Support loading via http.FileSystem

[hottestseason]

It is great if this library can load with http.FileSystem because we can embed specification files into single binary with Go1.16's embed feature

package main

import (
	"embed"
	"log"
	"net/http"

	"github.com/getkin/kin-openapi/openapi3"
)

//go:embed spec/*
var spec embed.FS

func main() {
	loader := openapi3.NewSwaggerLoader()
	loader.IsExternalRefsAllowed = true

	swagger, err := loader.LoadSwaggerFromFileSystem(http.FS(spec), "spec/openapi.yml")
	if err != nil {
		panic(err)
	}

	log.Printf("%s\n", swagger.Paths["/foo"].Get.Responses["200"].Value.Content["application/json"].Schema.Value.Properties["foo"].Value.Type)
}

openapi: "3.0.0"
info:
  version: "1.0"
  title: example
paths:
  /foo:
    $ref: ./paths/foo.yml

get:
  parameters:
  responses:
    "200":
      description: OK
      content:
        application/json:
          schema:
            type: object
            properties:
              foo:
                type: string
                example: foo

[fenollp]

Is this not doable today with a LoadSwaggerFromURIFunc?

[hottestseason]

Unfortunately it doesn't works.

package main

import (
	"context"
	"embed"
	"fmt"
	"net/url"
	"path/filepath"

	"github.com/getkin/kin-openapi/openapi3"
)

//go:embed spec/*
var spec embed.FS

func main() {
	ctx := context.Background()

	loader := openapi3.NewSwaggerLoader()
	loader.IsExternalRefsAllowed = true
	loader.LoadSwaggerFromURIFunc = func(loader *openapi3.SwaggerLoader, url *url.URL) (*openapi3.Swagger, error) {
		data, err := spec.ReadFile(filepath.Join("spec", url.Path))
		if err != nil {
			panic(err)
		}
		swagger, err := loader.LoadSwaggerFromData(data)
		if err != nil {
			panic(err)
		}
		return swagger, nil
	}
	swagger, err := loader.LoadSwaggerFromFile("openapi.yml")
	if err != nil {
		panic(err)
	}

	fmt.Printf("%+v\n", swagger.Paths["/foo"].Get.Responses["200"].Value.Content["application/json"].Schema)

	if err = swagger.Validate(ctx); err != nil {
		panic(err)
	}
}

% go run main.go
panic: open ./components/Bar.yml: no such file or directory

goroutine 1 [running]:
main.main.func1(0xc0001a09a0, 0xc0000ba240, 0x30, 0x139c680, 0x1)
	/Users/sumihiko.natsu/src/github.com/hottestseason/kin-openapi/main.go:28 +0x137
github.com/getkin/kin-openapi/openapi3.(*SwaggerLoader).loadSwaggerFromFileInternal(0xc0001a09a0, 0x13b5305, 0xb, 0x13a1a40, 0xc000052701, 0xc0001a09a0)
	/Users/sumihiko.natsu/src/github.com/hottestseason/kin-openapi/openapi3/swagger_loader.go:143 +0x131
github.com/getkin/kin-openapi/openapi3.(*SwaggerLoader).LoadSwaggerFromFile(0xc0001a09a0, 0x13b5305, 0xb, 0xc000000180, 0x200000003, 0xc000000180)
	/Users/sumihiko.natsu/src/github.com/hottestseason/kin-openapi/openapi3/swagger_loader.go:136 +0x78
main.main()
	/Users/sumihiko.natsu/src/github.com/hottestseason/kin-openapi/main.go:32 +0x6f
exit status 2

It looks LoadSwaggerFromURIFunc is only used while loading the root OpenAPI spec file, but when resolving references ioutil.ReadFile will be used.

kin-openapi/openapi3/swagger_loader.go

Line 126 in 89012b7

data, err := ioutil.ReadFile(location.Path)

[fenollp]

Then

kin-openapi/openapi3/swagger_loader.go

Line 126 in 89012b7

data, err := ioutil.ReadFile(location.Path)

needs to use the func and be passed swaggerLoader :)
Could you update your PR to do this change and provide an example func that uses http.FS?

[fenollp]

Doing this actually also solves #231

[hottestseason]

OK, I'll try.
Thanks for your advice!!

[hottestseason]

I prepared another PR #316

package main

import (
	"context"
	"embed"
	"fmt"
	"github.com/getkin/kin-openapi/openapi3"
	"net/url"
)

//go:embed spec/*
var spec embed.FS

func main() {
	ctx := context.Background()

	loader := openapi3.NewSwaggerLoader()
	loader.IsExternalRefsAllowed = true
	loader.ReadFromURIFunc = func(loader *openapi3.SwaggerLoader, url *url.URL) ([]byte, error) {
		fmt.Println(url.Path)
		return spec.ReadFile(url.Path)
	}
	swagger, err := loader.LoadSwaggerFromFile("spec/openapi.yml")
	if err != nil {
		panic(err)
	}

	if err = swagger.Validate(ctx); err != nil {
		panic(err)
	}

	fmt.Printf("%+v\n", swagger.Paths["/foo"].Get.Responses["200"].Value.Content["application/json"].Schema.Value)
}

% go run main.go
spec/openapi.yml
spec/components/Bar.yml
spec/components/Foo.yml
spec/openapi.yml
spec/components/Bar.yml
spec/paths/foo.yml
spec/openapi.yml
spec/components/Foo.yml
spec/openapi.yml
&{ExtensionProps:{Extensions:map[]} OneOf:[] AnyOf:[] AllOf:[] Not:<nil> Type:object Title: Format: Description: Enum:[] Default:<nil> Example:<nil> ExternalDocs:<nil> AdditionalPropertiesAllowed:<nil> UniqueItems:false ExclusiveMin:false ExclusiveMax:false Nullable:false ReadOnly:false WriteOnly:false AllowEmptyValue:false XML:<nil> Deprecated:false Min:<nil> Max:<nil> MultipleOf:<nil> MinLength:0 MaxLength:<nil> Pattern: compiledPattern:<nil> MinItems:0 MaxItems:<nil> Items:<nil> Required:[] Properties:map[foo:0xc00000ee40] MinProps:0 MaxProps:<nil> AdditionalProperties:<nil> Discriminator:<nil>}

[fenollp]

Very nice, thank you! I like this a lot.
I'll merge your PR and in a next PR I'll get rid of the old Func which does not bring anything from the uses I can see.
Also I'll look into adding your snippet above as an example/test.