userpreferences parsing/ls config handing

internal/fourslash/fourslash.go

@@ -42,6 +42,7 @@ type FourslashTest struct {
 	scriptInfos map[string]*scriptInfo
 	converters  *ls.Converters
 
+	userPreferences      *ls.UserPreferences
 	currentCaretPosition lsproto.Position
 	lastKnownMarkerName  *string
 	activeFilename       string
@@ -268,6 +269,29 @@ func sendRequest[Params, Resp any](t *testing.T, f *FourslashTest, info lsproto.
 	)
 	f.writeMsg(t, req.Message())
 	resp := f.readMsg(t)
+	if resp == nil {
+		return nil, *new(Resp), false
+	}
+
+	// currently, the only request that may be sent by the server during a client request is one `config` request
+	// !!! remove if `config` is handled in initialization and there are no other server-initiated requests
+	if resp.Kind == lsproto.MessageKindRequest {
+		req := resp.AsRequest()
+		switch req.Method {
+		case lsproto.MethodWorkspaceConfiguration:
+			req := lsproto.ResponseMessage{
+				ID:      req.ID,
+				JSONRPC: req.JSONRPC,
+				Result:  []any{f.userPreferences},
+			}
+			f.writeMsg(t, req.Message())
+			resp = f.readMsg(t)
+		default:
+			// other types of responses not yet used in fourslash; implement them if needed
+			t.Fatalf("Unexpected request received: %s", req)
+		}
+	}
+
 	if resp == nil {
 		return nil, *new(Resp), false
 	}
@@ -300,6 +324,21 @@ func (f *FourslashTest) readMsg(t *testing.T) *lsproto.Message {
 	return msg
 }
 
+func (f *FourslashTest) Configure(t *testing.T, config *ls.UserPreferences) {
+	f.userPreferences = config
+	sendNotification(t, f, lsproto.WorkspaceDidChangeConfigurationInfo, &lsproto.DidChangeConfigurationParams{
+		Settings: config,
+	})
+}
+
+func (f *FourslashTest) ConfigureWithReset(t *testing.T, config *ls.UserPreferences) (reset func()) {
+	originalConfig := f.userPreferences.Copy()
+	f.Configure(t, config)
+	return func() {
+		f.Configure(t, originalConfig)
+	}
+}
+
 func (f *FourslashTest) GoToMarkerOrRange(t *testing.T, markerOrRange MarkerOrRange) {
 	f.goToMarker(t, markerOrRange)
 }
@@ -541,6 +580,10 @@ func (f *FourslashTest) verifyCompletionsWorker(t *testing.T, expected *Completi
 		Position: f.currentCaretPosition,
 		Context:  &lsproto.CompletionContext{},
 	}
+	if expected != nil && expected.UserPreferences != nil {
+		reset := f.ConfigureWithReset(t, expected.UserPreferences)
+		defer reset()
+	}
 	resMsg, result, resultOk := sendRequest(t, f, lsproto.TextDocumentCompletionInfo, params)
 	if resMsg == nil {
 		t.Fatalf(prefix+"Nil response received for completion request", f.lastKnownMarkerName)
@@ -1449,6 +1492,12 @@ func (f *FourslashTest) getCurrentPositionPrefix() string {
 }
 
 func (f *FourslashTest) BaselineAutoImportsCompletions(t *testing.T, markerNames []string) {
+	reset := f.ConfigureWithReset(t, &ls.UserPreferences{
+		IncludeCompletionsForModuleExports:    core.TSTrue,
+		IncludeCompletionsForImportStatements: core.TSTrue,
+	})
+	defer reset()
+
 	for _, markerName := range markerNames {
 		f.GoToMarker(t, markerName)
 		params := &lsproto.CompletionParams{

internal/fourslash/tests/autoImportCompletion_test.go

@@ -40,6 +40,21 @@ a/**/
 		},
 	})
 	f.BaselineAutoImportsCompletions(t, []string{""})
+	f.VerifyCompletions(t, "", &fourslash.CompletionsExpectedList{
+		UserPreferences: &ls.UserPreferences{
+			// completion autoimport preferences off; this tests if fourslash server communication correctly registers changes in user preferences
+			IncludeCompletionsForModuleExports:    core.TSUnknown,
+			IncludeCompletionsForImportStatements: core.TSUnknown,
+		},
+		IsIncomplete: false,
+		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
+			CommitCharacters: &DefaultCommitCharacters,
+			EditRange:        Ignored,
+		},
+		Items: &fourslash.CompletionsExpectedItems{
+			Excludes: []string{"anotherVar"},
+		},
+	})
 }
 
 func TestAutoImportCompletion2(t *testing.T) {

internal/ls/host.go

@@ -1,10 +1,13 @@
 package ls
 
-import "github.com/microsoft/typescript-go/internal/sourcemap"
+import (
+	"github.com/microsoft/typescript-go/internal/sourcemap"
+)
 
 type Host interface {
 	UseCaseSensitiveFileNames() bool
 	ReadFile(path string) (contents string, ok bool)
 	Converters() *Converters
+	UserPreferences() *UserPreferences
 	GetECMALineInfo(fileName string) *sourcemap.ECMALineInfo
 }

internal/ls/languageservice.go

@@ -30,6 +30,10 @@ func (l *LanguageService) GetProgram() *compiler.Program {
 	return l.program
 }
 
+func (l *LanguageService) UserPreferences() *UserPreferences {
+	return l.host.UserPreferences()
+}
+
 func (l *LanguageService) tryGetProgramAndFile(fileName string) (*compiler.Program, *ast.SourceFile) {
 	program := l.GetProgram()
 	file := program.GetSourceFile(fileName)