[#674] Add handling of variant parameter authorized values

- change param.variant type to string to be consistant with other params handling
- remove config/param_variant_test.go
- add variant.Select(string) to manage variant instance selection
- add UnsupportedVariantError (returned when variant name is not recognized)
- ensure TCR engine exits on error when variant is not recognized

src/config/tcr_config.go

@@ -28,7 +28,6 @@ import (
 	"github.com/murex/tcr/settings"
 	"github.com/murex/tcr/toolchain"
 	"github.com/murex/tcr/utils"
-	"github.com/murex/tcr/variant"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 	"io"
@@ -221,7 +220,7 @@ func UpdateEngineParams(p *params.Params) {
 	p.Toolchain = Config.Toolchain.GetValue()
 	p.PollingPeriod = Config.PollingPeriod.GetValue()
 	p.AutoPush = Config.AutoPush.GetValue()
-	p.Variant = variant.Variant(Config.Variant.GetValue())
+	p.Variant = Config.Variant.GetValue()
 	p.CommitFailures = Config.CommitFailures.GetValue()
 	p.VCS = Config.VCS.GetValue()
 	p.MessageSuffix = Config.MessageSuffix.GetValue()

src/engine/tcr.go

@@ -59,7 +59,7 @@ type (
 		ToggleAutoPush()
 		SetAutoPush(flag bool)
 		SetCommitOnFail(flag bool)
-		SetVariant(variant variant.Variant)
+		SetVariant(variant string)
 		GetCurrentRole() role.Role
 		RunAsDriver()
 		RunAsNavigator()
@@ -94,7 +94,7 @@ type (
 		// before starting a new one
 		roleMutex     sync.Mutex
 		commitOnFail  bool
-		variant       variant.Variant
+		variant       *variant.Variant
 		messageSuffix string
 		// shoot channel is used for handling interruptions coming from the UI
 		shoot chan bool
@@ -109,10 +109,6 @@ type (
 	}
 )
 
-func (tcr *TCREngine) SetVariant(variant variant.Variant) {
-	tcr.variant = variant
-}
-
 const traceReporterWaitingTime = 100 * time.Millisecond
 
 const fsWatchRearmDelay = 100 * time.Millisecond
@@ -200,6 +196,18 @@ func (tcr *TCREngine) SetCommitOnFail(flag bool) {
 	}
 }
 
+// SetVariant sets the TCR variant that will be used by TCR engine
+func (tcr *TCREngine) SetVariant(variantName string) {
+	var err error
+	tcr.variant, err = variant.Select(variantName)
+	if err != nil {
+		var unsupportedVariantError *variant.UnsupportedVariantError
+		if errors.As(err, &unsupportedVariantError) {
+			tcr.handleError(err, true, status.ConfigError)
+		}
+	}
+}
+
 func (tcr *TCREngine) setMobTimerDuration(duration time.Duration) {
 	if settings.EnableMobTimer {
 		if tcr.mode.IsMultiRole() {
@@ -633,14 +641,14 @@ func (tcr *TCREngine) revert(event events.TCREvent) {
 }
 
 func (tcr *TCREngine) noFilesRevertedMessage() string {
-	if tcr.variant == variant.Relaxed {
+	if *tcr.variant == variant.Relaxed {
 		return "No file reverted (only test files were updated since last commit)"
 	}
 	return "No file reverted"
 }
 
 func (tcr *TCREngine) shouldRevertFile(path string) bool {
-	return tcr.variant == variant.BTCR || tcr.language.IsSrcFile(path)
+	return *tcr.variant == variant.BTCR || tcr.language.IsSrcFile(path)
 }
 
 func (tcr *TCREngine) commitTestBreakingChanges(event events.TCREvent) (err error) {
@@ -694,7 +702,7 @@ func (tcr *TCREngine) GetSessionInfo() SessionInfo {
 		VCSSessionSummary: tcr.vcs.SessionSummary(),
 		GitAutoPush:       tcr.vcs.IsAutoPushEnabled(),
 		CommitOnFail:      tcr.commitOnFail,
-		Variant:           string(tcr.variant),
+		Variant:           tcr.variant.Name(),
 		MessageSuffix:     tcr.messageSuffix,
 	}
 }

