internal/lsp: add a configuration to limit workspace scope to root URI

Some users may intentionally be opening subdirectories to avoid having
gopls load the whole module. Allow this via a configuration.

Fixes golang/go#40567

Change-Id: I6167f62a74a1c0b7cf07c1cb247adda839ee41f2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/247617
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

gopls/doc/settings.md

@@ -50,19 +50,28 @@ Default: `false`.
 
 This controls where points documentation for given package in `textDocument/documentLink`.
 It might be one of:
+
 * `"godoc.org"`
 * `"pkg.go.dev"`
 If company chooses to use its own `godoc.org`, its address can be used as well.
 
 Default: `"pkg.go.dev"`.
 
-### **local** string
+### **local** *string*
 
 This is the equivalent of the `goimports -local` flag, which puts imports beginning with this string after 3rd-party packages.
 It should be the prefix of the import path whose imports should be grouped separately.
 
 Default: `""`.
 
+### **expandWorkspaceToModule** *boolean*
+
+This is true if `gopls` should expand the scope of the workspace to include the
+modules containing the workspace folders. Set this to false to avoid loading
+your entire module. This is particularly useful for those working in a monorepo.
+
+Default: `true`.
+
 ## Experimental
 
 The below settings are considered experimental. They may be deprecated or changed in the future. They are typically used to test experimental opt-in features or to disable features.

internal/lsp/cache/session.go

@@ -193,7 +193,7 @@ func (s *Session) createView(ctx context.Context, name string, folder span.URI,
 		v.session.cache.options(&v.options)
 	}
 	// Set the module-specific information.
-	if err := v.setBuildInformation(ctx, folder, options.Env, v.options.TempModfile); err != nil {
+	if err := v.setBuildInformation(ctx, folder, options); err != nil {
 		return nil, nil, func() {}, err
 	}
 

internal/lsp/cache/view.go

@@ -743,12 +743,12 @@ func (v *View) maybeReinitialize() {
 	v.initializeOnce = &once
 }
 
-func (v *View) setBuildInformation(ctx context.Context, folder span.URI, env []string, modfileFlagEnabled bool) error {
+func (v *View) setBuildInformation(ctx context.Context, folder span.URI, options source.Options) error {
 	if err := checkPathCase(folder.Filename()); err != nil {
 		return fmt.Errorf("invalid workspace configuration: %w", err)
 	}
 	// Make sure to get the `go env` before continuing with initialization.
-	modFile, err := v.setGoEnv(ctx, env)
+	modFile, err := v.setGoEnv(ctx, options.Env)
 	if err != nil {
 		return err
 	}
@@ -763,7 +763,7 @@ func (v *View) setBuildInformation(ctx context.Context, folder span.URI, env []s
 	}
 
 	v.root = v.folder
-	if v.modURI != "" {
+	if options.ExpandWorkspaceToModule && v.modURI != "" {
 		v.root = span.URIFromPath(filepath.Dir(v.modURI.Filename()))
 	}
 
@@ -772,7 +772,7 @@ func (v *View) setBuildInformation(ctx context.Context, folder span.URI, env []s
 	v.setBuildConfiguration()
 
 	// The user has disabled the use of the -modfile flag or has no go.mod file.
-	if !modfileFlagEnabled || v.modURI == "" {
+	if !options.TempModfile || v.modURI == "" {
 		return nil
 	}
 	if modfileFlag, err := v.modfileFlagExists(ctx, v.Options().Env); err != nil {

internal/lsp/fake/editor.go

@@ -69,6 +69,10 @@ type EditorConfig struct {
 	// config option.
 	SymbolMatcher *string
 
+	// LimitWorkspaceScope is true if the user does not want to expand their
+	// workspace scope to the entire module.
+	LimitWorkspaceScope bool
+
 	// WithoutWorkspaceFolders is used to simulate opening a single file in the
 	// editor, without a workspace root. In that case, the client sends neither
 	// workspace folders nor a root URI.
@@ -170,6 +174,7 @@ func (e *Editor) configuration() map[string]interface{} {
 	config := map[string]interface{}{
 		"verboseWorkDoneProgress": true,
 		"env":                     e.overlayEnv(),
+		"expandWorkspaceToModule": !e.Config.LimitWorkspaceScope,
 	}
 
 	if e.Config.CodeLens != nil {

internal/lsp/regtest/diagnostics_test.go

@@ -1118,3 +1118,33 @@ func main() {}
 		)
 	})
 }
+
+// This tests the functionality of the "limitWorkspaceScope"
+func TestLimitWorkspaceScope(t *testing.T) {
+	const mod = `
+-- go.mod --
+module mod.com
+-- a/main.go --
+package main
+
+func main() {}
+-- main.go --
+package main
+
+func main() {
+	var x int
+}
+`
+	withOptions(WithRootPath("a")).run(t, mod, func(t *testing.T, env *Env) {
+		env.OpenFile("a/main.go")
+		env.Await(
+			env.DiagnosticAtRegexp("main.go", "x"),
+		)
+	})
+	withOptions(WithRootPath("a"), WithLimitWorkspaceScope()).run(t, mod, func(t *testing.T, env *Env) {
+		env.OpenFile("a/main.go")
+		env.Await(
+			NoDiagnostics("main.go"),
+		)
+	})
+}

internal/lsp/regtest/runner.go

@@ -194,6 +194,13 @@ func WithGOPROXY(goproxy string) RunOption {
 	})
 }
 
+// WithLimitWorkspaceScope sets the LimitWorkspaceScope configuration.
+func WithLimitWorkspaceScope() RunOption {
+	return optionSetter(func(opts *runConfig) {
+		opts.editor.LimitWorkspaceScope = true
+	})
+}
+
 type TestFunc func(t *testing.T, env *Env)
 
 // Run executes the test function in the default configured gopls execution

internal/lsp/source/options.go

@@ -104,6 +104,7 @@ func DefaultOptions() Options {
 				CommandRegenerateCgo.Name:     true,
 				CommandToggleDetails.Name:     false,
 			},
+			ExpandWorkspaceToModule: true,
 		},
 		DebuggingOptions: DebuggingOptions{
 			CompletionBudget:   100 * time.Millisecond,
@@ -226,6 +227,10 @@ type UserOptions struct {
 
 	// Gofumpt indicates if we should run gofumpt formatting.
 	Gofumpt bool
+
+	// ExpandWorkspaceToModule is true if we should expand the scope of the
+	// workspace to include the modules containing the workspace folders.
+	ExpandWorkspaceToModule bool
 }
 
 type ImportShortcut int
@@ -576,6 +581,9 @@ func (o *Options) set(name string, value interface{}) OptionResult {
 	case "gofumpt":
 		result.setBool(&o.Gofumpt)
 
+	case "expandWorkspaceToModule":
+		result.setBool(&o.ExpandWorkspaceToModule)
+
 	// Replaced settings.
 	case "experimentalDisabledAnalyses":
 		result.State = OptionDeprecated