internal/lsp: add regtest for golang/go#37984

This change also required the addition of a new run configuration -
WithEnv, which adds extra environment variables to the configuration.
Please let me know if this is the wrong approach.

Fixes golang/go#37984

Change-Id: Ied2a53a443dc74c7ed723b91765eeddc1a7c1c00
Reviewed-on: https://go-review.googlesource.com/c/tools/+/229128
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/lsp/cache/view.go

@@ -388,6 +388,9 @@ func (v *view) buildProcessEnv(ctx context.Context) (*imports.ProcessEnv, error)
 			processEnv.GOSUMDB = split[1]
 		}
 	}
+	if processEnv.GOPATH == "" {
+		return nil, fmt.Errorf("no GOPATH for view %s", v.folder)
+	}
 	return processEnv, nil
 }
 

internal/lsp/fake/workspace.go

@@ -34,6 +34,7 @@ type Workspace struct {
 	gopath   string
 	workdir  string
 	proxydir string
+	env      []string
 
 	watcherMu sync.Mutex
 	watchers  []func(context.Context, []FileEvent)
@@ -42,8 +43,11 @@ type Workspace struct {
 // NewWorkspace creates a named workspace populated by the txtar-encoded
 // content given by txt. It creates temporary directories for the workspace
 // content and for GOPATH.
-func NewWorkspace(name string, srctxt string, proxytxt string) (_ *Workspace, err error) {
-	w := &Workspace{name: name}
+func NewWorkspace(name, srctxt, proxytxt string, env ...string) (_ *Workspace, err error) {
+	w := &Workspace{
+		name: name,
+		env:  env,
+	}
 	defer func() {
 		// Clean up if we fail at any point in this constructor.
 		if err != nil {
@@ -219,12 +223,12 @@ func (w *Workspace) RemoveFile(ctx context.Context, path string) error {
 // GoEnv returns the environment variables that should be used for invoking Go
 // commands in the workspace.
 func (w *Workspace) GoEnv() []string {
-	return []string{
+	return append([]string{
 		"GOPATH=" + w.GOPATH(),
 		"GOPROXY=" + w.GOPROXY(),
 		"GO111MODULE=",
 		"GOSUMDB=off",
-	}
+	}, w.env...)
 }
 
 // RunGoCommand executes a go command in the workspace.

internal/lsp/regtest/diagnostics_test.go

@@ -344,3 +344,21 @@ func Hello() {
 		env.Await(env.DiagnosticAtRegexp("b/b.go", "x"))
 	})
 }
+
+func TestNoGOPATHIssue_37984(t *testing.T) {
+	const missingImport = `
+-- main.go --
+package main
+
+func _() {
+	fmt.Println("Hello World")
+}
+`
+	runner.Run(t, missingImport, func(t *testing.T, env *Env) {
+		env.OpenFile("main.go")
+		env.Await(env.DiagnosticAtRegexp("main.go", "fmt"))
+		if err := env.E.OrganizeImports(env.Ctx, "main.go"); err == nil {
+			t.Fatalf("organize imports should fail with an empty GOPATH")
+		}
+	}, WithEnv("GOPATH="))
+}

internal/lsp/regtest/env.go

@@ -161,6 +161,7 @@ type runConfig struct {
 	modes    EnvMode
 	proxyTxt string
 	timeout  time.Duration
+	env      []string
 }
 
 func (r *Runner) defaultConfig() *runConfig {
@@ -202,6 +203,12 @@ func WithModes(modes EnvMode) RunOption {
 	})
 }
 
+func WithEnv(env ...string) RunOption {
+	return optionSetter(func(opts *runConfig) {
+		opts.env = env
+	})
+}
+
 // Run executes the test function in the default configured gopls execution
 // modes. For each a test run, a new workspace is created containing the
 // un-txtared files specified by filedata.
@@ -233,7 +240,7 @@ func (r *Runner) Run(t *testing.T, filedata string, test func(t *testing.T, e *E
 			defer cancel()
 			ctx = debug.WithInstance(ctx, "", "")
 
-			ws, err := fake.NewWorkspace("regtest", filedata, config.proxyTxt)
+			ws, err := fake.NewWorkspace("regtest", filedata, config.proxyTxt, config.env...)
 			if err != nil {
 				t.Fatal(err)
 			}