GoFlow

---

Parse Go types to JavaScript Flow types

Currently a WIP, but very usable. Please create an issue for any edge-cases.

Usecase:

A project that runs Go as the REST server and utilizes Flow (which is fantastic) to keep their types straight on the client side. A personal project of mine needed something like this and I'm able to fit this in to my makefile so each type-change and recompile on the server side results in an update in the API-specific types on the client-side, and the code that needs altered is noticeable, and predictable.

Features include:

• override json names
• override types
• ignore types entirely
• use 'strict' mode
• parse single files, or entire directories (recursively or not)

Useage:

1. go get github.com/natdm/goflow
2. go install
3. goflow -help to see useage

Custom Tags:

• flow:"custom_name.custom_type" will override the Go field type with a custom name amd/or type. Useful for JS Promises and Generators
• Use flow:".custom_type" to get a custom type with no name-change and flow:"custom_name" to just change the name

Comments:

Ignore Types

• Add // @flowignore to the bottom of any comment above a struct to not parse that to your types.

Make Exact

• Add // @strict to the bottom of any comment above a struct to parse the more strict flow object.

Caveats:

• Currently, embedded types are not working. Coming soon.
• Nested structs are parsed as Objects (but could be overridden by using the flow tag).
• error andtime.* are parsed as string
• Slices of pointers are removing the flow decoration, ?. You will not be able to check if null yet.

Example

Below is a small example. Navigate to the /testdata folder to see a full file parsed to flow.

// Person has many types and should all convert correctly
type Person struct {
	Name             string    `json:"name"` // This is a name comment
	Age              int       `json:"age"`
	StringOverride   string    `json:"string_override" flow:"StringOverride.String"` // Override `string` with `String`
	Age64            int64     `json:"age64"`
	FlowIsAwesome    bool      `json:"flow_is_awesome"`
	Ignore           string    `json:"-"`
	Nullable         *string   `json:"nullable"`
	AnimalsArray     []Animal  `json:"animals_array"`       // I have no pointer
	AnimalsArrayPtr  *[]Animal `json:"animals_array_ptr"`   // I am a pointer
	AnimalsArrayPtr2 []*Animal `json:"animals_array_ptr_2"` // I hold pointers
	Payrate          Payrate   `json:"payrate"`
	HasComma         string    `json:"hascomma,omitempty"`
	HasParseTag      string    `json:"hasParseTag" flow:"some_generator.Generator"`
	HasLotsOfTags    string    `gorm:"column:first_name;index:fl_idx" json:"has_lots_of_tags"`
	InnerStruct      struct {
		Name  string `json:"name"`
		Age   int    `json:"age"`
		Child struct {
			Toys    []string `json:"toys"`
			Name    string   `json:"name" fname:"innername"`
			Friends struct {
				Name     string            `json:"name"`
				Age      int               `json:"age"`
				Buddies  map[string]Person `json:"buddies"`
				EmptyStr struct{}          `json:"empty_struct"`
			} `json:"friends"`
		} `json:"child"`
	} `json:"inner_struct"` // I have a comment in a nested struct
	Fn       func() string
	somedata string
	MapData  map[string]int `json:"map_data"`
}

to

// Person has many types and should all convert correctly
export type Person = {
	name: string,	//This is a name comment
	age: number,
	StringOverride: String,	//Override `string` with `String`
	age64: number,
	flow_is_awesome: boolean,
	nullable:  ?string,
	animals_array: Array<Animal>,	//I have no pointer
	animals_array_ptr:  ?Array<Animal>,	//I am a pointer
	animals_array_ptr_2: Array<Animal>,	//I hold pointers
	payrate: Payrate,
	hascomma: string,
	some_generator: Generator,
	has_lots_of_tags: string,
	inner_struct: Object,	//I have a comment in a nested struct
	map_data: { [key: string]: number },
}

TODO:

• Parse inline structs Done with some caveats, room for improvement
• Parse function types within structs (or ignore?) Done (ignoring things with no json tags)
• Ignore any commas in json tag Done
• Ignore anything not exported (structs and fields) Done
• Support type override with tag `flow:"SomeType"` Done
• Parse struct comments and carry over (leave as an optional flag) Done, no flag
• Parse struct comments for an ignore flag (// @flowignore) Done
• Allow flow exacts Done, use // @strict in comments
• Allow for primitives (String as well as the current string) Done - do it with ftype
• Speed up parsing of large files. 297 types and 817 fields take 30 seconds Done (cut time in half), but could always be better
• Don't blow up on unexported fields with json tags, although that shouldn't be a thing
• Parse embedded types Done
• Slices of pointers are removing pointer reference