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refactor: improve overlayFS errors #17808

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Merged
merged 4 commits into from
May 14, 2025
Merged

refactor: improve overlayFS errors #17808

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a1f2c0d
refactor: improve overlayFS errors
aslilac May 13, 2025
20263c6
revert calls
aslilac May 13, 2025
d4206d3
use the fs package functions rather than methods
aslilac May 13, 2025
fdd6a43
🧖‍♀️
aslilac May 13, 2025
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69 changes: 17 additions & 52 deletions coderd/files/overlay.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,15 +4,12 @@ import (
"io/fs"
"path"
"strings"

"golang.org/x/xerrors"
)

// overlayFS allows you to "join" together the template files tar file fs.FS
// with the Terraform modules tar file fs.FS. We could potentially turn this
// into something more parameterized/configurable, but the requirements here are
// a _bit_ odd, because every file in the modulesFS includes the
// .terraform/modules/ folder at the beginning of it's path.
// overlayFS allows you to "join" together multiple fs.FS. Files in any specific
// overlay will only be accessible if their path starts with the base path
// provided for the overlay. eg. An overlay at the path .terraform/modules
// should contain files with paths inside the .terraform/modules folder.
type overlayFS struct {
baseFS fs.FS
overlays []Overlay
Expand All @@ -23,64 +20,32 @@ type Overlay struct {
fs.FS
}

func NewOverlayFS(baseFS fs.FS, overlays []Overlay) (fs.FS, error) {
if err := valid(baseFS); err != nil {
return nil, xerrors.Errorf("baseFS: %w", err)
}

for _, overlay := range overlays {
if err := valid(overlay.FS); err != nil {
return nil, xerrors.Errorf("overlayFS: %w", err)
}
}

func NewOverlayFS(baseFS fs.FS, overlays []Overlay) fs.FS {
return overlayFS{
baseFS: baseFS,
overlays: overlays,
}, nil
}
}

func (f overlayFS) Open(p string) (fs.File, error) {
func (f overlayFS) target(p string) fs.FS {
target := f.baseFS
for _, overlay := range f.overlays {
if strings.HasPrefix(path.Clean(p), overlay.Path) {
return overlay.FS.Open(p)
target = overlay.FS
break
}
}
return f.baseFS.Open(p)
return target
}

func (f overlayFS) ReadDir(p string) ([]fs.DirEntry, error) {
for _, overlay := range f.overlays {
if strings.HasPrefix(path.Clean(p), overlay.Path) {
//nolint:forcetypeassert
return overlay.FS.(fs.ReadDirFS).ReadDir(p)
}
}
//nolint:forcetypeassert
return f.baseFS.(fs.ReadDirFS).ReadDir(p)
func (f overlayFS) Open(p string) (fs.File, error) {
return f.target(p).Open(p)
}

func (f overlayFS) ReadFile(p string) ([]byte, error) {
for _, overlay := range f.overlays {
if strings.HasPrefix(path.Clean(p), overlay.Path) {
//nolint:forcetypeassert
return overlay.FS.(fs.ReadFileFS).ReadFile(p)
}
}
//nolint:forcetypeassert
return f.baseFS.(fs.ReadFileFS).ReadFile(p)
func (f overlayFS) ReadDir(p string) ([]fs.DirEntry, error) {
return fs.ReadDir(f.target(p), p)
}

// valid checks that the fs.FS implements the required interfaces.
// The fs.FS interface is not sufficient.
func valid(fsys fs.FS) error {
_, ok := fsys.(fs.ReadDirFS)
if !ok {
return xerrors.New("overlayFS does not implement ReadDirFS")
}
_, ok = fsys.(fs.ReadFileFS)
if !ok {
return xerrors.New("overlayFS does not implement ReadFileFS")
}
return nil
func (f overlayFS) ReadFile(p string) ([]byte, error) {
return fs.ReadFile(f.target(p), p)
}
3 changes: 1 addition & 2 deletions coderd/files/overlay_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,11 +21,10 @@ func TestOverlayFS(t *testing.T) {
afero.WriteFile(b, ".terraform/modules/modules.json", []byte("{}"), 0o644)
afero.WriteFile(b, ".terraform/modules/example_module/main.tf", []byte("terraform {}"), 0o644)

it, err := files.NewOverlayFS(afero.NewIOFS(a), []files.Overlay{{
it := files.NewOverlayFS(afero.NewIOFS(a), []files.Overlay{{
Path: ".terraform/modules",
FS: afero.NewIOFS(b),
}})
require.NoError(t, err)

content, err := fs.ReadFile(it, "main.tf")
require.NoError(t, err)
Expand Down
9 changes: 1 addition & 8 deletions coderd/parameters.go
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Expand Up @@ -97,14 +97,7 @@ func (api *API) templateVersionDynamicParameters(rw http.ResponseWriter, r *http
return
}
defer api.FileCache.Release(tf.CachedModuleFiles.UUID)
templateFS, err = files.NewOverlayFS(templateFS, []files.Overlay{{Path: ".terraform/modules", FS: moduleFilesFS}})
if err != nil {
httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
Message: "Internal error creating overlay filesystem.",
Detail: err.Error(),
})
return
}
templateFS = files.NewOverlayFS(templateFS, []files.Overlay{{Path: ".terraform/modules", FS: moduleFilesFS}})
}
} else if !xerrors.Is(err, sql.ErrNoRows) {
httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
Expand Down
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