refactor: continue to simplify engine/netx (#769)

The objective of this diff is to simplify the code inside engine/netx
while moving more bits of code inside netxlite.

See https://github.com/ooni/probe/issues/2121

internal/engine/netx/dialer/bytecounter.go

@@ -1,5 +0,0 @@
-package dialer
-
-import "github.com/ooni/probe-cli/v3/internal/bytecounter"
-
-type byteCounterDialer = bytecounter.ContextAwareDialer

internal/engine/netx/dialer/dialer.go

@@ -1,8 +1,12 @@
+// Package dialer allows you to create a net.Dialer-compatible
+// DialContext-enabled dialer with error wrapping, optional logging,
+// optional network-events saving, and optional proxying.
 package dialer
 
 import (
 	"net/url"
 
+	"github.com/ooni/probe-cli/v3/internal/bytecounter"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
 	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
@@ -63,9 +67,9 @@ func New(config *Config, resolver model.Resolver) model.Dialer {
 		Resolver: resolver,
 		Dialer:   d,
 	}
-	d = &proxyDialer{ProxyURL: config.ProxyURL, Dialer: d}
+	d = &netxlite.MaybeProxyDialer{ProxyURL: config.ProxyURL, Dialer: d}
 	if config.ContextByteCounting {
-		d = &byteCounterDialer{Dialer: d}
+		d = &bytecounter.ContextAwareDialer{Dialer: d}
 	}
 	return d
 }

internal/engine/netx/dialer/dialer_test.go

@@ -1,10 +1,12 @@
 package dialer
 
 import (
+	"net/http"
 	"net/url"
 	"testing"
 
 	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/bytecounter"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
@@ -18,11 +20,11 @@ func TestNewCreatesTheExpectedChain(t *testing.T) {
 		ProxyURL:            &url.URL{},
 		ReadWriteSaver:      saver,
 	}, netxlite.DefaultResolver)
-	bcd, ok := dlr.(*byteCounterDialer)
+	bcd, ok := dlr.(*bytecounter.ContextAwareDialer)
 	if !ok {
 		t.Fatal("not a byteCounterDialer")
 	}
-	pd, ok := bcd.Dialer.(*proxyDialer)
+	pd, ok := bcd.Dialer.(*netxlite.MaybeProxyDialer)
 	if !ok {
 		t.Fatal("not a proxyDialer")
 	}
@@ -51,3 +53,18 @@ func TestNewCreatesTheExpectedChain(t *testing.T) {
 		t.Fatal("not a DialerSystem")
 	}
 }
+
+func TestDialerNewSuccess(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
+	log.SetLevel(log.DebugLevel)
+	d := New(&Config{Logger: log.Log}, netxlite.DefaultResolver)
+	txp := &http.Transport{DialContext: d.DialContext}
+	client := &http.Client{Transport: txp}
+	resp, err := client.Get("http://www.google.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+}

internal/engine/netx/dialer/doc.go

@@ -1,4 +0,0 @@
-// Package dialer allows you to create a net.Dialer-compatible
-// DialContext-enabled dialer with error wrapping, optional logging,
-// optional network-events saving, and optional proxying.
-package dialer

internal/engine/netx/dialer/example_test.go

@@ -1,30 +0,0 @@
-package dialer_test
-
-import (
-	"context"
-
-	"github.com/apex/log"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/dialer"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-)
-
-func Example() {
-	saver := &trace.Saver{}
-
-	dlr := dialer.New(&dialer.Config{
-		DialSaver:      saver,
-		Logger:         log.Log,
-		ReadWriteSaver: saver,
-	}, netxlite.DefaultResolver)
-
-	ctx := context.Background()
-	conn, err := dlr.DialContext(ctx, "tcp", "8.8.8.8:53")
-	if err != nil {
-		log.WithError(err).Fatal("DialContext failed")
-	}
-
-	// ... use the connection ...
-
-	conn.Close()
-}

internal/engine/netx/dialer/integration_test.go

@@ -1,25 +0,0 @@
-package dialer_test
-
-import (
-	"net/http"
-	"testing"
-
-	"github.com/apex/log"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/dialer"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-)
-
-func TestDialerNewSuccess(t *testing.T) {
-	if testing.Short() {
-		t.Skip("skip test in short mode")
-	}
-	log.SetLevel(log.DebugLevel)
-	d := dialer.New(&dialer.Config{Logger: log.Log}, netxlite.DefaultResolver)
-	txp := &http.Transport{DialContext: d.DialContext}
-	client := &http.Client{Transport: txp}
-	resp, err := client.Get("http://www.google.com")
-	if err != nil {
-		t.Fatal(err)
-	}
-	resp.Body.Close()
-}

internal/engine/netx/dialer/proxy.go

@@ -1,5 +0,0 @@
-package dialer
-
-import "github.com/ooni/probe-cli/v3/internal/netxlite"
-
-type proxyDialer = netxlite.MaybeProxyDialer