From b13f7976cc7b5aac58e66bf46b3f4c04c00ddd7d Mon Sep 17 00:00:00 2001
From: Brendan Szymanski <hello@bscubed.dev>
Date: Tue, 21 Jul 2026 20:08:39 -0400
Subject: [PATCH] Preserve user-defined test targets across Package.swift
 regeneration

---
 .../CodeGen+Scaffolding.swift                 |  7 +-
 Sources/GObjectGeneratorCore/CodeGen.swift    | 35 ++++++++++
 Sources/generator/Main.swift                  | 10 ++-
 .../ScaffoldingTests.swift                    | 64 +++++++++++++++++++
 4 files changed, 114 insertions(+), 2 deletions(-)

diff --git a/Sources/GObjectGeneratorCore/CodeGen+Scaffolding.swift b/Sources/GObjectGeneratorCore/CodeGen+Scaffolding.swift
index 4c392fc..949fa6f 100644
--- a/Sources/GObjectGeneratorCore/CodeGen+Scaffolding.swift
+++ b/Sources/GObjectGeneratorCore/CodeGen+Scaffolding.swift
@@ -256,7 +256,12 @@ extension CodeGenerator {
         \(products)        ],
             targets: [
         \(cTargets)
-        \(swiftTargets)\(smokeTarget)        ]
+        \(swiftTargets)\(smokeTarget)
+        // === USER TARGETS — preserved across generations ===
+        // BEGIN_USER_TARGETS
+
+        // END_USER_TARGETS
+        ]
         )
 
         """
diff --git a/Sources/GObjectGeneratorCore/CodeGen.swift b/Sources/GObjectGeneratorCore/CodeGen.swift
index a80543a..3a357d6 100644
--- a/Sources/GObjectGeneratorCore/CodeGen.swift
+++ b/Sources/GObjectGeneratorCore/CodeGen.swift
@@ -24,4 +24,39 @@ public struct CodeGenerator {
         }
         return files
     }
+
+    // MARK: - User target preservation
+
+    /// Preserves user-defined targets between `// BEGIN_USER_TARGETS` and
+    /// `// END_USER_TARGETS` markers when regenerating Package.swift.
+    ///
+    /// If the existing file has content between the markers, it is spliced
+    /// into the freshly generated output. If either file lacks the markers,
+    /// the generated output is returned unchanged.
+    ///
+    /// - Parameters:
+    ///   - generated: The freshly generated Package.swift content.
+    ///   - existing: The existing Package.swift on disk (if any).
+    /// - Returns: The generated content with user targets spliced in.
+    public static func preserveUserTargets(generated: String, existing: String) -> String {
+        let beginMarker = "// BEGIN_USER_TARGETS"
+        let endMarker = "// END_USER_TARGETS"
+
+        guard let genStart = generated.range(of: beginMarker),
+              let genEnd = generated.range(of: endMarker, range: genStart.upperBound..<generated.endIndex) else {
+            return generated
+        }
+
+        // Default to keeping the generated gap (blank line and indent)
+        var userContent = String(generated[genStart.upperBound..<genEnd.lowerBound])
+
+        if let exStart = existing.range(of: beginMarker),
+           let exEnd = existing.range(of: endMarker, range: exStart.upperBound..<existing.endIndex) {
+            userContent = String(existing[exStart.upperBound..<exEnd.lowerBound])
+        }
+
+        var result = generated
+        result.replaceSubrange(genStart.upperBound..<genEnd.lowerBound, with: userContent)
+        return result
+    }
 }
diff --git a/Sources/generator/Main.swift b/Sources/generator/Main.swift
index 037b8c0..7d6c32b 100644
--- a/Sources/generator/Main.swift
+++ b/Sources/generator/Main.swift
@@ -78,8 +78,16 @@ struct GeneratorCLI {
             }
 
