cmd/go/internal/web: split interceptor into separate package

This moves the interception code ito package
cmd/go/internal/web/intercept so that it can also be used by
cmd/go/internal/auth.

For #26232

Change-Id: Id8148fca56f48adaf98ddd09a62657c08f890441
Reviewed-on: https://go-review.googlesource.com/c/go/+/625036
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/cmd/go/go_test.go

@@ -39,7 +39,7 @@ import (
 	"cmd/go/internal/toolchain"
 	"cmd/go/internal/vcs"
 	"cmd/go/internal/vcweb/vcstest"
-	"cmd/go/internal/web"
+	"cmd/go/internal/web/intercept"
 	"cmd/go/internal/work"
 	"cmd/internal/robustio"
 	"cmd/internal/sys"
@@ -145,13 +145,13 @@ func TestMain(m *testing.M) {
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "loading certificates from $TESTGO_VCSTEST_CERT: %v", err)
 			}
-			var interceptors []web.Interceptor
+			var interceptors []intercept.Interceptor
 			for _, host := range vcstest.Hosts {
 				interceptors = append(interceptors,
-					web.Interceptor{Scheme: "http", FromHost: host, ToHost: vcsTestHost},
-					web.Interceptor{Scheme: "https", FromHost: host, ToHost: vcsTestTLSHost, Client: vcsTestClient})
+					intercept.Interceptor{Scheme: "http", FromHost: host, ToHost: vcsTestHost},
+					intercept.Interceptor{Scheme: "https", FromHost: host, ToHost: vcsTestTLSHost, Client: vcsTestClient})
 			}
-			web.EnableTestHooks(interceptors)
+			intercept.EnableTestHooks(interceptors)
 		}
 
 		cmdgo.Main()

src/cmd/go/internal/vcweb/vcstest/vcstest.go

@@ -9,7 +9,7 @@ package vcstest
 import (
 	"cmd/go/internal/vcs"
 	"cmd/go/internal/vcweb"
-	"cmd/go/internal/web"
+	"cmd/go/internal/web/intercept"
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/pem"
@@ -101,13 +101,13 @@ func NewServer() (srv *Server, err error) {
 	vcs.VCSTestRepoURL = srv.HTTP.URL
 	vcs.VCSTestHosts = Hosts
 
-	interceptors := make([]web.Interceptor, 0, 2*len(Hosts))
+	interceptors := make([]intercept.Interceptor, 0, 2*len(Hosts))
 	for _, host := range Hosts {
 		interceptors = append(interceptors,
-			web.Interceptor{Scheme: "http", FromHost: host, ToHost: httpURL.Host, Client: srv.HTTP.Client()},
-			web.Interceptor{Scheme: "https", FromHost: host, ToHost: httpsURL.Host, Client: srv.HTTPS.Client()})
+			intercept.Interceptor{Scheme: "http", FromHost: host, ToHost: httpURL.Host, Client: srv.HTTP.Client()},
+			intercept.Interceptor{Scheme: "https", FromHost: host, ToHost: httpsURL.Host, Client: srv.HTTPS.Client()})
 	}
-	web.EnableTestHooks(interceptors)
+	intercept.EnableTestHooks(interceptors)
 
 	fmt.Fprintln(os.Stderr, "vcs-test.golang.org rerouted to "+srv.HTTP.URL)
 	fmt.Fprintln(os.Stderr, "https://vcs-test.golang.org rerouted to "+srv.HTTPS.URL)
@@ -121,7 +121,7 @@ func (srv *Server) Close() error {
 	}
 	vcs.VCSTestRepoURL = ""
 	vcs.VCSTestHosts = nil
-	web.DisableTestHooks()
+	intercept.DisableTestHooks()
 
 	srv.HTTP.Close()
 	srv.HTTPS.Close()

src/cmd/go/internal/web/http.go

@@ -27,6 +27,7 @@ import (
 	"cmd/go/internal/auth"
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
+	"cmd/go/internal/web/intercept"
 	"cmd/internal/browser"
 )
 
@@ -68,68 +69,10 @@ func checkRedirect(req *http.Request, via []*http.Request) error {
 		return errors.New("stopped after 10 redirects")
 	}
 