src/engine/tcr_test.go

@@ -350,7 +350,7 @@ func Test_variant_specific_reverts(t *testing.T) {
 				},
 			)
 			tcr, vcsFake := initTCREngineWithFakesWithFileDiffs(
-				params.AParamSet(params.WithVariant(tt.variant)),
+				params.AParamSet(params.WithVariant(tt.variant.Name())),
 				nil, nil, nil, tt.fileDiffs)
 			tcr.revert(*events.ATcrEvent())
 			sniffer.Stop()
@@ -363,7 +363,7 @@ func Test_variant_specific_reverts(t *testing.T) {
 func Test_introspective_variant(t *testing.T) {
 	t.Skip("work in progress")
 	tcr, vcsFake := initTCREngineWithFakesWithFileDiffs(
-		params.AParamSet(params.WithVariant(variant.Introspective)),
+		params.AParamSet(params.WithVariant(variant.Introspective.Name())),
 		nil, nil, nil, vcs.FileDiffs{
 			vcs.NewFileDiff("fake-src", 1, 1),
 			vcs.NewFileDiff("fake-test", 1, 1),
@@ -589,7 +589,7 @@ func Test_set_variant(t *testing.T) {
 	for _, tt := range testFlags {
 		t.Run(fmt.Sprintf("Variant %v", tt.variant), func(t *testing.T) {
 			tcr, _ = initTCREngineWithFakes(nil, nil, nil, nil)
-			tcr.SetVariant(tt.variant)
+			tcr.SetVariant(tt.variant.Name())
 			assert.Equal(t, string(tt.variant), tcr.GetSessionInfo().Variant)
 		})
 	}

src/params/params.go

@@ -24,7 +24,6 @@ package params
 
 import (
 	"github.com/murex/tcr/runmode"
-	"github.com/murex/tcr/variant"
 	"time"
 )
 
@@ -37,7 +36,7 @@ type Params struct {
 	Toolchain       string
 	MobTurnDuration time.Duration
 	AutoPush        bool
-	Variant         variant.Variant
+	Variant         string
 	CommitFailures  bool
 	PollingPeriod   time.Duration
 	Mode            runmode.RunMode

src/params/params_test_data_builder.go

@@ -26,7 +26,6 @@ package params
 
 import (
 	"github.com/murex/tcr/runmode"
-	"github.com/murex/tcr/variant"
 	"time"
 )
 
@@ -40,7 +39,7 @@ func AParamSet(builders ...func(params *Params)) *Params {
 		Toolchain:       "",
 		MobTurnDuration: 0,
 		AutoPush:        false,
-		Variant:         variant.Relaxed,
+		Variant:         "relaxed",
 		PollingPeriod:   0,
 		Mode:            runmode.OneShot{},
 		VCS:             "git",
@@ -110,7 +109,7 @@ func WithAutoPush(value bool) func(params *Params) {
 }
 
 // WithVariant sets the provided value as the variant to be used
-func WithVariant(variant variant.Variant) func(params *Params) {
+func WithVariant(variant string) func(params *Params) {
 	return func(params *Params) {
 		params.Variant = variant
 	}

src/variant/variant.go

@@ -22,16 +22,45 @@ SOFTWARE.
 
 package variant
 
-// Variant represents the possible values for the TCR Variant
-// https://medium.com/@tdeniffel/tcr-variants-test-commit-revert-bf6bd84b17d3
-type Variant string
+import "fmt"
 
-func (v Variant) Name() string {
-	return string(v)
+// UnsupportedVariantError is returned when the provided Variant name is not supported.
+type UnsupportedVariantError struct {
+	variantName string
 }
 
+// Error returns the error description
+func (e *UnsupportedVariantError) Error() string {
+	return fmt.Sprintf("variant not supported: \"%s\"", e.variantName)
+}
+
+// Variant represents the possible values for the TCR Variant.
+// These values are inspired by the following blog-post:
+// https://medium.com/@tdeniffel/tcr-variants-test-commit-revert-bf6bd84b17d3
+type Variant string
+
+// Recognized variant values
 const (
 	Relaxed       Variant = "relaxed"
 	BTCR          Variant = "btcr"
 	Introspective Variant = "introspective"
 )
+
+var recognized = []Variant{Relaxed, BTCR, Introspective}
+
+// Select returns a variant instance for the provided name.
+// It returns an UnsupportedVariantError if the name is not recognized as a
+// valid variant name.
+func Select(name string) (*Variant, error) {
+	for _, variant := range recognized {
+		if name == variant.Name() {
+			return &variant, nil
+		}
+	}
+	return nil, &UnsupportedVariantError{name}
+}
+
+// Name returns the variant name
+func (v Variant) Name() string {
+	return string(v)
+}

src/variant/variant_test.go

@@ -44,3 +44,30 @@ func Test_get_variant_name(t *testing.T) {
 		})
 	}
 }
+
+func Test_select_variant(t *testing.T) {
+	relaxed, btcr, introspective := Relaxed, BTCR, Introspective
+	tests := []struct {
+		name            string
+		expectedVariant *Variant
+		expectedError   error
+	}{
+		{"relaxed", &relaxed, nil},
+		{"btcr", &btcr, nil},
+		{"introspective", &introspective, nil},
+		{"unknown", nil, &UnsupportedVariantError{"unknown"}},
+		{"", nil, &UnsupportedVariantError{""}},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			variant, err := Select(test.name)
+			assert.Equal(t, test.expectedVariant, variant)
+			assert.Equal(t, test.expectedError, err)
+		})
+	}
+}
+
+func Test_unsupported_variant_message_format(t *testing.T) {
+	err := UnsupportedVariantError{"some-variant"}
+	assert.Equal(t, "variant not supported: \"some-variant\"", err.Error())
+}