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

The original implementation relies on 'go list' to download the deps.
'go list' is called by other 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.

For security, set 'GO111MODULE=off' by default, 'GO111MODULE=off' will
disable the deps download by inconsistencies.

NOTE:'GO111MODULE=off' break the go langserver ability in some extent.
The official option for disable the network access is setting
'GOPROXY=off' under mod mode, however this option will break the go
langserver totally. Related issue: golang/go#32337

internal/lsp/cache/session.go

@@ -65,7 +65,7 @@ func (s *session) Cache() source.Cache {
 	return s.cache
 }
 
-func (s *session) NewView(ctx context.Context, name string, folder span.URI) source.View {
+func (s *session) NewView(ctx context.Context, name string, folder span.URI, installGoDeps bool) source.View {
 	index := atomic.AddInt64(&viewIndex, 1)
 	s.viewMu.Lock()
 	defer s.viewMu.Unlock()
@@ -93,6 +93,16 @@ func (s *session) NewView(ctx context.Context, name string, folder span.URI) sou
 		},
 		ignoredURIs: make(map[span.URI]struct{}),
 	}
+
+	if installGoDeps {
+		v.env = append(v.env, "GO111MODULE=on")
+	} else {
+		// Setting 'GO111MODULE=off' by default. 'GO111MODULE=off' is inconsistent with module mode, this will disable
+		// the deps download.
+		// TODO(henrywong) Use 'GOPROXY=off' to disable the network access
+		v.env = append(v.env, "GO111MODULE=off")
+	}
+
 	// Preemptively build the builtin package,
 	// so we immediately add builtin.go to the list of ignored files.
 	v.buildBuiltinPkg(ctx)

internal/lsp/elasticext_test.go

@@ -60,7 +60,7 @@ func testLSPExt(t *testing.T, exporter packagestest.Exporter) {
 
 	cache := cache.New()
 	session := cache.NewSession(ctx)
-	view := session.NewView(cfg.Context, extViewName, span.FileURI(cfg.Dir))
+	view := session.NewView(cfg.Context, extViewName, span.FileURI(cfg.Dir), false)
 	view.SetEnv(cfg.Env)
 	s := &Server{
 		session:     session,

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/lsp_test.go

@@ -43,7 +43,7 @@ func testLSP(t *testing.T, exporter packagestest.Exporter) {
 
 	cache := cache.New()
 	session := cache.NewSession(ctx)
-	view := session.NewView(ctx, viewName, span.FileURI(data.Config.Dir))
+	view := session.NewView(ctx, viewName, span.FileURI(data.Config.Dir), false)
 	view.SetEnv(data.Config.Env)
 	for filename, content := range data.Config.Overlay {
 		session.SetOverlay(span.FileURI(filename), content)

internal/lsp/protocol/elasticserver.go

@@ -11,7 +11,7 @@ type ElasticServer interface {
 	Server
 	EDefinition(context.Context, *TextDocumentPositionParams) ([]SymbolLocator, error)
 	Full(context.Context, *FullParams) (FullResponse, error)
-	ManageDeps(folders *[]WorkspaceFolder) error
+	ManageDeps(*[]WorkspaceFolder) error
 }
 
 type elasticServerHandler struct {

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/source/view.go

@@ -130,7 +130,7 @@ type Cache interface {
 // A session may have many active views at any given time.
 type Session interface {
 	// NewView creates a new View and returns it.
-	NewView(ctx context.Context, name string, folder span.URI) View
+	NewView(ctx context.Context, name string, folder span.URI, installGoDeps bool) View
 
 	// Cache returns the cache that created this session.
 	Cache() Cache

internal/lsp/workspace.go

@@ -6,10 +6,11 @@ package lsp
 
 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 {
@@ -31,7 +32,14 @@ func (s *Server) changeFolders(ctx context.Context, event protocol.WorkspaceFold
 }
 
 func (s *Server) addView(ctx context.Context, name string, uri span.URI) error {
-	view := s.session.NewView(ctx, name, uri)
+	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)
+		}
+	}
+	view := s.session.NewView(ctx, name, uri, s.installGoDependency)
 	s.stateMu.Lock()
 	state := s.state
 	s.stateMu.Unlock()