feat: option to ensure variable is within the list of values (#1827)

errors/errors.go

@@ -32,6 +32,7 @@ const (
 	CodeTaskCalledTooManyTimes
 	CodeTaskCancelled
 	CodeTaskMissingRequiredVars
+	CodeTaskNotAllowedVars
 )
 
 // TaskError extends the standard error interface with a Code method. This code will

errors/errors_task.go

@@ -158,3 +158,29 @@ func (err *TaskMissingRequiredVars) Error() string {
 func (err *TaskMissingRequiredVars) Code() int {
 	return CodeTaskMissingRequiredVars
 }
+
+type NotAllowedVar struct {
+	Value string
+	Enum  []string
+	Name  string
+}
+
+type TaskNotAllowedVars struct {
+	TaskName       string
+	NotAllowedVars []NotAllowedVar
+}
+
+func (err *TaskNotAllowedVars) Error() string {
+	var builder strings.Builder
+
+	builder.WriteString(fmt.Sprintf("task: Task %q cancelled because it is missing required variables:\n", err.TaskName))
+	for _, s := range err.NotAllowedVars {
+		builder.WriteString(fmt.Sprintf("  - %s has an invalid value : '%s' (allowed values : %v)\n", s.Name, s.Value, s.Enum))
+	}
+
+	return builder.String()
+}
+
+func (err *TaskNotAllowedVars) Code() int {
+	return CodeTaskNotAllowedVars
+}

requires.go

@@ -1,6 +1,8 @@
 package task
 
 import (
+	"slices"
+
 	"github.com/go-task/task/v3/errors"
 	"github.com/go-task/task/v3/taskfile/ast"
 )
@@ -16,9 +18,19 @@ func (e *Executor) areTaskRequiredVarsSet(t *ast.Task, call *ast.Call) error {
 	}
 
 	var missingVars []string
+	var notAllowedValuesVars []errors.NotAllowedVar
 	for _, requiredVar := range t.Requires.Vars {
-		if !vars.Exists(requiredVar) {
-			missingVars = append(missingVars, requiredVar)
+		value, isString := vars.Get(requiredVar.Name).Value.(string)
+		if !vars.Exists(requiredVar.Name) {
+			missingVars = append(missingVars, requiredVar.Name)
+		} else {
+			if isString && requiredVar.Enum != nil && !slices.Contains(requiredVar.Enum, value) {
+				notAllowedValuesVars = append(notAllowedValuesVars, errors.NotAllowedVar{
+					Value: value,
+					Enum:  requiredVar.Enum,
+					Name:  requiredVar.Name,
+				})
+			}
 		}
 	}
 
@@ -29,5 +41,12 @@ func (e *Executor) areTaskRequiredVarsSet(t *ast.Task, call *ast.Call) error {
 		}
 	}
 
+	if len(notAllowedValuesVars) > 0 {
+		return &errors.TaskNotAllowedVars{
+			TaskName:       t.Name(),
+			NotAllowedVars: notAllowedValuesVars,
+		}
+	}
+
 	return nil
 }

task_test.go

@@ -155,6 +155,39 @@ func TestVars(t *testing.T) {
 	tt.Run(t)
 }
 
+func TestRequires(t *testing.T) {
+	const dir = "testdata/requires"
+
+	var buff bytes.Buffer
+	e := &task.Executor{
+		Dir:    dir,
+		Stdout: &buff,
+		Stderr: &buff,
+	}
+
+	require.NoError(t, e.Setup())
+	require.ErrorContains(t, e.Run(context.Background(), &ast.Call{Task: "missing-var"}), "task: Task \"missing-var\" cancelled because it is missing required variables: foo")
+	buff.Reset()
+	require.NoError(t, e.Setup())
+
+	vars := &ast.Vars{}
+	vars.Set("foo", ast.Var{Value: "bar"})
+	require.NoError(t, e.Run(context.Background(), &ast.Call{
+		Task: "missing-var",
+		Vars: vars,
+	}))
+	buff.Reset()
+
+	require.NoError(t, e.Setup())
+	require.ErrorContains(t, e.Run(context.Background(), &ast.Call{Task: "validation-var", Vars: vars}), "task: Task \"validation-var\" cancelled because it is missing required variables:\n  - foo has an invalid value : 'bar' (allowed values : [one two])")
+	buff.Reset()
+
+	require.NoError(t, e.Setup())
+	vars.Set("foo", ast.Var{Value: "one"})
+	require.NoError(t, e.Run(context.Background(), &ast.Call{Task: "validation-var", Vars: vars}))
+	buff.Reset()
+}
+
 func TestSpecialVars(t *testing.T) {
 	const dir = "testdata/special_vars"
 	const subdir = "testdata/special_vars/subdir"

taskfile/ast/requires.go

@@ -1,10 +1,15 @@
 package ast
 
-import "github.com/go-task/task/v3/internal/deepcopy"
+import (
+	"gopkg.in/yaml.v3"
+
+	"github.com/go-task/task/v3/errors"
+	"github.com/go-task/task/v3/internal/deepcopy"
+)
 
