internal/lsp: turn tempModfile flag on by default

This change turns the tempModfile flag on by default in the master branch.

Change-Id: If96369aee4e970421a80d5ff89385a38c7ccf0b2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/219225
Run-TryBot: Rohan Challa <rohan@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cache/view.go

@@ -591,8 +591,8 @@ func (v *view) setBuildInformation(ctx context.Context, folder span.URI, env []s
 	// check if the view has a valid build configuration.
 	v.hasValidBuildConfiguration = checkBuildConfiguration(v.goCommand, v.realMod, v.folder, v.gopath)
 
-	// The user has disabled the use of the -modfile flag.
-	if !modfileFlagEnabled {
+	// The user has disabled the use of the -modfile flag or has no go.mod file.
+	if !modfileFlagEnabled || v.realMod == "" {
 		return nil
 	}
 	if modfileFlag, err := v.modfileFlagExists(ctx, v.Options().Env); err != nil {

internal/lsp/lsp_test.go

@@ -51,7 +51,6 @@ func testLSP(t *testing.T, exporter packagestest.Exporter) {
 		cache := cache.New(nil)
 		session := cache.NewSession()
 		options := tests.DefaultOptions()
-		options.TempModfile = exporter == packagestest.Modules
 		session.SetOptions(options)
 		options.Env = datum.Config.Env
 		v, _, err := session.NewView(ctx, datum.Config.Dir, span.FileURI(datum.Config.Dir), options)

internal/lsp/source/options.go

@@ -82,7 +82,7 @@ func DefaultOptions() Options {
 			CompletionBudget: 100 * time.Millisecond,
 		},
 		ExperimentalOptions: ExperimentalOptions{
-			TempModfile: false,
+			TempModfile: true,
 		},
 		Hooks: Hooks{
 			ComputeEdits: myers.ComputeEdits,