overlay terraform modules on template files fs

aslilac · aslilac · commit d6ea3037a7ce · 2025-05-07T22:43:20.000Z
diff --git a/coderd/files/overlay.go b/coderd/files/overlay.go
@@ -0,0 +1,42 @@
+package files
+
+import (
+	"io/fs"
+	"path"
+	"strings"
+)
+
+type overlay struct {
+	baseFS      fs.FS
+	overlayFS   fs.FS
+	overlayPath string
+}
+
+func NewOverlayFS(baseFS, overlayFS fs.FS, overlayPath string) fs.FS {
+	return overlay{
+		baseFS:      baseFS,
+		overlayFS:   overlayFS,
+		overlayPath: path.Clean(overlayPath),
+	}
+}
+
+func (f overlay) Open(p string) (fs.File, error) {
+	if strings.HasPrefix(path.Clean(p), f.overlayPath) {
+		return f.overlayFS.Open(p)
+	}
+	return f.baseFS.Open(p)
+}
+
+func (f overlay) ReadDir(p string) ([]fs.DirEntry, error) {
+	if strings.HasPrefix(path.Clean(p), f.overlayPath) {
+		return f.overlayFS.(fs.ReadDirFS).ReadDir(p)
+	}
+	return f.baseFS.(fs.ReadDirFS).ReadDir(p)
+}
+
+func (f overlay) ReadFile(p string) ([]byte, error) {
+	if strings.HasPrefix(path.Clean(p), f.overlayPath) {
+		return f.overlayFS.(fs.ReadFileFS).ReadFile(p)
+	}
+	return f.baseFS.(fs.ReadFileFS).ReadFile(p)
+}
diff --git a/coderd/parameters.go b/coderd/parameters.go
@@ -13,6 +13,7 @@ import (
 
 	"github.com/coder/coder/v2/coderd/database"
 	"github.com/coder/coder/v2/coderd/database/dbauthz"
+	"github.com/coder/coder/v2/coderd/files"
 	"github.com/coder/coder/v2/coderd/httpapi"
 	"github.com/coder/coder/v2/coderd/httpmw"
 	"github.com/coder/coder/v2/codersdk"
@@ -68,7 +69,7 @@ func (api *API) templateVersionDynamicParameters(rw http.ResponseWriter, r *http
 		return
 	}
 
-	fs, err := api.FileCache.Acquire(fileCtx, fileID)
+	templateFS, err := api.FileCache.Acquire(fileCtx, fileID)
 	defer api.FileCache.Release(fileID)
 	if err != nil {
 		httpapi.Write(ctx, rw, http.StatusNotFound, codersdk.Response{
@@ -85,6 +86,19 @@ func (api *API) templateVersionDynamicParameters(rw http.ResponseWriter, r *http
 	tf, err := api.Database.GetTemplateVersionTerraformValues(ctx, templateVersion.ID)
 	if err == nil {
 		plan = tf.CachedPlan
+
+		if tf.CachedModuleFiles.Valid {
+			moduleFilesFS, err := api.FileCache.Acquire(fileCtx, tf.CachedModuleFiles.UUID)
+			defer api.FileCache.Release(tf.CachedModuleFiles.UUID)
+			if err != nil {
+				httpapi.Write(ctx, rw, http.StatusNotFound, codersdk.Response{
+					Message: "Internal error fetching Terraform modules.",
+					Detail:  err.Error(),
+				})
+				return
+			}
+			templateFS = files.NewOverlayFS(templateFS, moduleFilesFS, ".terraform/modules")
+		}
 	} else if !xerrors.Is(err, sql.ErrNoRows) {
 		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
 			Message: "Failed to retrieve Terraform values for template version",
@@ -124,7 +138,7 @@ func (api *API) templateVersionDynamicParameters(rw http.ResponseWriter, r *http
 	)
 
 	// Send an initial form state, computed without any user input.
-	result, diagnostics := preview.Preview(ctx, input, fs)
+	result, diagnostics := preview.Preview(ctx, input, templateFS)
 	response := codersdk.DynamicParametersResponse{
 		ID:          -1,
 		Diagnostics: previewtypes.Diagnostics(diagnostics),
@@ -152,7 +166,7 @@ func (api *API) templateVersionDynamicParameters(rw http.ResponseWriter, r *http
 				return
 			}
 			input.ParameterValues = update.Inputs
-			result, diagnostics := preview.Preview(ctx, input, fs)
+			result, diagnostics := preview.Preview(ctx, input, templateFS)
 			response := codersdk.DynamicParametersResponse{
 				ID:          update.ID,
 				Diagnostics: previewtypes.Diagnostics(diagnostics),
