api: accepted require_billing_address in /v1/checkout

This also adds test coverage for Checkout.

Fixes #252

api/api.go

@@ -189,9 +189,10 @@ func (h *Handler) serveCheckout(w http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 	link, err := h.c.Checkout(r.Context(), cr.Org, cr.SuccessURL, &control.CheckoutParams{
-		TrialDays: cr.TrialDays,
-		Features:  fs,
-		CancelURL: cr.CancelURL,
+		TrialDays:             cr.TrialDays,
+		Features:              fs,
+		CancelURL:             cr.CancelURL,
+		RequireBillingAddress: cr.RequireBillingAddress,
 	})
 	if err != nil {
 		return err

api/apitypes/apitypes.go

@@ -47,11 +47,12 @@ type OrgInfo struct {
 }
 
 type CheckoutRequest struct {
-	Org        string   `json:"org"`
-	TrialDays  int      `json:"trial_days"`
-	Features   []string `json:"features"`
-	SuccessURL string   `json:"success_url"`
-	CancelURL  string   `json:"cancel_url"`
+	Org                   string   `json:"org"`
+	TrialDays             int      `json:"trial_days"`
+	Features              []string `json:"features"`
+	SuccessURL            string   `json:"success_url"`
+	CancelURL             string   `json:"cancel_url"`
+	RequireBillingAddress bool     `json:"require_billing_address"`
 }
 
 type ScheduleRequest struct {

client/tier/client.go

@@ -250,11 +250,12 @@ func (c *Client) Checkout(ctx context.Context, org string, successURL string, p
 		p = &CheckoutParams{}
 	}
 	r := &apitypes.CheckoutRequest{
-		Org:        org,
-		SuccessURL: successURL,
-		CancelURL:  p.CancelURL,
-		TrialDays:  p.TrialDays,
-		Features:   p.Features,
+		Org:                   org,
+		SuccessURL:            successURL,
+		CancelURL:             p.CancelURL,
+		TrialDays:             p.TrialDays,
+		Features:              p.Features,
+		RequireBillingAddress: p.RequireBillingAddress,
 	}
 	return fetchOK[*apitypes.CheckoutResponse, *apitypes.Error](ctx, c, "POST", "/v1/checkout", r)
 }
@@ -263,9 +264,10 @@ type Phase = apitypes.Phase
 type OrgInfo = apitypes.OrgInfo
 
 type CheckoutParams struct {
-	TrialDays int
-	Features  []string
-	CancelURL string
+	TrialDays             int
+	Features              []string
+	CancelURL             string
+	RequireBillingAddress bool
 }
 
 type ScheduleParams struct {

cmd/tier/tier.go

@@ -277,6 +277,7 @@ func runTier(cmd string, args []string) (err error) {
 		cancel := fs.Bool("cancel", false, "cancels the subscription")
 		successURL := fs.String("checkout", "", "subscribe via Stripe checkout")
 		cancelURL := fs.String("cancel_url", "", "sets the cancel URL for use with -checkout")
+		requireBillingAddress := fs.Bool("require_billing_address", false, "require billing address for use with --checkout")
 		if err := fs.Parse(args); err != nil {
 			return err
 		}
@@ -301,9 +302,10 @@ func runTier(cmd string, args []string) (err error) {
 		useCheckout := *successURL != ""
 		if useCheckout {
 			cr, err := tc().Checkout(ctx, org, *successURL, &tier.CheckoutParams{
-				TrialDays: *trial,
-				Features:  refs,
-				CancelURL: *cancelURL,
+				TrialDays:             *trial,
+				Features:              refs,
+				CancelURL:             *cancelURL,
+				RequireBillingAddress: *requireBillingAddress,
 			})
 			if err != nil {
 				return err

control/schedule.go

@@ -419,9 +419,10 @@ func addPhases(ctx context.Context, c *Client, f *stripe.Form, update bool, name
 }
 
 type CheckoutParams struct {
-	TrialDays int
-	Features  []Feature
-	CancelURL string
+	TrialDays             int
+	Features              []Feature
+	CancelURL             string
+	RequireBillingAddress bool
 }
 
 func (c *Client) Checkout(ctx context.Context, org string, successURL string, p *CheckoutParams) (link string, err error) {
@@ -446,6 +447,9 @@ func (c *Client) Checkout(ctx context.Context, org string, successURL string, p
 	if p.CancelURL != "" {
 		f.Set("cancel_url", p.CancelURL)
 	}
+	if p.RequireBillingAddress {
+		f.Set("billing_address_collection", "required")
+	}
 	if len(p.Features) == 0 {
 		f.Set("mode", "setup")
 		// TODO: support other payment methods:

control/schedule_test.go

@@ -2,13 +2,16 @@ package control
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
 	"os"
 	"regexp"
+	"strconv"
+	"sync"
 	"testing"
 	"time"
 
