.xctestplan"
+            default = "YES">
+         </TestPlanReference>
+      </TestPlans>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"
diff --git a/Sources/XcodeProj/Extensions/AEXML+XcodeFormat.swift b/Sources/XcodeProj/Extensions/AEXML+XcodeFormat.swift
index 85f5bf96d..484fcc62d 100644
--- a/Sources/XcodeProj/Extensions/AEXML+XcodeFormat.swift
+++ b/Sources/XcodeProj/Extensions/AEXML+XcodeFormat.swift
@@ -86,6 +86,10 @@ let attributesOrder: [String: [String]] = [
         "value",
         "isEnabled",
     ],
+    "TestPlanReference": [
+        "reference",
+        "default",
+    ],
     "TestableReference": [
         "skipped",
         "parallelizable",
diff --git a/Sources/XcodeProj/Scheme/XCScheme+BuildAction.swift b/Sources/XcodeProj/Scheme/XCScheme+BuildAction.swift
index 8cc9ed15a..9a8228b3d 100644
--- a/Sources/XcodeProj/Scheme/XCScheme+BuildAction.swift
+++ b/Sources/XcodeProj/Scheme/XCScheme+BuildAction.swift
@@ -158,8 +158,9 @@ public extension XCScheme {
                 attributes["buildArchitectures"] = buildArchitecturesXMLString
             }
 
-            if let runPostActionsOnFailure {
-                attributes["runPostActionsOnFailure"] = runPostActionsOnFailure.xmlString
+            // Xcode omits the attribute unless it is enabled.
+            if runPostActionsOnFailure == true {
+                attributes["runPostActionsOnFailure"] = true.xmlString
             }
 
             let element = AEXMLElement(name: "BuildAction",
diff --git a/Sources/XcodeProj/Scheme/XCScheme+LaunchAction.swift b/Sources/XcodeProj/Scheme/XCScheme+LaunchAction.swift
index 5f73777bc..6fc783959 100644
--- a/Sources/XcodeProj/Scheme/XCScheme+LaunchAction.swift
+++ b/Sources/XcodeProj/Scheme/XCScheme+LaunchAction.swift
@@ -445,7 +445,7 @@ public extension XCScheme {
                 macro.addChild(macroExpansion.xmlElement())
             }
 
-            if let commandlineArguments {
+            if let commandlineArguments, !commandlineArguments.arguments.isEmpty {
                 element.addChild(commandlineArguments.xmlElement())
             }
 
diff --git a/Sources/XcodeProj/Scheme/XCScheme+ProfileAction.swift b/Sources/XcodeProj/Scheme/XCScheme+ProfileAction.swift
index f972cf76a..6f3872432 100644
--- a/Sources/XcodeProj/Scheme/XCScheme+ProfileAction.swift
+++ b/Sources/XcodeProj/Scheme/XCScheme+ProfileAction.swift
@@ -169,7 +169,7 @@ public extension XCScheme {
             if !enableTestabilityWhenProfilingTests {
                 element.attributes["enableTestabilityWhenProfilingTests"] = "No"
             }
-            if let commandlineArguments {
+            if let commandlineArguments, !commandlineArguments.arguments.isEmpty {
                 element.addChild(commandlineArguments.xmlElement())
             }
             if let environmentVariables {
diff --git a/Sources/XcodeProj/Scheme/XCScheme+TestAction.swift b/Sources/XcodeProj/Scheme/XCScheme+TestAction.swift
index 735e699b1..8a865a00a 100644
--- a/Sources/XcodeProj/Scheme/XCScheme+TestAction.swift
+++ b/Sources/XcodeProj/Scheme/XCScheme+TestAction.swift
@@ -204,24 +204,20 @@ public extension XCScheme {
             let element = AEXMLElement(name: "TestAction", value: nil, attributes: attributes)
             super.writeXML(parent: element)
 
-            if let testPlans {
-                let testPlansElement = element.addChild(name: "TestPlans")
-                for testPlan in testPlans {
-                    testPlansElement.addChild(testPlan.xmlElement())
-                }
-            }
-
             if let macroExpansion {
                 let macro = element.addChild(name: "MacroExpansion")
                 macro.addChild(macroExpansion.xmlElement())
             }
 
-            let testablesElement = element.addChild(name: "Testables")
-            for testable in testables {
-                testablesElement.addChild(testable.xmlElement())
+            // Xcode omits empty testables when the scheme uses test plans.
+            if !testables.isEmpty || testPlans == nil {
+                let testablesElement = element.addChild(name: "Testables")
+                for testable in testables {
+                    testablesElement.addChild(testable.xmlElement())
+                }
             }
 
-            if let commandlineArguments {
+            if let commandlineArguments, !commandlineArguments.arguments.isEmpty {
                 element.addChild(commandlineArguments.xmlElement())
             }
 
@@ -243,6 +239,13 @@ public extension XCScheme {
                 }
             }
 
+            if let testPlans {
+                let testPlansElement = element.addChild(name: "TestPlans")
+                for testPlan in testPlans {
+                    testPlansElement.addChild(testPlan.xmlElement())
+                }
+            }
+
             return element
         }
 
diff --git a/Tests/XcodeProjTests/Scheme/XCSchemeTests.swift b/Tests/XcodeProjTests/Scheme/XCSchemeTests.swift
index 160d1f78c..ddf1d0a61 100644
--- a/Tests/XcodeProjTests/Scheme/XCSchemeTests.swift
+++ b/Tests/XcodeProjTests/Scheme/XCSchemeTests.swift
@@ -299,6 +299,37 @@ final class XCSchemeIntegrationTests: XCTestCase {
         XCTAssertEqual(subject, reconstructedSubject)
     }
 
+    func test_testAction_withTestPlans_serializesLikeXcode() throws {
+        // Given
+        let subject = try XCScheme.TestAction(buildConfiguration: "Debug",
+                                              macroExpansion: nil,
+                                              testPlans: [.init(reference: "container:App.xctestplan", default: true)],
+                                              codeCoverageTargets: [buildableReferenceWithStringBluePrint()],
+                                              commandlineArguments: .init(arguments: []))
+
+        // When
+        let element = subject.xmlElement()
+
+        // Then
+        XCTAssertEqual(element.children.map(\.name), ["CodeCoverageTargets", "TestPlans"])
+    }
+
+    func test_testAction_withoutTestPlans_keepsEmptyTestables() {
+        // Given
+        let subject = XCScheme.TestAction(buildConfiguration: "Debug", macroExpansion: nil)
+
+        // When
+        let element = subject.xmlElement()
+
+        // Then
+        XCTAssertEqual(element.children.map(\.name), ["Testables"])
+    }
+
+    func test_buildAction_runPostActionsOnFailure_onlySerializedWhenEnabled() {
+        XCTAssertNil(XCScheme.BuildAction(runPostActionsOnFailure: false).xmlElement().attributes["runPostActionsOnFailure"])
+        XCTAssertEqual(XCScheme.BuildAction(runPostActionsOnFailure: true).xmlElement().attributes["runPostActionsOnFailure"], "YES")
+    }
+
     func test_scheme_remoteRunnable() throws {
         // Given / When
         let subject = try XCScheme(path: watchAppSchemePath)