-	interceptRequest(req)
+	intercept.Request(req)
 	return nil
 }
 
-type Interceptor struct {
-	Scheme   string
-	FromHost string
-	ToHost   string
-	Client   *http.Client
-}
-
-func EnableTestHooks(interceptors []Interceptor) error {
-	if enableTestHooks {
-		return errors.New("web: test hooks already enabled")
-	}
-
-	for _, t := range interceptors {
-		if t.FromHost == "" {
-			panic("EnableTestHooks: missing FromHost")
-		}
-		if t.ToHost == "" {
-			panic("EnableTestHooks: missing ToHost")
-		}
-	}
-
-	testInterceptors = interceptors
-	enableTestHooks = true
-	return nil
-}
-
-func DisableTestHooks() {
-	if !enableTestHooks {
-		panic("web: test hooks not enabled")
-	}
-	enableTestHooks = false
-	testInterceptors = nil
-}
-
-var (
-	enableTestHooks  = false
-	testInterceptors []Interceptor
-)
-
-func interceptURL(u *urlpkg.URL) (*Interceptor, bool) {
-	if !enableTestHooks {
-		return nil, false
-	}
-	for i, t := range testInterceptors {
-		if u.Host == t.FromHost && (u.Scheme == "" || u.Scheme == t.Scheme) {
-			return &testInterceptors[i], true
-		}
-	}
-	return nil, false
-}
-
-func interceptRequest(req *http.Request) {
-	if t, ok := interceptURL(req.URL); ok {
-		req.Host = req.URL.Host
-		req.URL.Host = t.ToHost
-	}
-}
-
 func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 	start := time.Now()
 
@@ -137,7 +80,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 		return getFile(url)
 	}
 
-	if enableTestHooks {
+	if intercept.TestHooksEnabled {
 		switch url.Host {
 		case "proxy.golang.org":
 			if os.Getenv("TESTGOPROXY404") == "1" {
@@ -159,7 +102,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 
 		default:
 			if os.Getenv("TESTGONETWORK") == "panic" {
-				if _, ok := interceptURL(url); !ok {
+				if _, ok := intercept.URL(url); !ok {
 					host := url.Host
 					if h, _, err := net.SplitHostPort(url.Host); err == nil && h != "" {
 						host = h
@@ -189,7 +132,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
 		if url.Scheme == "https" {
 			auth.AddCredentials(req)
 		}
-		t, intercepted := interceptURL(req.URL)
+		t, intercepted := intercept.URL(req.URL)
 		if intercepted {
 			req.Host = req.URL.Host
 			req.URL.Host = t.ToHost

src/cmd/go/internal/web/intercept/intercept.go

@@ -0,0 +1,72 @@
+package intercept
+
+import (
+	"errors"
+	"net/http"
+	"net/url"
+)
+
+// Interceptor is used to change the host, and maybe the client,
+// for a request to point to a test host.
+type Interceptor struct {
+	Scheme   string
+	FromHost string
+	ToHost   string
+	Client   *http.Client
+}
+
+// EnableTestHooks installs the given interceptors to be used by URL and Request.
+func EnableTestHooks(interceptors []Interceptor) error {
+	if TestHooksEnabled {
+		return errors.New("web: test hooks already enabled")
+	}
+
+	for _, t := range interceptors {
+		if t.FromHost == "" {
+			panic("EnableTestHooks: missing FromHost")
+		}
+		if t.ToHost == "" {
+			panic("EnableTestHooks: missing ToHost")
+		}
+	}
+
+	testInterceptors = interceptors
+	TestHooksEnabled = true
+	return nil
+}
+
+// DisableTestHooks disables the installed interceptors.
+func DisableTestHooks() {
+	if !TestHooksEnabled {
+		panic("web: test hooks not enabled")
+	}
+	TestHooksEnabled = false
+	testInterceptors = nil
+}
+
+var (
+	// TestHooksEnabled is true if interceptors are installed
+	TestHooksEnabled = false
+	testInterceptors []Interceptor
+)
+
+// URL returns the Interceptor to be used for a given URL.
+func URL(u *url.URL) (*Interceptor, bool) {
+	if !TestHooksEnabled {
+		return nil, false
+	}
+	for i, t := range testInterceptors {
+		if u.Host == t.FromHost && (u.Scheme == "" || u.Scheme == t.Scheme) {
+			return &testInterceptors[i], true
+		}
+	}
+	return nil, false
+}
+
+// Request updates the host to actually use for the request, if it is to be intercepted.
+func Request(req *http.Request) {
+	if t, ok := URL(req.URL); ok {
+		req.Host = req.URL.Host
+		req.URL.Host = t.ToHost
+	}
+}