openapi: Make file client more easy to re-use

A few notes about the change:
1. I need to initialize the fileclient once, in an init function, so I
don't have access to `testing.T` yet.
2. I want to be able to configure the openapi files that I use
3. We already have a "cache" client that wraps another client, we don't
need to re-implement caching here, one can just do:
`cache.NewClient(openapitest.NewFileClient("some/path"))` to do a cached
client. Or initialize it in an init/global var.

Since there is still some value to use the embedded file, make an
alternative constructor while using fs.FS interface to be able to
manipulate both virtual and disk-based filesystems.

Kubernetes-commit: 29503fd8d45bc2c9438e92936bf4111162529b40

openapi/openapitest/fileclient.go

@@ -19,33 +19,35 @@ package openapitest
 import (
 	"embed"
 	"errors"
-	"path/filepath"
+	"io/fs"
+	"os"
 	"strings"
-	"sync"
-	"testing"
 
 	"k8s.io/client-go/openapi"
 )
 
 //go:embed testdata/*_openapi.json
-var f embed.FS
+var embedded embed.FS
 
 // NewFileClient returns a test client implementing the openapi.Client
-// interface, which serves a subset of hard-coded GroupVersion
-// Open API V3 specifications files. The subset of specifications is
-// located in the "testdata" subdirectory.
-func NewFileClient(t *testing.T) openapi.Client {
-	if t == nil {
-		panic("non-nil testing.T required; this package is only for use in tests")
+// interface, which serves Open API V3 specifications files from the
+// given path, as prepared in `api/openapi-spec/v3`.
+func NewFileClient(path string) openapi.Client {
+	return &fileClient{f: os.DirFS(path)}
+}
+
+// NewEmbeddedFileClient returns a test client that uses the embedded
+// `testdata` openapi files.
+func NewEmbeddedFileClient() openapi.Client {
+	f, err := fs.Sub(embedded, "testdata")
+	if err != nil {
+		panic(err)
 	}
-	return &fileClient{t: t}
+	return &fileClient{f: f}
 }
 
 type fileClient struct {
-	t     *testing.T
-	init  sync.Once
-	paths map[string]openapi.GroupVersion
-	err   error
+	f fs.FS
 }
 
 // fileClient implements the openapi.Client interface.
@@ -60,29 +62,23 @@ var _ openapi.Client = &fileClient{}
 //
 // The file contents are read only once. All files must parse correctly
 // into an api path, or an error is returned.
-func (t *fileClient) Paths() (map[string]openapi.GroupVersion, error) {
-	t.init.Do(func() {
-		t.paths = map[string]openapi.GroupVersion{}
-		entries, err := f.ReadDir("testdata")
-		if err != nil {
-			t.err = err
-			t.t.Error(err)
-		}
-		for _, e := range entries {
-			// this reverses the transformation done in hack/update-openapi-spec.sh
-			path := strings.ReplaceAll(strings.TrimSuffix(e.Name(), "_openapi.json"), "__", "/")
-			t.paths[path] = &fileGroupVersion{t: t.t, filename: filepath.Join("testdata", e.Name())}
-		}
-	})
-	return t.paths, t.err
+func (f *fileClient) Paths() (map[string]openapi.GroupVersion, error) {
+	paths := map[string]openapi.GroupVersion{}
+	entries, err := fs.ReadDir(f.f, ".")
+	if err != nil {
+		return nil, err
+	}
+	for _, e := range entries {
+		// this reverses the transformation done in hack/update-openapi-spec.sh
+		path := strings.ReplaceAll(strings.TrimSuffix(e.Name(), "_openapi.json"), "__", "/")
+		paths[path] = &fileGroupVersion{f: f.f, filename: e.Name()}
+	}
+	return paths, nil
 }
 
 type fileGroupVersion struct {
-	t        *testing.T
-	init     sync.Once
+	f        fs.FS
 	filename string
-	data     []byte
-	err      error
 }
 
 // fileGroupVersion implements the openapi.GroupVersion interface.
@@ -91,17 +87,10 @@ var _ openapi.GroupVersion = &fileGroupVersion{}
 // Schema returns the OpenAPI V3 specification for the GroupVersion as
 // unstructured bytes, or an error if the contentType is not
 // "application/json" or there is an error reading the spec file. The
-// file is read only once. The embedded file is located in the "testdata"
-// subdirectory.
-func (t *fileGroupVersion) Schema(contentType string) ([]byte, error) {
+// file is read only once.
+func (f *fileGroupVersion) Schema(contentType string) ([]byte, error) {
 	if contentType != "application/json" {
 		return nil, errors.New("openapitest only supports 'application/json' contentType")
 	}
-	t.init.Do(func() {
-		t.data, t.err = f.ReadFile(t.filename)
-		if t.err != nil {
-			t.t.Error(t.err)
-		}
-	})
-	return t.data, t.err
+	return fs.ReadFile(f.f, f.filename)
 }