feat(vars): add interactive prompting for required variables (#2579)

executor.go

@@ -44,6 +44,7 @@ type (
 		DisableFuzzy        bool
 		AssumeYes           bool
 		AssumeTerm          bool // Used for testing
+		Interactive         bool
 		Dry                 bool
 		Summary             bool
 		Parallel            bool
@@ -70,6 +71,7 @@ type (
 		fuzzyModel     *fuzzy.Model
 		fuzzyModelOnce sync.Once
 
+		promptedVars         *ast.Vars // vars collected via interactive prompts
 		concurrencySemaphore chan struct{}
 		taskCallCount        map[string]*int32
 		mkdirMutexMap        map[string]*sync.Mutex
@@ -367,6 +369,19 @@ func (o *assumeTermOption) ApplyToExecutor(e *Executor) {
 	e.AssumeTerm = o.assumeTerm
 }
 
+// WithInteractive tells the [Executor] to prompt for missing required variables.
+func WithInteractive(interactive bool) ExecutorOption {
+	return &interactiveOption{interactive}
+}
+
+type interactiveOption struct {
+	interactive bool
+}
+
+func (o *interactiveOption) ApplyToExecutor(e *Executor) {
+	e.Interactive = o.interactive
+}
+
 // WithDry tells the [Executor] to output the commands that would be run without
 // actually running them.
 func WithDry(dry bool) ExecutorOption {