Add ctx fork for concurrent access (#13)

client.go

@@ -119,6 +119,35 @@ func (c *Client) Reset() *Client {
 	return c
 }
 
+// Fork checks ctx for an existing clone of this Client.
+// If one is found, it is returned together with unmodified context.
+// Otherwise, a clone of Client is created and put into a new derived context,
+// then both new context and cloned Client are returned.
+//
+// This method enables context-driven concurrent access to shared base Client.
+func (c *Client) Fork(ctx context.Context) (context.Context, *Client) {
+	// Pointer to current Client is used as context key
+	// to enable multiple different clients in sam context.
+	if fc, ok := ctx.Value(c).(*Client); ok {
+		return ctx, fc
+	}
+
+	// Making a copy of this Client.
+	cc := *c
+	fc := &cc
+	fc.JSONComparer = c.JSONComparer
+
+	fc.Reset().WithContext(ctx)
+
+	if c.JSONComparer.Vars != nil {
+		ctx, fc.JSONComparer.Vars = c.JSONComparer.Vars.Fork(ctx)
+	}
+
+	ctx = context.WithValue(ctx, c, fc)
+
+	return ctx, fc
+}
+
 // FollowRedirects enables automatic following of Location header.
 func (c *Client) FollowRedirects() *Client {
 	c.followRedirects = true

client_test.go

@@ -6,8 +6,10 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"sync"
 	"sync/atomic"
 	"testing"
+	"time"
 
 	"github.com/bool64/httpmock"
 	"github.com/bool64/shared"
@@ -194,3 +196,58 @@ func TestNewClient_formData(t *testing.T) {
 	assert.EqualError(t, c.ExpectResponseBody([]byte(`{"foo":"bar}"`)),
 		"unexpected body, expected: \"{\\\"foo\\\":\\\"bar}\\\"\", received: \"{\\\"bar\\\":\\\"foo\\\"}\"")
 }
+
+func TestClient_Fork(t *testing.T) {
+	c1 := httpmock.NewClient("https://one")
+	c2 := httpmock.NewClient("https://two")
+
+	c1.JSONComparer.Vars = &shared.Vars{}
+	c1.JSONComparer.Vars.Set("foo", 123)
+
+	wg := sync.WaitGroup{}
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+
+		go func() {
+			defer wg.Done()
+
+			ctx := context.Background()
+
+			ctx, fc1 := c1.Fork(ctx)
+			assert.NotNil(t, fc1)
+			fc1.WithMethod(http.MethodGet)
+
+			fc1.JSONComparer.Vars.Set("bar", 345)
+			foo, ok := fc1.JSONComparer.Vars.Get("foo")
+			assert.True(t, ok)
+			assert.Equal(t, 123, foo)
+
+			ctx, fc2 := c2.Fork(ctx)
+			assert.NotNil(t, fc2)
+			fc2.WithMethod(http.MethodPost)
+
+			ctx1, fc1a := c1.Fork(ctx)
+			assert.Equal(t, fc1a, fc1)
+			assert.True(t, c1 != fc1)
+			assert.Equal(t, ctx, ctx1)
+
+			ctx2, fc2a := c2.Fork(ctx)
+			assert.Equal(t, fc2a, fc2)
+			assert.True(t, c2 != fc2)
+			assert.Equal(t, ctx, ctx2)
+		}()
+	}
+
+	done := make(chan struct{})
+
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+
+	select {
+	case <-time.After(10 * time.Second):
+		assert.Fail(t, "could not wait for goroutines to finish")
+	case <-done:
+	}
+}

go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/bool64/dev v0.2.27
 	github.com/bool64/shared v0.1.5
 	github.com/stretchr/testify v1.8.2
-	github.com/swaggest/assertjson v1.8.0
+	github.com/swaggest/assertjson v1.8.1
 )
 
 require (

go.sum

@@ -33,8 +33,8 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
 github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-github.com/swaggest/assertjson v1.8.0 h1:XSg4p6iOZMjtpV2tW2SXfD1GsOOTsWcm+sOADODu/DU=
-github.com/swaggest/assertjson v1.8.0/go.mod h1:/8kNRmDZAZfavS5VeWYtCimLGebn0Ak1/iErFUi+DEM=
+github.com/swaggest/assertjson v1.8.1 h1:Be2EHY9S2qwKWV+xWZB747Cd7Y79YK6JLdeyrgFvyMo=
+github.com/swaggest/assertjson v1.8.1/go.mod h1:/8kNRmDZAZfavS5VeWYtCimLGebn0Ak1/iErFUi+DEM=
 github.com/yosuke-furukawa/json5 v0.1.2-0.20201207051438-cf7bb3f354ff h1:7YqG491bE4vstXRz1lD38rbSgbXnirvROz1lZiOnPO8=
 github.com/yosuke-furukawa/json5 v0.1.2-0.20201207051438-cf7bb3f354ff/go.mod h1:sw49aWDqNdRJ6DYUtIQiaA3xyj2IL9tjeNYmX2ixwcU=
 github.com/yudai/gojsondiff v1.0.0 h1:27cbfqXLVEJ1o8I6v3y9lg8Ydm53EKqHXAOMxEGlCOA=