cleanup(netx): remove unused proxy-via-context codepath (#367)

We always set the proxy explicitly now. So, let us remove this
extra bit of code we're not using.

Part of https://github.com/ooni/probe/issues/1507.

internal/engine/httpx/jsonapi.go

@@ -10,8 +10,6 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/url"
-
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/dialer"
 )
 
 // Logger is the definition of Logger used by this package.
@@ -40,10 +38,6 @@ type Client struct {
 	// Logger is the logger to use.
 	Logger Logger
 
-	// ProxyURL allows to force a proxy URL to fallback to a
-	// tunnel, e.g., Psiphon.
-	ProxyURL *url.URL
-
 	// UserAgent is the user agent to use.
 	UserAgent string
 }
@@ -93,11 +87,6 @@ func (c Client) NewRequest(ctx context.Context, method, resourcePath string,
 		request.Header.Set("Accept", c.Accept)
 	}
 	request.Header.Set("User-Agent", c.UserAgent)
-	// Implementation note: the following allows tunneling if c.ProxyURL
-	// is not nil. Because the proxy URL is set as part of each request
-	// generated using this function, every request that eventually needs
-	// to reconnect will always do so using the proxy.
-	ctx = dialer.WithProxyURL(ctx, c.ProxyURL)
 	return request.WithContext(ctx), nil
 }
 

internal/engine/httpx/jsonapi_test.go

@@ -10,9 +10,7 @@ import (
 	"testing"
 
 	"github.com/apex/log"
-	"github.com/google/go-cmp/cmp"
 	"github.com/ooni/probe-cli/v3/internal/engine/httpx"
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/dialer"
 )
 
 const userAgent = "miniooni/0.1.0-dev"
@@ -153,21 +151,6 @@ func TestNewRequestUserAgentIsSet(t *testing.T) {
 	}
 }
 
-func TestNewRequestTunnelingIsPossible(t *testing.T) {
-	client := newClient()
-	client.ProxyURL = &url.URL{Scheme: "socks5", Host: "[::1]:54321"}
-	req, err := client.NewRequest(
-		context.Background(), "GET", "/", nil, nil,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-	cmp := cmp.Diff(dialer.ContextProxyURL(req.Context()), client.ProxyURL)
-	if cmp != "" {
-		t.Fatal(cmp)
-	}
-}
-
 func TestClientDoJSONClientDoFailure(t *testing.T) {
 	expected := errors.New("mocked error")
 	client := newClient()
@@ -265,10 +248,6 @@ func TestCreateJSONSuccess(t *testing.T) {
 	}
 }
 
-type httpbinput struct {
-	Data string `json:"data"`
-}
-
 func TestUpdateJSONSuccess(t *testing.T) {
 	headers := httpbinheaders{
 		Headers: map[string]string{