@@ -21,6 +24,7 @@ import (
 	"tier.run/refs"
 	"tier.run/stripe"
 	"tier.run/stripe/stroke"
+	"tier.run/values"
 )
 
 var (
@@ -695,6 +699,95 @@ func TestLookupPhases(t *testing.T) {
 	diff.Test(t, t.Errorf, got, want, ignoreProviderIDs)
 }
 
+func TestCheckoutRequiredAddress(t *testing.T) {
+	type G struct {
+		successURL string
+		cancelURL  string
+		bac        string // billing_address_collection
+		trialDays  string
+	}
+
+	var mu sync.Mutex
+	var got []G
+	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case wants(r, "GET", "/v1/customers"):
+			jsonEncode(t, w, msa{
+				"data": []msa{
+					{
+						"metadata": msa{
+							"tier.org": "org:demo",
+						},
+					},
+				},
+			})
+		case wants(r, "POST", "/v1/checkout/sessions"):
+			mu.Lock()
+			got = append(got, G{
+				successURL: r.FormValue("success_url"),
+				cancelURL:  r.FormValue("cancel_url"),
+				bac:        r.FormValue("billing_address_collection"),
+				trialDays:  r.FormValue("subscription_data[trial_period_days]"),
+			})
+			mu.Unlock()
+			jsonEncode(t, w, msa{
+				"URL": "http://co.com/123",
+			})
+		default:
+			t.Errorf("UNEXPECTED: %s %s", r.Method, r.URL.Path)
+		}
+	})
+
+	s := httptest.NewServer(h)
+	t.Cleanup(s.Close)
+
+	cc := &Client{
+		Logf: t.Logf,
+		Stripe: &stripe.Client{
+			BaseURL: s.URL,
+		},
+	}
+
+	TF := []bool{true, false}
+	for _, withAddress := range TF {
+		for _, withFeatures := range TF {
+			for _, withCancel := range TF {
+				for _, withTrial := range TF {
+					got = nil
+
+					var (
+						bac       = values.ReturnIf(withAddress, "required")
+						cancelURL = values.ReturnIf(withCancel, "https://c.com")
+						features  = values.ReturnIf(withFeatures, []Feature{{}})
+						trialDays = values.ReturnIf(withTrial, 14)
+					)
+
+					link, err := cc.Checkout(context.Background(), "org:demo", "http://s.com", &CheckoutParams{
+						Features:              features,
+						RequireBillingAddress: withAddress,
+						CancelURL:             cancelURL,
+						TrialDays:             trialDays,
+					})
+					if err != nil {
+						t.Fatal(err)
+					}
+
+					if want := "http://co.com/123"; link != want {
+						t.Errorf("link = %q; want %q", link, want)
+					}
+
+					diff.Test(t, t.Errorf, got, []G{{
+						successURL: "http://s.com",
+						cancelURL:  cancelURL,
+						bac:        bac,
+						trialDays:  values.ReturnIf(withTrial && withFeatures, strconv.Itoa(trialDays)),
+					}})
+				}
+			}
+		}
+	}
+}
+
 func TestLookupPhasesNoSchedule(t *testing.T) {
 	// TODO(bmizerany): This tests assumptions, but we need an integration
 	// test provin fields "like" trial actually fall off / go to zero when
@@ -1124,3 +1217,12 @@ func writeHuJSON(w io.Writer, s string, args ...any) {
 		panic(err)
 	}
 }
+
+type msa map[string]any
+
+func jsonEncode(t *testing.T, w io.Writer, v any) {
+	t.Helper()
+	if err := json.NewEncoder(w).Encode(v); err != nil {
+		t.Error(err)
+	}
+}

values/values.go

@@ -21,6 +21,23 @@ func MaybeSet[T comparable](v *T, a T) {
 	*v = Coalesce(*v, a)
 }
 
+// ReturnIf retuns a if cond is true; otherwise the zero value of T is
+// returned.
+func ReturnIf[T any](cond bool, a T) T {
+	if cond {
+		return a
+	}
+	var zero T
+	return zero
+}
+
+// SetIf sets v to a if cond is true
+func SetIf[T any](v *T, cond bool, a T) {
+	if cond {
+		*v = a
+	}
+}
+
 type Collection[K comparable, V any] map[K][]V
 
 func (c *Collection[K, V]) Add(key K, v V) {