fix: special variable type errors in vars with no task context (#2107)

* fix: stop dotenv trying to fetch variables when no dotenv specified

* fix: set special variables to "" when they can't be calculated

compiler.go

@@ -209,9 +209,16 @@ func (c *Compiler) getSpecialVars(t *ast.Task, call *Call) (map[string]string, e
 		allVars["TASK_DIR"] = filepathext.SmartJoin(c.Dir, t.Dir)
 		allVars["TASKFILE"] = t.Location.Taskfile
 		allVars["TASKFILE_DIR"] = filepath.Dir(t.Location.Taskfile)
+	} else {
+		allVars["TASK"] = ""
+		allVars["TASK_DIR"] = ""
+		allVars["TASKFILE"] = ""
+		allVars["TASKFILE_DIR"] = ""
 	}
 	if call != nil {
 		allVars["ALIAS"] = call.Task
+	} else {
+		allVars["ALIAS"] = ""
 	}
 
 	return allVars, nil

setup.go

@@ -209,6 +209,10 @@ func (e *Executor) setupCompiler() error {
 }
 
 func (e *Executor) readDotEnvFiles() error {
+	if e.Taskfile == nil || len(e.Taskfile.Dotenv) == 0 {
+		return nil
+	}
+
 	if e.Taskfile.Version.LessThan(ast.V3) {
 		return nil
 	}

taskfile/dotenv.go

@@ -12,10 +12,6 @@ import (
 )
 
 func Dotenv(vars *ast.Vars, tf *ast.Taskfile, dir string) (*ast.Vars, error) {
-	if len(tf.Dotenv) == 0 {
-		return nil, nil
-	}
-
 	env := ast.NewVars()
 	cache := &templater.Cache{Vars: vars}