Refactor.

Change `redirect-console-to-file` to  `console-output`

Console/Env variables override `.js` config variables.
Add a method to initialise a file-based config
if  `console-output` is provided.

Update breaking test.

cmd/options.go

@@ -67,7 +67,7 @@ func optionFlagSet() *pflag.FlagSet {
 	flags.String("summary-time-unit", "", "define the time unit used to display the trend stats. Possible units are: 's', 'ms' and 'us'")
 	flags.StringSlice("system-tags", lib.DefaultSystemTagList, "only include these system tags in metrics")
 	flags.StringSlice("tag", nil, "add a `tag` to be applied to all samples, as `[name]=[value]`")
-	flags.String("redirect-console-to-file", "", "redirects the console logging to the provided file")
+	flags.String("console-output", "", "redirects the console logging to the provided output file")
 	flags.Bool("discard-response-bodies", false, "Read but don't process or save HTTP response bodies")
 	return flags
 }
@@ -175,13 +175,13 @@ func getOptions(flags *pflag.FlagSet) (lib.Options, error) {
 		opts.RunTags = stats.IntoSampleTags(&parsedRunTags)
 	}
 
-	redirectConFile, err := flags.GetString("redirect-console-to-file")
+	redirectConFile, err := flags.GetString("console-output")
 	if err != nil {
 		return opts, err
 	}
 
 	if redirectConFile != "" {
-		opts.RedirectConsoleToFile = null.StringFrom(redirectConFile)
+		opts.ConsoleOutput = null.StringFrom(redirectConFile)
 	}
 
 	return opts, nil

cmd/run.go

@@ -173,6 +173,14 @@ a commandline interface for interacting with it.`,
 		// Write options back to the runner too.
 		r.SetOptions(conf.Options)
 
+		// If we have a file-based console, we need to override the
+		// default console.
+		if conf.ConsoleOutput.Valid {
+			if err := r.InitConsole(); err != nil {
+				return err
+			}
+		}
+
 		// Create a local executor wrapping the runner.
 		fprintf(stdout, "%s executor\r", initBar.String())
 		ex := local.New(r)

js/console.go

@@ -27,7 +27,6 @@ import (
 
 	"github.com/dop251/goja"
 	log "github.com/sirupsen/logrus"
-	"github.com/spf13/afero"
 )
 
 type Console struct {
@@ -40,16 +39,10 @@ func NewConsole() *Console {
 }
 
 // NewFileConsole creates a console logger with its output set to the file at the provided `filepath`.
-func NewFileConsole(fs afero.Fs, filepath string) (*Console, error) {
-	f, err := fs.OpenFile(filepath, os.O_APPEND|os.O_WRONLY, os.ModeAppend)
+func NewFileConsole(filepath string) (*Console, error) {
+	f, err := os.OpenFile(filepath, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644)
 	if err != nil {
-		if os.IsNotExist(err) {
-			if f, err = fs.Create(filepath); err != nil {
-				return nil, err
-			}
-		} else {
-			return nil, err
-		}
+		return nil, err
 	}
 
 	l := log.New()

js/console_test.go

@@ -24,8 +24,11 @@ import (
 	"context"
 	"fmt"
 	"io/ioutil"
+	"os"
 	"testing"
 
+	"gopkg.in/guregu/null.v3"
+
 	"github.com/dop251/goja"
 	"github.com/loadimpact/k6/js/common"
 	"github.com/loadimpact/k6/lib"
@@ -146,17 +149,19 @@ func TestFileConsole(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			for args, result := range argsets {
 				t.Run(args, func(t *testing.T) {
-					mockFs := afero.NewMemMapFs()
 					r, err := New(&lib.SourceData{
 						Filename: "/script",
 						Data: []byte(fmt.Sprintf(
-							`export let options = {
-								redirectConsoleToFile: "%s",
-							};
-							export default function() { console.%s(%s); }`,
-							logFile, name, args,
+							`export default function() { console.%s(%s); }`,
+							name, args,
 						)),
-					}, mockFs, lib.RuntimeOptions{})
+					}, afero.NewMemMapFs(), lib.RuntimeOptions{})
+					assert.NoError(t, err)
+
+					r.SetOptions(lib.Options{
+						ConsoleOutput: null.StringFrom(logFile),
+					})
+					err = r.InitConsole()
 					assert.NoError(t, err)
 
 					samples := make(chan stats.SampleContainer, 100)
@@ -170,7 +175,7 @@ func TestFileConsole(t *testing.T) {
 					assert.NoError(t, err)
 
