internal/lsp: change -modfile flag to tempModfile

Remove double negative issues and rename the disableTempModfile flag
to be tempModfile.

Updates golang/go#31999

Change-Id: Id62aa3707fef6758a1026c864a962f0bed36bc2b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/212240
Run-TryBot: Rohan Challa <rohan@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cache/modfiles.go

@@ -37,7 +37,7 @@ func modfileFlagExists(ctx context.Context, folder string, env []string) (string
 
 // The function getModfiles will return the go.mod files associated with the directory that is passed in.
 func getModfiles(ctx context.Context, folder string, options source.Options) (*modfiles, error) {
-	if options.DisableTempModfile {
+	if !options.TempModfile {
 		log.Print(ctx, "using the -modfile flag is disabled", telemetry.Directory.Of(folder))
 		return nil, nil
 	}

internal/lsp/source/options.go

@@ -67,11 +67,11 @@ var (
 			Literal:       true,
 			Budget:        100 * time.Millisecond,
 		},
-		ComputeEdits:       myers.ComputeEdits,
-		Analyzers:          defaultAnalyzers,
-		GoDiff:             true,
-		LinkTarget:         "pkg.go.dev",
-		DisableTempModfile: true,
+		ComputeEdits: myers.ComputeEdits,
+		Analyzers:    defaultAnalyzers,
+		GoDiff:       true,
+		LinkTarget:   "pkg.go.dev",
+		TempModfile:  false,
 	}
 )
 
@@ -117,7 +117,7 @@ type Options struct {
 	// WARNING: This configuration will be changed in the future.
 	// It only exists while this feature is under development.
 	// Disable use of the -modfile flag in Go 1.14.
-	DisableTempModfile bool
+	TempModfile bool
 
 	LinkTarget string
 }
@@ -323,8 +323,8 @@ func (o *Options) set(name string, value interface{}) OptionResult {
 	case "verboseOutput":
 		result.setBool(&o.VerboseOutput)
 
-	case "disableTempModfile":
-		result.setBool(&o.DisableTempModfile)
+	case "tempModfile":
+		result.setBool(&o.TempModfile)
 
 	// Deprecated settings.
 	case "wantSuggestedFixes":