[elastic] Move the deps download into 'intialize' request handle

The original implementation relies on 'go list' to download the deps.
And 'go list' will be called by the request handler indirectly.
This approach is unpredictable and 'go list' is black box to us. So it's
better download the deps manually in 'ManageDeps', i.e. inside
'initialize' request handler.

If the client sends the initialize option `installGoDependency: true`,
download the deps in `initialize` handler.

If the client doesn't send the initialize option `installGoDependency: true`,
disable the network access by `GOPROXY=off` and find the deps from vendor
folder.

Author: Henry Wong

go/internal/packagesdriver/sizes.go

@@ -11,6 +11,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"go/types"
+	"golang.org/x/tools/internal/lsp/protocol"
 	"log"
 	"os"
 	"os/exec"
@@ -125,6 +126,7 @@ func InvokeGo(ctx context.Context, env []string, dir string, usesExportData bool
 	cmd.Dir = dir
 	cmd.Stdout = stdout
 	cmd.Stderr = stderr
+	protocol.AdjustGoListForVendorMode(&(cmd.Env), &(cmd.Args))
 	if err := cmd.Run(); err != nil {
 		exitErr, ok := err.(*exec.ExitError)
 		if !ok {

go/packages/golist.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"go/types"
+	"golang.org/x/tools/internal/lsp/protocol"
 	"hash/fnv"
 	"io/ioutil"
 	"log"
@@ -860,7 +861,7 @@ func invokeGo(cfg *Config, args ...string) (*bytes.Buffer, error) {
 	defer func(start time.Time) {
 		cfg.Logf("%s for %v, stderr: <<%s>>\n", time.Since(start), cmdDebugStr(cmd, args...), stderr)
 	}(time.Now())
-
+	protocol.AdjustGoListForVendorMode(&(cmd.Env), &(cmd.Args))
 	if err := cmd.Run(); err != nil {
 		// Check for 'go' executable not being found.
 		if ee, ok := err.(*exec.Error); ok && ee.Err == exec.ErrNotFound {

internal/lsp/cache/session.go

@@ -93,6 +93,11 @@ func (s *session) NewView(ctx context.Context, name string, folder span.URI) sou
 		},
 		ignoredURIs: make(map[span.URI]struct{}),
 	}
+	if enableVendor, ok := ctx.Value("ENABLEVENDOR").(bool); ok && enableVendor {
+		// Set 'GOPROXY=off' to disable the network access
+		v.env = append(v.env, "GOPROXY=off")
+		v.env = append(v.env, "ENABLEVENDOR=on")
+	}
 	// Preemptively build the builtin package,
 	// so we immediately add builtin.go to the list of ignored files.
 	v.buildBuiltinPkg(ctx)

internal/lsp/elasticserver.go

@@ -189,10 +189,8 @@ type WorkspaceFolderMeta struct {
 // manageDeps will try its best to convert the folders to modules. The core functions, like deps downloading and deps
 // management, will be implemented in the package 'cache'.
 func (s ElasticServer) ManageDeps(folders *[]protocol.WorkspaceFolder) error {
-	// Note: For the upstream go langserver, granularity of the workspace folders is repository. But for the elastic go
-	// language server, there are repositories contain multiple modules. In order to handle the modules separately, we
-	// consider different modules as different workspace folders, so we can manage the dependency of different modules
-	// separately.
+	// In order to handle the modules separately, we consider different modules as different workspace folders, so we
+	// can manage the dependency of different modules separately.
 	for _, folder := range *folders {
 		metadata := &WorkspaceFolderMeta{}
 		if folder.URI != "" {

internal/lsp/general.go

@@ -38,6 +38,9 @@ func (s *Server) initialize(ctx context.Context, params *protocol.InitializePara
 		if opt, ok := opts["noIncrementalSync"].(bool); ok && opt {
 			s.textDocumentSyncKind = protocol.Full
 		}
+		if opt, ok := opts["installGoDependency"].(bool); ok && opt {
+			s.installGoDependency = true
+		}
 	}
 
 	// Default to using synopsis as a default for hover information.

internal/lsp/protocol/elasticserver.go

@@ -14,6 +14,22 @@ type ElasticServer interface {
 	ManageDeps(folders *[]WorkspaceFolder) error
 }
 
+func AdjustGoListForVendorMode(env *[]string, args *[]string) {
+	l := len(*env)
+	for i := range *env {
+		if (*env)[l-i-1] == "ENABLEVENDOR=on" {
+			// If 'ENABLEVENDOR' is on, append '-mod=vendor' to go list command
+			for j := range *args {
+				if (j+2 < len(*args)) && (*args)[j] == "go" && (*args)[j+1] == "list" {
+					*args = append((*args)[:j+2], append([]string{"-mod=vendor"}, (*args)[j+2:]...)...)
+					break
+				}
+			}
+			return
+		}
+	}
+}
+
 type elasticServerHandler struct {
 	canceller
 	server ElasticServer

internal/lsp/server.go

@@ -88,6 +88,7 @@ type Server struct {
 	preferredContentFormat        protocol.MarkupKind
 	disabledAnalyses              map[string]struct{}
 	wantSuggestedFixes            bool
+	installGoDependency           bool
 
 	supportedCodeActions map[source.FileKind]map[protocol.CodeActionKind]bool
 

internal/lsp/workspace.go

@@ -8,8 +8,10 @@ import (
 	"context"
 
 	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/lsp/telemetry/log"
 	"golang.org/x/tools/internal/span"
 	errors "golang.org/x/xerrors"
+	"os/exec"
 )
 
 func (s *Server) changeFolders(ctx context.Context, event protocol.WorkspaceFoldersChangeEvent) error {
@@ -31,6 +33,16 @@ func (s *Server) changeFolders(ctx context.Context, event protocol.WorkspaceFold
 }
 
 func (s *Server) addView(ctx context.Context, name string, uri span.URI) error {
+	if s.installGoDependency {
+		cmd := exec.Command("go", "mod", "download")
+		cmd.Dir = uri.Filename()
+		if err := cmd.Run(); err != nil {
+			log.Error(ctx, "failed to download the dependencies", err)
+		}
+	} else {
+		// If we disable the go dependency download, trying to find the deps from the vendor folder.
+		ctx = context.WithValue(ctx, "ENABLEVENDOR", true)
+	}
 	view := s.session.NewView(ctx, name, uri)
 	s.stateMu.Lock()
 	state := s.state