feat: load terraform modules when using dynamic parameters (#17714)

coderd/files/overlay.go

@@ -0,0 +1,86 @@
+package files
+
+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.
+type overlayFS struct {
+	baseFS   fs.FS
+	overlays []Overlay
+}
+
+type Overlay struct {
+	Path string
+	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)
+		}
+	}
+
+	return overlayFS{
+		baseFS:   baseFS,
+		overlays: overlays,
+	}, nil
+}
+
+func (f overlayFS) Open(p string) (fs.File, error) {
+	for _, overlay := range f.overlays {
+		if strings.HasPrefix(path.Clean(p), overlay.Path) {
+			return overlay.FS.Open(p)
+		}
+	}
+	return f.baseFS.Open(p)
+}
+
+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) 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)
+}
+
+// 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
+}

coderd/files/overlay_test.go

@@ -0,0 +1,44 @@
+package files_test
+
+import (
+	"io/fs"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/v2/coderd/files"
+)
+
+func TestOverlayFS(t *testing.T) {
+	t.Parallel()
+
+	a := afero.NewMemMapFs()
+	afero.WriteFile(a, "main.tf", []byte("terraform {}"), 0o644)
+	afero.WriteFile(a, ".terraform/modules/example_module/main.tf", []byte("inaccessible"), 0o644)
+	afero.WriteFile(a, ".terraform/modules/other_module/main.tf", []byte("inaccessible"), 0o644)
+	b := afero.NewMemMapFs()
+	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{{
+		Path: ".terraform/modules",
+		FS:   afero.NewIOFS(b),
+	}})
+	require.NoError(t, err)
+
+	content, err := fs.ReadFile(it, "main.tf")
+	require.NoError(t, err)
+	require.Equal(t, "terraform {}", string(content))
+
+	_, err = fs.ReadFile(it, ".terraform/modules/other_module/main.tf")
+	require.Error(t, err)
+
+	content, err = fs.ReadFile(it, ".terraform/modules/modules.json")
+	require.NoError(t, err)
+	require.Equal(t, "{}", string(content))
+
+	content, err = fs.ReadFile(it, ".terraform/modules/example_module/main.tf")
+	require.NoError(t, err)
+	require.Equal(t, "terraform {}", string(content))
+}