launch: nudge users to fly deploy if they can see app with the cu…

…rrent app name (#3622)

* `launch`: prompt users to deploy instead if they can see the named app

* `launch`: remove requirement on copied config for deploy prompt

internal/command/launch/plan_builder.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"os"
 	"path/filepath"
 	"reflect"
 	"regexp"
@@ -161,6 +162,12 @@ func buildManifest(ctx context.Context, recoverableErrors *recoverableErrorBuild
 		}
 	}
 
+	// If the user can see an app with the same name as what they're about to launch,
+	// they *probably* want to deploy to that app instead.
+	if err := nudgeTowardsDeploy(ctx, appName); err != nil {
+		return nil, nil, err
+	}
+
 	compute, computeExplanation, err := determineCompute(ctx, appConfig, srcInfo)
 	if err != nil {
 		if err := recoverableErrors.tryRecover(err); err != nil {
@@ -249,6 +256,40 @@ func buildManifest(ctx context.Context, recoverableErrors *recoverableErrorBuild
 	}, buildCache, nil
 }
 
+// Check to see if they own the named app, and if so, prompt them to try deploying instead.
+func nudgeTowardsDeploy(ctx context.Context, appName string) error {
+
+	client := flyutil.ClientFromContext(ctx)
+	io := iostreams.FromContext(ctx)
+
+	if flag.GetYes(ctx) {
+		return nil
+	}
+
+	if _, err := client.GetApp(ctx, appName); err != nil {
+		// The user can't see the app. Let them proceed.
+		return nil
+	}
+
+	// The user can see the app. Prompt them to deploy.
+	fmt.Fprintf(io.Out, "App '%s' already exists. You can deploy to it with `fly deploy`.\n", appName)
+
+	switch confirmed, err := prompt.Confirm(ctx, "Continue launching a new app? "); {
+	case err == nil:
+		if !confirmed {
+			// We've redirected the user to use 'fly deploy'
+			// Exit directly with code 0 so this isn't flagged as a failed launch
+			os.Exit(0)
+		}
+	case prompt.IsNonInteractive(err):
+		// Should be impossible - we're only called if recoverableErrors.canEnterUi is true
+		return nil
+	default:
+		return err
+	}
+	return nil
+}
+
 func stateFromManifest(ctx context.Context, m LaunchManifest, optionalCache *planBuildCache, recoverableErrors *recoverableErrorBuilder) (*launchState, error) {
 	var (
 		io     = iostreams.FromContext(ctx)