Plugins: Fs: Add option to access unallowed files in dev mode (#66492)

* Plugins: Fs: Add option to access unallowed files in dev mode

* Plugins: Fs: allow accessing unallowed files only when in dev mode

* Plugins: Fs: Add ProvideLocalFinder

* Plugins: FS: Pass whole config in NewLocalFinder()

* Plugins: FS: Add AllowListLocalFS

* Plugins: FS: Fix some tests

* Plugins: FS: Update tests

* Plugins: FS: Removed dead code

* Plugins: FS: Add tests for AllowListFS

* Plugins: FS: Update comments

* Plugins: FS: Use variadic arguments for allow list rather than map

* Plugins: FS: Remove unnecessary log

* Plugins: FS: Do not escape plugin root dir

* Fix merge conflict

* Plugins: FS: Update comments

* Plugins: FS: PR review changes

* Fix merge conflict

* Fix tests

* Cleanup

* Fix flaky test

* Changes from PR review

* Lint

* Add comment to LocalFS.Remove

* Fix Windows

* Renamed devMode to production

pkg/plugins/test_utils.go

@@ -0,0 +1,82 @@
+package plugins
+
+import (
+	"bytes"
+	"io/fs"
+	"os"
+	"time"
+)
+
+var (
+	_ FS          = &inMemoryFS{}
+	_ fs.File     = &inMemoryFile{}
+	_ fs.FileInfo = &inMemoryFileInfo{}
+)
+
+// inMemoryFS is an FS that stores files in-memory.
+type inMemoryFS struct {
+	files map[string][]byte
+}
+
+// NewInMemoryFS returns a new FS with the specified files and content.
+// The provided value is a map from file name (keys) to file content (values).
+func NewInMemoryFS(files map[string][]byte) FS {
+	return &inMemoryFS{files: files}
+}
+
+func (f inMemoryFS) Base() string {
+	return ""
+}
+
+func (f inMemoryFS) Files() ([]string, error) {
+	fps := make([]string, 0, len(f.files))
+	for fn := range f.files {
+		fps = append(fps, fn)
+	}
+	return fps, nil
+}
+
+func (f inMemoryFS) Open(fn string) (fs.File, error) {
+	if _, ok := f.files[fn]; !ok {
+		return nil, ErrFileNotExist
+	}
+	return &inMemoryFile{path: fn, reader: bytes.NewReader(f.files[fn])}, nil
+}
+
+// NewFakeFS returns a new FS that always returns ErrFileNotExist when trying to Open() and empty Files().
+func NewFakeFS() FS {
+	return NewInMemoryFS(nil)
+}
+
+// inMemoryFile is a fs.File whose content is stored in memory.
+type inMemoryFile struct {
+	path   string
+	reader *bytes.Reader
+}
+
+func (f *inMemoryFile) Stat() (fs.FileInfo, error) {
+	return inMemoryFileInfo{
+		name: f.path,
+		size: f.reader.Size(),
+	}, nil
+}
+
+func (f *inMemoryFile) Read(b []byte) (int, error) {
+	return f.reader.Read(b)
+}
+
+func (f *inMemoryFile) Close() error {
+	return nil
+}
+
+type inMemoryFileInfo struct {
+	name string
+	size int64
+}
+
+func (f inMemoryFileInfo) Name() string       { return f.name }
+func (f inMemoryFileInfo) Size() int64        { return f.size }
+func (f inMemoryFileInfo) Mode() os.FileMode  { return 0444 } // Read for all
+func (f inMemoryFileInfo) ModTime() time.Time { return time.Time{} }
+func (f inMemoryFileInfo) IsDir() bool        { return false }
+func (f inMemoryFileInfo) Sys() interface{}   { return nil }