feat: experiments logging improvements (#2049)

* feat: warn when enabling inactive experiments

* feat: TASK_ environment prefix

* feat: calculate experiment enabled/active instead of storing

* refactor: rename GetTaskVar to GetTaskEnv

* feat: experiments tests

internal/experiments/errors.go

@@ -0,0 +1,32 @@
+package experiments
+
+import (
+	"fmt"
+	"strings"
+)
+
+type InvalidValueError struct {
+	Name          string
+	AllowedValues []string
+	Value         string
+}
+
+func (err InvalidValueError) Error() string {
+	return fmt.Sprintf(
+		"task: Experiment %q has an invalid value %q (allowed values: %s)",
+		err.Name,
+		err.Value,
+		strings.Join(err.AllowedValues, ", "),
+	)
+}
+
+type InactiveError struct {
+	Name string
+}
+
+func (err InactiveError) Error() string {
+	return fmt.Sprintf(
+		"task: Experiment %q is inactive and cannot be enabled",
+		err.Name,
+	)
+}

internal/experiments/experiment.go

@@ -0,0 +1,56 @@
+package experiments
+
+import (
+	"fmt"
+	"slices"
+)
+
+type Experiment struct {
+	Name          string   // The name of the experiment.
+	AllowedValues []string // The values that can enable this experiment.
+	Value         string   // The version of the experiment that is enabled.
+}
+
+// New creates a new experiment with the given name and sets the values that can
+// enable it.
+func New(xName string, allowedValues ...string) Experiment {
+	value := getEnv(xName)
+	x := Experiment{
+		Name:          xName,
+		AllowedValues: allowedValues,
+		Value:         value,
+	}
+	xList = append(xList, x)
+	return x
+}
+
+func (x *Experiment) Enabled() bool {
+	return slices.Contains(x.AllowedValues, x.Value)
+}
+
+func (x *Experiment) Active() bool {
+	return len(x.AllowedValues) > 0
+}
+
+func (x Experiment) Valid() error {
+	if !x.Active() && x.Value != "" {
+		return &InactiveError{
+			Name: x.Name,
+		}
+	}
+	if !x.Enabled() && x.Value != "" {
+		return &InvalidValueError{
+			Name:          x.Name,
+			AllowedValues: x.AllowedValues,
+			Value:         x.Value,
+		}
+	}
+	return nil
+}
+
+func (x Experiment) String() string {
+	if x.Enabled() {
+		return fmt.Sprintf("on (%s)", x.Value)
+	}
+	return "off"
+}

internal/experiments/experiment_test.go

@@ -0,0 +1,74 @@
+package experiments_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/go-task/task/v3/internal/experiments"
+)
+
+func TestNew(t *testing.T) {
+	const (
+		exampleExperiment    = "EXAMPLE"
+		exampleExperimentEnv = "TASK_X_EXAMPLE"
+	)
+	tests := []struct {
+		name          string
+		allowedValues []string
+		value         string
+		wantEnabled   bool
+		wantActive    bool
+		wantValid     error
+	}{
+		{
+			name:        `[] allowed, value=""`,
+			wantEnabled: false,
+			wantActive:  false,
+		},
+		{
+			name:        `[] allowed, value="1"`,
+			value:       "1",
+			wantEnabled: false,
+			wantActive:  false,
+			wantValid: &experiments.InactiveError{
+				Name: exampleExperiment,
+			},
+		},
+		{
+			name:          `[1] allowed, value=""`,
+			allowedValues: []string{"1"},
+			wantEnabled:   false,
+			wantActive:    true,
+		},
+		{
+			name:          `[1] allowed, value="1"`,
+			allowedValues: []string{"1"},
+			value:         "1",
+			wantEnabled:   true,
+			wantActive:    true,
+		},
+		{
+			name:          `[1] allowed, value="2"`,
+			allowedValues: []string{"1"},
+			value:         "2",
+			wantEnabled:   false,
+			wantActive:    true,
+			wantValid: &experiments.InvalidValueError{
+				Name:          exampleExperiment,
+				AllowedValues: []string{"1"},
+				Value:         "2",
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Setenv(exampleExperimentEnv, tt.value)
+			x := experiments.New(exampleExperiment, tt.allowedValues...)
+			assert.Equal(t, exampleExperiment, x.Name)
+			assert.Equal(t, tt.wantEnabled, x.Enabled())
+			assert.Equal(t, tt.wantActive, x.Active())
+			assert.Equal(t, tt.wantValid, x.Valid())
+		})
+	}
+}

internal/experiments/experiments.go

@@ -2,28 +2,17 @@ package experiments
 
 import (
 	"fmt"
-	"io"
 	"os"
 	"path/filepath"
-	"slices"
 	"strings"
 
-	"github.com/Ladicle/tabwriter"
 	"github.com/joho/godotenv"
 	"github.com/spf13/pflag"
-
-	"github.com/go-task/task/v3/internal/logger"
 )
 
 const envPrefix = "TASK_X_"
 
-type Experiment struct {
-	Name    string
-	Enabled bool
-	Value   string
-}
-
-// A list of experiments.
+// A set of experiments that can be enabled or disabled.
 var (
 	GentleForce     Experiment
 	RemoteTaskfiles Experiment
@@ -32,32 +21,31 @@ var (
 	EnvPrecedence   Experiment
 )
 
+// An internal list of all the initialized experiments used for iterating.
+var xList []Experiment
+
 func init() {
 	readDotEnv()
-	GentleForce = New("GENTLE_FORCE")
-	RemoteTaskfiles = New("REMOTE_TASKFILES")
-	AnyVariables = New("ANY_VARIABLES", "1", "2")
+	GentleForce = New("GENTLE_FORCE", "1")
+	RemoteTaskfiles = New("REMOTE_TASKFILES", "1")
+	AnyVariables = New("ANY_VARIABLES")
 	MapVariables = New("MAP_VARIABLES", "1", "2")
-	EnvPrecedence = New("ENV_PRECEDENCE")
+	EnvPrecedence = New("ENV_PRECEDENCE", "1")
 }
 
-func New(xName string, enabledValues ...string) Experiment {
-	if len(enabledValues) == 0 {
-		enabledValues = []string{"1"}
-	}
-	value := getEnv(xName)
-	return Experiment{
-		Name:    xName,
-		Enabled: slices.Contains(enabledValues, value),
-		Value:   value,
+// Validate checks if any experiments have been enabled while being inactive.
+// If one is found, the function returns an error.
+func Validate() error {
+	for _, x := range List() {
+		if err := x.Valid(); err != nil {
+			return err
+		}
 	}
+	return nil
 }
 
-func (x Experiment) String() string {
-	if x.Enabled {
-		return fmt.Sprintf("on (%s)", x.Value)
-	}
-	return "off"
+func List() []Experiment {
+	return xList
 }
 
 func getEnv(xName string) string {
@@ -95,18 +83,3 @@ func readDotEnv() {
 		}
 	}
 }
-
-func printExperiment(w io.Writer, l *logger.Logger, x Experiment) {
-	l.FOutf(w, logger.Yellow, "* ")
-	l.FOutf(w, logger.Green, x.Name)
-	l.FOutf(w, logger.Default, ": \t%s\n", x.String())
-}
-
-func List(l *logger.Logger) error {
-	w := tabwriter.NewWriter(os.Stdout, 0, 8, 0, ' ', 0)
-	printExperiment(w, l, GentleForce)
-	printExperiment(w, l, RemoteTaskfiles)
-	printExperiment(w, l, MapVariables)
-	printExperiment(w, l, EnvPrecedence)
-	return w.Flush()
-}