             // Write scaffolding (Package.swift, C module maps, umbrella headers)
-            let scaffolding = CodeGenerator.generateMonorepoScaffolding(
+            var scaffolding = CodeGenerator.generateMonorepoScaffolding(
                 analysis: analysis, includeSmokeTarget: args.includeSmokeTarget)
+
+            // Preserve user-defined targets in Package.swift across generations
+            let existingPkgPath = outputRoot.appendingPathComponent("Package.swift")
+            let existingPkg = (try? String(contentsOf: existingPkgPath, encoding: .utf8)) ?? ""
+            if let pkgContent = scaffolding["Package.swift"] {
+                scaffolding["Package.swift"] = CodeGenerator.preserveUserTargets(
+                    generated: pkgContent, existing: existingPkg)
+            }
             for (relativePath, content) in scaffolding.sorted(by: { $0.key < $1.key }) {
                 let fileURL = outputRoot.appendingPathComponent(relativePath)
                 try FileManager.default.createDirectory(at: fileURL.deletingLastPathComponent(), withIntermediateDirectories: true)
diff --git a/Tests/GObjectGeneratorCoreTests/ScaffoldingTests.swift b/Tests/GObjectGeneratorCoreTests/ScaffoldingTests.swift
index 9b573df..1504a67 100644
--- a/Tests/GObjectGeneratorCoreTests/ScaffoldingTests.swift
+++ b/Tests/GObjectGeneratorCoreTests/ScaffoldingTests.swift
@@ -96,3 +96,67 @@ func testPackageScaffoldingAdw() {
     #expect(scaffolding["Sources/CAdw/module.modulemap"]?.contains("link \"adwaita-1\"") == true)
     #expect(scaffolding["Sources/CAdw/CAdw.h"]?.contains("#include <adwaita.h>") == true)
 }
+
+// MARK: - User target preservation
+
+@Test("generateMonorepoScaffolding includes user targets marker block")
+func testMonorepoPackageHasUserTargetMarkers() {
+    // Build minimal MultiPackageAnalysis with one module
+    let repo = Repository(
+        namespaces: [Namespace(name: "Gtk", version: "4.0",
+            cSharedLibrary: "libgtk-4.so.1", cIdentifierPrefix: "Gtk")]
+    )
+    let analysis = MultiPackageAnalysis(
+        repositories: ["Gtk": repo],
+        directDependencies: ["Gtk": []],
+        transitiveDependencies: ["Gtk": []],
+        implicitImports: ["Gtk": []],
+        packageConfigs: [:]
+    )
+    let scaffolding = CodeGenerator.generateMonorepoScaffolding(analysis: analysis)
+    let pkg = scaffolding["Package.swift"] ?? ""
+    #expect(pkg.contains("// BEGIN_USER_TARGETS"))
+    #expect(pkg.contains("// END_USER_TARGETS"))
+}
+
+@Test("preserveUserTargets splices user block from existing into generated")
+func testPreserveUserTargets() {
+    let existing = """
+    targets: [
+        .systemLibrary(name: "CGLib"),
+        // BEGIN_USER_TARGETS
+        .testTarget(name: "MyTests", dependencies: ["GLib"]),
+        // END_USER_TARGETS
+    ]
+    """
+
+    let generated = """
+    targets: [
+        .systemLibrary(name: "CGLib"),
+        // BEGIN_USER_TARGETS
+
+        // END_USER_TARGETS
+    ]
+    """
+    let result = CodeGenerator.preserveUserTargets(generated: generated, existing: existing)
+    #expect(result.contains("MyTests"))
+    #expect(result != generated, "Result should differ from generated since existing has content")
+    #expect(result.contains("// BEGIN_USER_TARGETS"))
+    #expect(result.contains("// END_USER_TARGETS"))
+    #expect(result.contains(".testTarget(name:"))
+}
+
+@Test("preserveUserTargets returns generated unchanged when existing has no markers")
+func testPreserveUserTargetsFirstGeneration() {
+    let generated = """
+    targets: [
+        .systemLibrary(name: "CGLib"),
+        // BEGIN_USER_TARGETS
+
+        // END_USER_TARGETS
+    ]
+    """
+
+    let result = CodeGenerator.preserveUserTargets(generated: generated, existing: "")
+    #expect(result == generated)
+}