make testcase.Var#ID a dedicated type

Many code editors’ intellisense often prioritised suggesting Var[string]#ID for string values instead of Var[string]#Get,
which can easily lead to headaches when auto-completion accidentally selects the wrong option.

Spec_test.go

@@ -127,7 +127,7 @@ func TestSpec_Context(t *testing.T) {
 	var allSideEffect [][]string
 	var sideEffect []string
 
-	v := testcase.Var[int]{ID: strconv.Itoa(rand.Int())}
+	v := testcase.Var[int]{ID: testcase.VarID(strconv.Itoa(rand.Int()))}
 	nest1Value := rand.Int()
 	nest2Value := rand.Int()
 	nest3Value := rand.Int()
@@ -226,7 +226,7 @@ func TestSpec_ParallelSafeVariableSupport(t *testing.T) {
 	s := testcase.NewSpec(t)
 	s.Parallel()
 
-	v := testcase.Var[int]{ID: strconv.Itoa(rand.Int())}
+	v := testcase.Var[int]{ID: testcase.VarID(strconv.Itoa(rand.Int()))}
 	nest1Value := rand.Int()
 	nest2Value := rand.Int()
 	nest3Value := rand.Int()

T.go

@@ -159,7 +159,7 @@ func (t *T) contexts() []*Spec {
 	return t.cache.contexts
 }
 
-func (t *T) hasOnLetHookApplied(name string) bool {
+func (t *T) hasOnLetHookApplied(name VarID) bool {
 	for _, c := range t.contexts() {
 		if ok := c.vars.hasOnLetHookApplied(name); ok {
 			return ok

Var.go

@@ -21,7 +21,7 @@ import (
 type Var[V any] struct {
 	// ID is the testCase spec variable group from where the cached value can be accessed later on.
 	// ID is Mandatory when you create a variable, else the empty string will be used as the variable group.
-	ID string
+	ID VarID
 	// Init is an optional constructor definition that will be used when Var is bonded to a *Spec without constructor function passed to the Let function.
 	// The goal of this field to initialize a variable that can be reused across different testing suites by bounding the Var to a given testing suite.
 	//
@@ -47,17 +47,19 @@ type Var[V any] struct {
 	Deps Vars
 }
 
+type VarID string
+
 type Vars []tetcaseVar
 
 type tetcaseVar interface {
 	isTestcaseVar()
-	id() string
+	id() VarID
 	get(t *T) any
 	bind(s *Spec)
 }
 
 func (Var[V]) isTestcaseVar() {}
-func (v Var[V]) id() string   { return v.ID }
+func (v Var[V]) id() VarID    { return v.ID }
 
 type VarInit[V any] func(*T) V
 

Var_test.go

@@ -24,12 +24,12 @@ func TestVar(t *testing.T) {
 	// This should not be the case for anything else outside the testing framework.
 	s.HasSideEffect()
 	rnd := random.New(random.CryptoSeed{})
-	var testVar = testcase.Var[int]{ID: rnd.StringNWithCharset(5, "abcdefghijklmnopqrstuvwxyz")}
+	var testVar = testcase.Var[int]{ID: testcase.VarID(rnd.StringNWithCharset(5, "abcdefghijklmnopqrstuvwxyz"))}
 	expected := rnd.Int()
 
 	stub := &doubles.TB{}
 	willFatal := willFatalWithMessageFn(stub)
-	willFatalWithVariableNotFoundMessage := func(s *testcase.Spec, tb testing.TB, varName string, blk func(*testcase.T)) {
+	willFatalWithVariableNotFoundMessage := func(s *testcase.Spec, tb testing.TB, varName testcase.VarID, blk func(*testcase.T)) {
 		tct := testcase.NewTWithSpec(stub, s)
 		assert.Must(tb).Contain(willFatal(t, func() { blk(tct) }),
 			fmt.Sprintf("Variable %q is not found.", varName))
@@ -207,7 +207,7 @@ func TestVar(t *testing.T) {
 		})
 	})
 
-	willFatalWithOnLetMissing := func(s *testcase.Spec, tb testing.TB, varName string, blk func(*testcase.T)) {
+	willFatalWithOnLetMissing := func(s *testcase.Spec, tb testing.TB, varName testcase.VarID, blk func(*testcase.T)) {
 		tct := testcase.NewTWithSpec(stub, s)
 		assert.Must(tb).Contain(willFatal(t, func() { blk(tct) }),
 			fmt.Sprintf("%s Var has Var.OnLet. You must use Var.Let, Var.LetValue to initialize it properly.", varName))

backward.go

@@ -7,7 +7,7 @@ import "go.llib.dev/testcase/assert"
 // thus Let has moved to be a pkg-level function in the package.
 //
 // DEPRECATED: use testcase.Let instead testcase#Spec.Let.
-func (spec *Spec) Let(varName string, blk VarInit[any]) Var[any] {
+func (spec *Spec) Let(varName VarID, blk VarInit[any]) Var[any] {
 	return let[any](spec, varName, blk)
 }
 
