From 5450c861d4355b7696ad5143e0019c2b41f2d320 Mon Sep 17 00:00:00 2001
From: Fredrik Ahlgren <fredrik@sourceful-labs.com>
Date: Mon, 7 Sep 2026 12:42:22 +0200
Subject: [PATCH] fix(updater): split compose owner handling by platform

Signed-off-by: Fredrik Ahlgren <fredrik@sourceful-labs.com>
---
 .changeset/calm-windows-owner.md       |  5 +++++
 go/cmd/ftw-updater/file_owner_other.go |  9 +++++++++
 go/cmd/ftw-updater/file_owner_unix.go  | 16 ++++++++++++++++
 go/cmd/ftw-updater/retire_python.go    |  7 ++-----
 4 files changed, 32 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/calm-windows-owner.md
 create mode 100644 go/cmd/ftw-updater/file_owner_other.go
 create mode 100644 go/cmd/ftw-updater/file_owner_unix.go

diff --git a/.changeset/calm-windows-owner.md b/.changeset/calm-windows-owner.md
new file mode 100644
index 00000000..0815e049
--- /dev/null
+++ b/.changeset/calm-windows-owner.md
@@ -0,0 +1,5 @@
+---
+"ftw": patch
+---
+
+Build the updater on Windows while preserving Compose file ownership on Unix.
diff --git a/go/cmd/ftw-updater/file_owner_other.go b/go/cmd/ftw-updater/file_owner_other.go
new file mode 100644
index 00000000..02977b44
--- /dev/null
+++ b/go/cmd/ftw-updater/file_owner_other.go
@@ -0,0 +1,9 @@
+//go:build !unix
+
+package main
+
+import "os"
+
+// Non-Unix systems have no portable numeric owner to copy. The staged file
+// keeps the owner and access rules assigned by the platform.
+func preserveFileOwner(_ *os.File, _ os.FileInfo) error { return nil }
diff --git a/go/cmd/ftw-updater/file_owner_unix.go b/go/cmd/ftw-updater/file_owner_unix.go
new file mode 100644
index 00000000..9e20d141
--- /dev/null
+++ b/go/cmd/ftw-updater/file_owner_unix.go
@@ -0,0 +1,16 @@
+//go:build unix
+
+package main
+
+import (
+	"os"
+	"syscall"
+)
+
+func preserveFileOwner(file *os.File, info os.FileInfo) error {
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	if !ok {
+		return nil
+	}
+	return file.Chown(int(stat.Uid), int(stat.Gid))
+}
diff --git a/go/cmd/ftw-updater/retire_python.go b/go/cmd/ftw-updater/retire_python.go
index e045d4df..0ba2aa1d 100644
--- a/go/cmd/ftw-updater/retire_python.go
+++ b/go/cmd/ftw-updater/retire_python.go
@@ -10,7 +10,6 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
-	"syscall"
 	"time"
 
 	"gopkg.in/yaml.v3"
@@ -327,10 +326,8 @@ func replaceRetiredCompose(path string, data []byte) error {
 	}
 	defer os.Remove(f.Name())
 	defer f.Close()
-	if stat, ok := st.Sys().(*syscall.Stat_t); ok {
-		if err = f.Chown(int(stat.Uid), int(stat.Gid)); err != nil {
-			return err
-		}
+	if err = preserveFileOwner(f, st); err != nil {
+		return err
 	}
 	if err = f.Chmod(st.Mode().Perm()); err != nil {
 		return err