Add command validate to check for parse errors

[apoorvam]

Adds a command validate to check for parse errors #31 #55

Running command dunner validate will check for any parse errors and warnings. If there are any errors, it fails the cmd. If not it finishes by listing any warnings if present.

Example:

$ dunner validate
ERRO[2019-03-22 17:15:56] dunner: [stats] Image repository name cannot be empty

Please let me know if there are any other validations for configs to be included.

[ayushjn20]

Superb work!
You could have added some more validations, which in my opinion, are important ones like,

• Directories listed for mounting on containers are present on host or not.
• Task is present or not when called as @taskName in a step of some other task.
• Sufficient number of arguments passed when one task is used as step for another task.

[apoorvam]

@ayushjn20 You're right, We need to look for all kind of other validations. I'll try add the ones you suggested.

[agentmilindu]

Is there something similar to Joi for Golang?

[agentmilindu]

Can we use https://github.com/go-playground/validator?

See https://github.com/go-playground/validator/blob/v9/_examples/simple/main.go

[apoorvam]

I gave a shot at the go-playground/validator package. This is how it would look:

type Task struct {
	Name    string   `yaml:"name"`
	Image   string   `yaml:"image" validate:"required"`
	SubDir  string   `yaml:"dir"`
	Command []string `yaml:"command" validate:"required,gt=0,dive,required"`
	Envs    []string `yaml:"envs"`
	Mounts  []string `yaml:"mounts"`
	Args    []string `yaml:"args"`
}

type Configs struct {
	Tasks map[string][]Task `validate:"required,gt=0,dive,keys,required,endkeys,required,gt=0,dive,required"`
}

func (configs *Configs) Validate() ([]error) {
	var errs []error
	err := validator.New().Struct(configs)
	if (err != nil) {
		if _, ok := err.(*validator.InvalidValidationError); ok {
			errs = append(errs, err)
		} else {
			for _, e := range err.(validator.ValidationErrors) {
				errs = append(errs, fmt.Errorf("dunner: Validation for field '%s' failed on %s tag", e.Field(), e.Tag()))
			}
		}
	}
	return errs
}

• I think it can get complicated and requires to understand the DSL defined by library.
• We cannot differentiate warnings and errors.
• Error messages are not easy to be made user-friendly. The above code would give an error message like: dunner: Validation for field 'Command' failed on gt tag
  To give more appropriate error message, we'll have to use translations like this: https://github.com/Aptomi/k8s-app-engine/blob/master/pkg/lang/validation.go#L98

Advantage is that messages can be uniform and easy to add more validations. I'll dig up more on if its worth it or probably write a custom validator.
@agentmilindu / all, Let me know if you have any thoughts on this.

[agentmilindu]

@apoorvam

1. https://www.slideshare.net/surajssd009005/jsonschema-with-golang
2. https://stackoverflow.com/a/53230568/1190184

[apoorvam]

Update:

• dunner validate checks for any parse errors and validation errors. If there are any, it fails with non-zero exit code.
• Same validation is performed before dunner do <task> also.
• If any required fields are missing/empty, it gives error as below. It prefixes each error with task name so its easy to track error.

task 'stats': image is a required field

• In case of mount dir, it fails if its not in right format. Or if directory is not present in the host machine.

$ dunner validate
Validation failed for following errors:
task 'test': mount directory '/tmp/sample:/tmp' is invalid. Check format is '<valid_src_dir>:<valid_dest_dir>:<mode>' and has right permission level

• Added framework for add custom validations along with required context info.

Task is present or not when called as @taskName in a step of some other task.
Sufficient number of arguments passed when one task is used as step for another task.

Above two validations should be added after this change to use follow is implemented. Else it is just redundant. Will make it a part of new issue.

@agentmilindu @ayushjn20 Please review.