@@ -16,7 +16,7 @@ func (spec *Spec) Let(varName string, blk VarInit[any]) Var[any] {
 // thus LetValue has moved to be a pkg-level function in the package.
 //
 // DEPRECATED: use testcase.LetValue instead testcase#Spec.LetValue.
-func (spec *Spec) LetValue(varName string, value any) Var[any] {
+func (spec *Spec) LetValue(varName VarID, value any) Var[any] {
 	return letValue[any](spec, varName, value)
 }
 

docs/contracts.md

@@ -86,8 +86,8 @@ type RoleInterfaceContract struct {
 
 type RoleInterfaceContractSubject interface {
    mypkg.RoleInterfaceName
-   FindByID(ctx context.Context, id string) (mypkg.XY, bool, error)
-   DeleteByID(ctx context.Context, id string) error
+   FindByID(ctx context.Context, id VarID) (mypkg.XY, bool, error)
+   DeleteByID(ctx context.Context, id VarID) error
 }
 ```
 

let.go

@@ -93,7 +93,7 @@ func LetValue[V any](spec *Spec, value V) Var[V] {
 	return letValue[V](spec, makeVarID(spec), value)
 }
 
-func let[V any](spec *Spec, varID string, blk VarInit[V]) Var[V] {
+func let[V any](spec *Spec, varID VarID, blk VarInit[V]) Var[V] {
 	helper(spec.testingTB).Helper()
 	if spec.immutable {
 		spec.testingTB.Fatalf(warnEventOnImmutableFormat, `Let`)
@@ -108,7 +108,7 @@ func let[V any](spec *Spec, varID string, blk VarInit[V]) Var[V] {
 	return Var[V]{ID: varID, Init: blk}
 }
 
-func letValue[V any](spec *Spec, varName string, value V) Var[V] {
+func letValue[V any](spec *Spec, varName VarID, value V) Var[V] {
 	helper(spec.testingTB).Helper()
 	if reflects.IsMutable(value) {
 		spec.testingTB.Fatalf(panicMessageForLetValue, value)
@@ -121,7 +121,7 @@ func letValue[V any](spec *Spec, varName string, value V) Var[V] {
 }
 
 // latest decl is the first and the deeper you want to reach back, the higher the index
-func findCurrentDeclsFor(spec *Spec, varName string) []variablesInitBlock {
+func findCurrentDeclsFor(spec *Spec, varName VarID) []variablesInitBlock {
 	var decls []variablesInitBlock
 	for _, s := range spec.specsFromCurrent() {
 		if decl, ok := s.vars.defs[varName]; ok {
@@ -131,13 +131,13 @@ func findCurrentDeclsFor(spec *Spec, varName string) []variablesInitBlock {
 	return decls
 }
 
-func makeVarID(spec *Spec) string {
+func makeVarID(spec *Spec) VarID {
 	helper(spec.testingTB).Helper()
 	location := caller.GetLocation(false)
 	// when variable is declared within a loop
 	// providing a variable ID offset is required to identify the variable uniquely.
 
-	varIDIndex := make(map[string]struct{})
+	varIDIndex := make(map[VarID]struct{})
 	for _, s := range spec.specsFromParent() {
 		for k := range s.vars.locks {
 			varIDIndex[k] = struct{}{}
@@ -154,19 +154,19 @@ func makeVarID(spec *Spec) string {
 	}
 
 	var (
-		id     string
+		id     VarID
 		offset int
 	)
 positioning:
 	for {
 		// quick path for the majority of the case.
-		if _, ok := varIDIndex[location]; !ok {
-			id = location
+		if _, ok := varIDIndex[VarID(location)]; !ok {
+			id = VarID(location)
 			break positioning
 		}
 
 		offset++
-		id = fmt.Sprintf("%s#[%d]", location, offset)
+		id = VarID(fmt.Sprintf("%s#[%d]", location, offset))
 		if _, ok := varIDIndex[id]; !ok {
 			break positioning
 		}

let/let.go

@@ -39,7 +39,7 @@ func As[To, From any](Var testcase.Var[From]) testcase.Var[To] {
 		panic(fmt.Sprintf("you can't have %s as %s", fromType.String(), toType.String()))
 	}
 	return testcase.Var[To]{
-		ID: fmt.Sprintf("%s AS %T #%d", Var.ID, *new(To), asID),
+		ID: testcase.VarID(fmt.Sprintf("%s AS %T #%d", Var.ID, *new(To), asID)),
 		Init: func(t *testcase.T) To {
 			var rFrom = reflect.ValueOf(Var.Get(t))
 			return rFrom.Convert(toType).Interface().(To)

let_test.go

@@ -203,7 +203,7 @@ func TestLet_letVarIDInNonCoreTestcasePackage(t *testing.T) {
 
 	s := testcase.NewSpec(t)
 	resp := httpspec.LetResponseRecorder(s)
-	t.Logf(resp.ID)
+	t.Logf("id: %s", resp.ID)
 	assert.NotContain(t, resp.ID, "_test.go")
 	assert.NotContain(t, resp.ID, filepath.Base(frame.File))
 	assert.Contain(t, resp.ID, filepath.Dir(frame.File))