Add depends_on field for core service ordering

* Adds depends_on fields to compose YAML
* Updates parsing code to copy across depends_on field to
openfaas service from compose service definition
* Adds algorithm and unit tests for finding order
* Applies order to up.go command
* Makes unit testing on MacOS possible through build directives

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/depends_on_test.go

@@ -0,0 +1,224 @@
+package pkg
+
+import (
+	"log"
+	"testing"
+)
+
+func Test_buildInstallOrder_ARequiresB(t *testing.T) {
+	svcs := []Service{
+		{
+			Name:      "A",
+			DependsOn: []string{"B"},
+		},
+		{
+			Name:      "B",
+			DependsOn: []string{},
+		},
+	}
+
+	order := buildInstallOrder(svcs)
+
+	if len(order) < len(svcs) {
+		t.Fatalf("length of order too short: %d", len(order))
+	}
+
+	got := order[0]
+	want := "B"
+	if got != want {
+		t.Fatalf("%s should be last to be installed, but was: %s", want, got)
+	}
+}
+
+func Test_buildInstallOrder_ARequiresBAndC(t *testing.T) {
+	svcs := []Service{
+		{
+			Name:      "A",
+			DependsOn: []string{"B", "C"},
+		},
+		{
+			Name:      "B",
+			DependsOn: []string{},
+		},
+		{
+			Name:      "C",
+			DependsOn: []string{},
+		},
+	}
+
+	order := buildInstallOrder(svcs)
+
+	if len(order) < len(svcs) {
+		t.Fatalf("length of order too short: %d", len(order))
+	}
+
+	a := indexStr(order, "a")
+	b := indexStr(order, "b")
+	c := indexStr(order, "c")
+
+	if a > b {
+		t.Fatalf("a should be after dependencies")
+	}
+	if a > c {
+		t.Fatalf("a should be after dependencies")
+	}
+
+}
+
+func Test_buildInstallOrder_ARequiresBRequiresC(t *testing.T) {
+	svcs := []Service{
+		{
+			Name:      "A",
+			DependsOn: []string{"B"},
+		},
+		{
+			Name:      "B",
+			DependsOn: []string{"C"},
+		},
+		{
+			Name:      "C",
+			DependsOn: []string{},
+		},
+	}
+
+	order := buildInstallOrder(svcs)
+
+	if len(order) < len(svcs) {
+		t.Fatalf("length of order too short: %d", len(order))
+	}
+
+	got := order[0]
+	want := "C"
+	if got != want {
+		t.Fatalf("%s should be last to be installed, but was: %s", want, got)
+	}
+	got = order[1]
+	want = "B"
+	if got != want {
+		t.Fatalf("%s should be last to be installed, but was: %s", want, got)
+	}
+	got = order[2]
+	want = "A"
+	if got != want {
+		t.Fatalf("%s should be last to be installed, but was: %s", want, got)
+	}
+}
+
+func Test_buildInstallOrderCircularARequiresBRequiresA(t *testing.T) {
+	svcs := []Service{
+		{
+			Name:      "A",
+			DependsOn: []string{"B"},
+		},
+		{
+			Name:      "B",
+			DependsOn: []string{"A"},
+		},
+	}
+
+	defer func() { recover() }()
+
+	buildInstallOrder(svcs)
+
+	t.Fatalf("did not panic as expected")
+}
+
+func Test_buildInstallOrderComposeFile(t *testing.T) {
+	// svcs := []Service{}
+	file, err := LoadComposeFileWithArch("../", "docker-compose.yaml", func() (string, string) {
+		return "x86_64", "Linux"
+	})
+
+	if err != nil {
+		t.Fatalf("unable to load compose file: %s", err)
+	}
+
+	svcs, err := ParseCompose(file)
+	if err != nil {
+		t.Fatalf("unable to parse compose file: %s", err)
+	}
+
+	for _, s := range svcs {
+		log.Printf("Service: %s\n", s.Name)
+		for _, d := range s.DependsOn {
+			log.Printf("Link: %s => %s\n", s.Name, d)
+		}
+	}
+
+	order := buildInstallOrder(svcs)
+
+	if len(order) < len(svcs) {
+		t.Fatalf("length of order too short: %d", len(order))
+	}
+
+	queueWorker := indexStr(order, "queue-worker")
+	nats := indexStr(order, "nats")
+	gateway := indexStr(order, "gateway")
+	prometheus := indexStr(order, "prometheus")
+
+	if prometheus > gateway {
+		t.Fatalf("Prometheus order was after gateway, and should be before")
+	}
+	if nats > gateway {
+		t.Fatalf("NATS order was after gateway, and should be before")
+	}
+	if nats > queueWorker {
+		t.Fatalf("NATS order was after queue-worker, and should be before")
+	}
+}
+
+func Test_buildInstallOrderOpenFaaS(t *testing.T) {
+	svcs := []Service{
+		{
+			Name:      "queue-worker",
+			DependsOn: []string{"nats"},
+		},
+		{
+			Name:      "prometheus",
+			DependsOn: []string{},
+		},
+		{
+			Name:      "gateway",
+			DependsOn: []string{"prometheus", "nats", "basic-auth-plugin"},
+		},
+		{
+			Name:      "basic-auth-plugin",
+			DependsOn: []string{},
+		},
+		{
+			Name:      "nats",
+			DependsOn: []string{},
+		},
+	}
+
+	order := buildInstallOrder(svcs)
+
+	if len(order) < len(svcs) {
+		t.Fatalf("length of order too short: %d", len(order))
+	}
+
+	queueWorker := indexStr(order, "queue-worker")
+	nats := indexStr(order, "nats")
+	gateway := indexStr(order, "gateway")
+	prometheus := indexStr(order, "prometheus")
+
+	if prometheus > gateway {
+		t.Fatalf("Prometheus order was after gateway, and should be before")
+	}
+	if nats > gateway {
+		t.Fatalf("NATS order was after gateway, and should be before")
+	}
+	if nats > queueWorker {
+		t.Fatalf("NATS order was after queue-worker, and should be before")
+	}
+}
+
+func indexStr(st []string, t string) int {
+	for n, s := range st {
+		if s == t {
+			return n
+		}
+
+	}
+	return -1
+}