 					// Test if the file was created.
-					_, err = mockFs.Stat(logFile)
+					_, err = os.Stat(logFile)
 					assert.NoError(t, err)
 
 					entry := hook.LastEntry()
@@ -189,14 +194,16 @@ func TestFileConsole(t *testing.T) {
 						entryStr, err := entry.String()
 						assert.NoError(t, err)
 
-						f, err := mockFs.Open(logFile)
+						f, err := os.Open(logFile)
 						assert.NoError(t, err)
 
 						fileContent, err := ioutil.ReadAll(f)
 						assert.NoError(t, err)
 
 						assert.Equal(t, entryStr, string(fileContent))
 					}
+
+					os.Remove(logFile)
 				})
 			}
 		})

js/runner.go

@@ -84,16 +84,6 @@ func NewFromBundle(b *Bundle) (*Runner, error) {
 		return nil, err
 	}
 
-	// Initialise a console for the Runner.
-	var c *Console
-	if b.Options.RedirectConsoleToFile.Valid {
-		if c, err = NewFileConsole(b.BaseInitContext.fs, b.Options.RedirectConsoleToFile.String); err != nil {
-			return nil, err
-		}
-	} else {
-		c = NewConsole()
-	}
-
 	r := &Runner{
 		Bundle:       b,
 		Logger:       log.StandardLogger(),
@@ -104,10 +94,11 @@ func NewFromBundle(b *Bundle) (*Runner, error) {
 			DualStack: true,
 		},
 		Resolver: dnscache.New(0),
-		console:  c,
 	}
+
 	r.SetOptions(r.Bundle.Options)
-	return r, nil
+	err = r.InitConsole()
+	return r, err
 }
 
 func (r *Runner) MakeArchive() *lib.Archive {
@@ -281,6 +272,25 @@ func (r *Runner) SetOptions(opts lib.Options) {
 	}
 }
 
+// InitConsole initialises a console based on the runner config.
+func (r *Runner) InitConsole() error {
+	var (
+		c   *Console
+		err error
+	)
+
+	if r.Bundle.Options.ConsoleOutput.Valid {
+		if c, err = NewFileConsole(r.Bundle.Options.ConsoleOutput.String); err != nil {
+			return err
+		}
+	} else {
+		c = NewConsole()
+	}
+
+	r.console = c
+	return nil
+}
+
 // Runs an exported function in its own temporary VU, optionally with an argument. Execution is
 // interrupted if the context expires. No error is returned if the part does not exist.
 func (r *Runner) runPart(ctx context.Context, out chan<- stats.SampleContainer, name string, arg interface{}) (goja.Value, error) {

lib/options.go

@@ -274,7 +274,7 @@ type Options struct {
 	DiscardResponseBodies null.Bool `json:"discardResponseBodies" envconfig:"discard_response_bodies"`
 
 	// Redirect console logging to a file
-	RedirectConsoleToFile null.String `json:"redirectConsoleToFile" envconfig:"redirect_console_to_file"`
+	ConsoleOutput null.String `json:"-" envconfig:"console_output"`
 }
 
 // Returns the result of overwriting any fields with any that are set on the argument.
@@ -388,8 +388,8 @@ func (o Options) Apply(opts Options) Options {
 	if opts.DiscardResponseBodies.Valid {
 		o.DiscardResponseBodies = opts.DiscardResponseBodies
 	}
-	if opts.RedirectConsoleToFile.Valid {
-		o.RedirectConsoleToFile = opts.RedirectConsoleToFile
+	if opts.ConsoleOutput.Valid {
+		o.ConsoleOutput = opts.ConsoleOutput
 	}
 
 	return o

lib/runner.go

@@ -66,6 +66,9 @@ type Runner interface {
 	// values and write it back to the runner.
 	GetOptions() Options
 	SetOptions(opts Options)
+
+	//  Initialise a new console for the runner (stdout/file) based on the config.
+	InitConsole() error
 }
 
 // A VU is a Virtual User, that can be scheduled by an Executor.
@@ -142,6 +145,10 @@ func (r *MiniRunner) SetOptions(opts Options) {
 	r.Options = opts
 }
 
+func (r *MiniRunner) InitConsole() error {
+	return nil
+}
+
 // A VU spawned by a MiniRunner.
 type MiniRunnerVU struct {
 	R   MiniRunner