From 46a2f52ca6d1746494e44e7e45bcbb660e3555a4 Mon Sep 17 00:00:00 2001
From: Owen <ojracc@gmail.com>
Date: Wed, 24 Apr 2019 11:31:19 -0400
Subject: [PATCH 1/2] Return errors from JSON encode/decode

I found two JSON errors being shadowed; the one in amazon/validator.go
is being hidden by errors.New(responseError.Message) -- which should be
an empty string if there's a JSON error. So, it wouldn't report success,
but this gives the caller better information on what failed.

The second is in appstore/validator.go, which was ignoring encode errors
before POSTing a verify request.
---
 amazon/validator.go   | 3 +++
 appstore/validator.go | 4 +++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/amazon/validator.go b/amazon/validator.go
index 46a29c1..ea32c8f 100644
--- a/amazon/validator.go
+++ b/amazon/validator.go
@@ -102,6 +102,9 @@ func (c *Client) Verify(ctx context.Context, userID string, receiptID string) (I
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		responseError := IAPResponseError{}
 		err = json.NewDecoder(resp.Body).Decode(&responseError)
+		if err != nil {
+			return result, err
+		}
 		return result, errors.New(responseError.Message)
 	}
 
diff --git a/appstore/validator.go b/appstore/validator.go
index 1a0ff80..4786f01 100644
--- a/appstore/validator.go
+++ b/appstore/validator.go
@@ -98,7 +98,9 @@ func NewWithClient(client *http.Client) *Client {
 // Verify sends receipts and gets validation result
 func (c *Client) Verify(ctx context.Context, reqBody IAPRequest, result interface{}) error {
 	b := new(bytes.Buffer)
-	json.NewEncoder(b).Encode(reqBody)
+	if err := json.NewEncoder(b).Encode(reqBody); err != nil {
+		return err
+	}
 
 	req, err := http.NewRequest("POST", c.ProductionURL, b)
 	if err != nil {

From 92d56725f73ca25135dae914daaf17dabe074eeb Mon Sep 17 00:00:00 2001
From: Owen <ojracc@gmail.com>
Date: Wed, 24 Apr 2019 11:36:47 -0400
Subject: [PATCH 2/2] Unwrap error in Amazon validator

In amazon/validator.go, an error was being wrapped by fmt.Errorf("%v",
err). That discards any type information about the returned error;
returning err lets the callers inspect the exact error returned by the
HTTP client.

The test had to change to do similar inspection.
---
 amazon/validator.go      |  2 +-
 amazon/validator_test.go | 13 ++++++++++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/amazon/validator.go b/amazon/validator.go
index ea32c8f..0a3eb68 100644
--- a/amazon/validator.go
+++ b/amazon/validator.go
@@ -95,7 +95,7 @@ func (c *Client) Verify(ctx context.Context, userID string, receiptID string) (I
 
 	resp, err := c.httpCli.Do(req)
 	if err != nil {
-		return result, fmt.Errorf("%v", err)
+		return result, err
 	}
 	defer resp.Body.Close()
 
diff --git a/amazon/validator_test.go b/amazon/validator_test.go
index 4bc9629..1cc80cb 100644
--- a/amazon/validator_test.go
+++ b/amazon/validator_test.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"reflect"
 	"testing"
@@ -143,11 +144,17 @@ func TestVerifyTimeout(t *testing.T) {
 	server, client := testTools(100, "timeout response")
 	defer server.Close()
 
-	expected := errors.New("")
 	ctx := context.Background()
 	_, actual := client.Verify(ctx, "timeout", "timeout")
-	if !reflect.DeepEqual(reflect.TypeOf(actual), reflect.TypeOf(expected)) {
-		t.Errorf("got %v\nwant %v", actual, expected)
+
+	// Actual should be a "request canceled" *url.Error
+	urlErr, ok := actual.(*url.Error)
+	if !ok {
+		t.Errorf("Expected *url.Error, got %T", actual)
+	}
+
+	if !urlErr.Timeout() {
+		t.Errorf("got %v\nwant timeout", actual)
 	}
 }