 // Requires represents a set of required variables necessary for a task to run
 type Requires struct {
-	Vars []string
+	Vars []*VarsWithValidation
 }
 
 func (r *Requires) DeepCopy() *Requires {
@@ -16,3 +21,47 @@ func (r *Requires) DeepCopy() *Requires {
 		Vars: deepcopy.Slice(r.Vars),
 	}
 }
+
+type VarsWithValidation struct {
+	Name string
+	Enum []string
+}
+
+func (v *VarsWithValidation) DeepCopy() *VarsWithValidation {
+	if v == nil {
+		return nil
+	}
+	return &VarsWithValidation{
+		Name: v.Name,
+		Enum: v.Enum,
+	}
+}
+
+// UnmarshalYAML implements yaml.Unmarshaler interface.
+func (v *VarsWithValidation) UnmarshalYAML(node *yaml.Node) error {
+	switch node.Kind {
+
+	case yaml.ScalarNode:
+		var cmd string
+		if err := node.Decode(&cmd); err != nil {
+			return errors.NewTaskfileDecodeError(err, node)
+		}
+		v.Name = cmd
+		v.Enum = nil
+		return nil
+
+	case yaml.MappingNode:
+		var vv struct {
+			Name string
+			Enum []string
+		}
+		if err := node.Decode(&vv); err != nil {
+			return errors.NewTaskfileDecodeError(err, node)
+		}
+		v.Name = vv.Name
+		v.Enum = vv.Enum
+		return nil
+	}
+
+	return errors.NewTaskfileDecodeError(nil, node).WithTypeMessage("requires")
+}

testdata/requires/Taskfile.yml

@@ -0,0 +1,18 @@
+version: '3'
+
+tasks:
+  default:
+    - task: missing-var
+
+  missing-var:
+    requires:
+      vars:
+        - foo
+    cmd: echo "{{.foo}}"
+
+
+  validation-var:
+    requires:
+      vars:
+        - name: foo
+          enum: ['one', 'two']

website/docs/reference/cli.mdx

@@ -63,7 +63,7 @@ four groups with the following ranges:
 A full list of the exit codes and their descriptions can be found below:
 
 | Code | Description                                                         |
-| ---- | ------------------------------------------------------------ |
+|------|---------------------------------------------------------------------|
 | 0    | Success                                                             |
 | 1    | An unknown error occurred                                           |
 | 100  | No Taskfile was found                                               |
@@ -81,6 +81,7 @@ A full list of the exit codes and their descriptions can be found below:
 | 204  | A task was called too many times                                    |
 | 205  | A task was cancelled by the user                                    |
 | 206  | A task was not executed due to missing required variables           |
+| 207  | A task was not executed due to a variable having an incorrect value |
 
 These codes can also be found in the repository in
 [`errors/errors.go`](https://github.com/go-task/task/blob/main/errors/errors.go).

website/docs/usage.mdx

@@ -1060,6 +1060,40 @@ tasks:
       vars: [IMAGE_NAME, IMAGE_TAG]
 ```
 
+### Ensuring required variables have allowed values
+
+If you want to ensure that a variable is set to one of a predefined set of valid values before executing a task, you can use requires.
+This is particularly useful when there are strict requirements for what values a variable can take, and you want to provide clear feedback to the user when an invalid value is detected.
+
+To use `requires`, you specify an array of allowed values in the vars sub-section under requires. Task will check if the variable is set to one of the allowed values.
+If the variable does not match any of these values, the task will raise an error and stop execution.
+
+This check applies both to user-defined variables and environment variables.
+
+Example of using `requires`:
+
+```yaml
+version: '3'
+
+tasks:
+  deploy:
+    cmds:
+      - echo "deploying to {{.ENV}}"
+
+    requires:
+      vars:
+        - name: ENV
+          enum: [dev, beta, prod]
+```
+
+If `ENV` is not one of 'dev', 'beta' or 'prod' an error will be raised.
+
+:::note
+
+This is supported only for string variables.
+
+:::
+
 ## Variables
 
 Task allows you to set variables using the `vars` keyword. The following

website/static/schema.json

@@ -558,7 +558,19 @@
           "description": "List of variables that must be defined for the task to run",
           "type": "array",
           "items": {
-            "type": "string"
+            "oneOf": [
+              { "type": "string" },
+              {
+                "type": "object",
+                "properties": {
+                  "name": { "type": "string" },
+                  "enum": { "type": "array",
+                    "items": { "type": "string" } }
+                },
+                "required": ["name", "enum"],
+                "additionalProperties": false
+              }
+            ]
           }
         }
       },