migrate to v2 hacks: infer process names when possible (#2837)

* `migrate-to-v2` hacks: add process to services if none are specified
* `migrate-to-v2` hacks: infer process name when specified by services

Author: Allison Pierson

internal/command/migrate_to_v2/hacks.go

@@ -0,0 +1,60 @@
+package migrate_to_v2
+
+import (
+	"context"
+
+	"github.com/samber/lo"
+	"github.com/superfly/flyctl/api"
+)
+
+// This all *should* work, based on the assumption that the existing app was validated and is running.
+// Essentially, we shouldn't make things up here, but extrapolate the *only* possible outcome.
+
+func (m *v2PlatformMigrator) applyHacks(ctx context.Context) {
+
+	m.hackAddProcessToServices(ctx)
+	m.hackInferProcessName(ctx)
+}
+
+// If there is only one process to the app, we can assume that services are all tied to that one process
+// unless they specify another process name
+func (m *v2PlatformMigrator) hackAddProcessToServices(ctx context.Context) {
+	appProcesses := m.appConfig.ProcessNames()
+
+	if len(appProcesses) != 1 {
+		// Apps typically aren't hosting services on multiple process groups, so we can't really
+		// make a good prediction here.
+		return
+	}
+
+	for idx := range m.appConfig.Services {
+		if len(m.appConfig.Services[idx].Processes) == 0 {
+			m.appConfig.Services[idx].Processes = appProcesses
+		}
+	}
+	if m.appConfig.HTTPService != nil && len(m.appConfig.HTTPService.Processes) == 0 {
+		m.appConfig.HTTPService.Processes = appProcesses
+	}
+}
+
+func (m *v2PlatformMigrator) hackInferProcessName(ctx context.Context) {
+
+	existingNames := m.appConfig.ProcessNames()
+	if len(existingNames) > 1 || existingNames[0] != api.MachineProcessGroupApp {
+		return
+	}
+
+	// There's a single process, and it's unnamed. See if we can infer its name from services
+	var listedNames []string
+	for _, service := range m.appConfig.AllServices() {
+		listedNames = append(listedNames, service.Processes...)
+	}
+	listedNames = lo.Uniq(listedNames)
+
+	if len(listedNames) == 1 {
+		// There's a single name listed, so we can assume that that's the only process.
+		m.appConfig.Processes = map[string]string{
+			listedNames[0]: "", // an empty cmd will inherit the CMD from the Dockerfile, or from Experimental.Cmd
+		}
+	}
+}

internal/command/migrate_to_v2/migrate_to_v2.go

@@ -341,6 +341,9 @@ func NewV2PlatformMigrator(ctx context.Context, appName string) (V2PlatformMigra
 		}
 		migrator.pgConsulUrl = consul.ConsulURL
 	}
+
+	migrator.applyHacks(ctx)
+
 	err = migrator.validate(ctx)
 	if err != nil {
 		return nil, err