run BackgroundStruct as a long-lived background process

Author: atterpac

engine/config.go

@@ -237,7 +237,12 @@ func readGitIgnore(path string) []string {
 }
 
 func (e *Engine) generateProcess() {
+	// A configured background command is started once at startup, survives
+	// reloads, and is killed on shutdown — regardless of any Type set on it.
+	if bg := e.Config.BackgroundStruct; bg.Cmd != "" {
+		_ = e.ProcessManager.AddProcess(bg.Cmd, string(process.Background), bg.ChangeDir)
+	}
 	for _, ex := range e.Config.ExecStruct {
-		e.ProcessManager.AddProcess(ex.Cmd, string(ex.Type), ex.ChangeDir)
+		_ = e.ProcessManager.AddProcess(ex.Cmd, string(ex.Type), ex.ChangeDir)
 	}
 }

engine/config_test.go

@@ -79,6 +79,21 @@ func TestVerifyExecuteRequiresAtLeastOne(t *testing.T) {
 	}
 }
 
+func TestBackgroundStructBecomesProcess(t *testing.T) {
+	eng, err := NewEngineFromConfig(Config{
+		RootPath:         ".",
+		BackgroundStruct: process.Execute{Cmd: "echo bg"},
+		ExecStruct:       []process.Execute{{Cmd: "./app", Type: process.Primary}},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	// The background command is registered ahead of the configured executes.
+	if got := eng.ProcessManager.GetExecutes(); len(got) != 2 || got[0] != "echo bg" || got[1] != "./app" {
+		t.Errorf("executes = %v, want [echo bg, ./app]", got)
+	}
+}
+
 func TestNormalizeExecutesPrefersStruct(t *testing.T) {
 	e := &Engine{Config: Config{
 		RootPath:   ".",

examples/kitchen-sink/main.go

@@ -30,6 +30,11 @@ func buildConfig(root string) engine.Config {
 		RootPath: root,
 		LogLevel: "info",
 		Debounce: 300,
+		// A standalone background service: started once, survives reloads, and is
+		// killed only on shutdown (e.g. `npm run dev`).
+		BackgroundStruct: engine.Execute{
+			Cmd: "mkdir -p artifacts && echo up >> artifacts/bgstruct.log && sleep 3600",
+		},
 		Ignore: engine.Ignore{
 			WatchedExten: []string{"*.go"},              // only react to Go changes
 			Dir:          []string{".git", "artifacts"}, // never react to our own output

examples/kitchen-sink/main_test.go

@@ -103,7 +103,7 @@ func TestKitchenSinkIntegration(t *testing.T) {
 	if !waitFor(func() bool { return lines(art("primary.log")) == 1 }) {
 		t.Fatalf("primary did not start (primary.log = %d lines)", lines(art("primary.log")))
 	}
-	for _, f := range []string{"once.log", "background.log", "blocking.log"} {
+	for _, f := range []string{"once.log", "background.log", "bgstruct.log", "blocking.log"} {
 		if !waitFor(func() bool { return lines(art(f)) >= 1 }) {
 			t.Fatalf("%s was not written on startup", f)
 		}
@@ -161,6 +161,9 @@ func TestKitchenSinkIntegration(t *testing.T) {
 	if got := lines(art("background.log")); got != 1 {
 		t.Errorf("background execute restarted (%d lines), want 1 (it should survive reloads)", got)
 	}
+	if got := lines(art("bgstruct.log")); got != 1 {
+		t.Errorf("BackgroundStruct restarted (%d lines), want 1 (it should run once and survive reloads)", got)
+	}
 }
 
 func mustMkdir(t *testing.T, path string) {