command: Add test for invalid selected workspace

If somehow an invalid workspace has been selected, the Meta.Workspace
method should not return an error, to ensure that we don't break any
existing workflows with invalid workspace names.

command/meta_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 
 	"github.com/hashicorp/terraform/backend"
+	"github.com/hashicorp/terraform/backend/local"
 	"github.com/hashicorp/terraform/terraform"
 )
 
@@ -238,6 +239,39 @@ func TestMeta_Workspace_override(t *testing.T) {
 	}
 }
 
+func TestMeta_Workspace_invalidSelected(t *testing.T) {
+	td := tempDir(t)
+	os.MkdirAll(td, 0755)
+	defer os.RemoveAll(td)
+	defer testChdir(t, td)()
+
+	// this is an invalid workspace name
+	workspace := "test workspace"
+
+	// create the workspace directories
+	if err := os.MkdirAll(filepath.Join(local.DefaultWorkspaceDir, workspace), 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	// create the workspace file to select it
+	if err := os.MkdirAll(DefaultDataDir, 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := ioutil.WriteFile(filepath.Join(DefaultDataDir, local.DefaultWorkspaceFile), []byte(workspace), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	m := new(Meta)
+
+	ws, err := m.Workspace()
+	if ws != workspace {
+		t.Errorf("Unexpected workspace\n got: %s\nwant: %s\n", ws, workspace)
+	}
+	if err != nil {
+		t.Errorf("Unexpected error: %s", err)
+	}
+}
+
 func TestMeta_process(t *testing.T) {
 	test = false
 	defer func() { test = true }()