actions: reuse preview path helpers in devtest mock

The mock had its own normalizeMockArtifactPath / chooseMockArtifactPath
that drifted from the production helpers (silent fallback to first file
on invalid input, instead of "" — the new no-fallback semantics). Export
GetRequestedPreviewPath and ChoosePreviewPath and call them from the mock
so behavior stays in sync.

Co-Authored-By: Claude (Opus 4.7) <noreply@anthropic.com>

routers/web/devtest/mock_actions.go

@@ -157,24 +157,12 @@ end_of_record
 	},
 }
 
-func normalizeMockArtifactPath(path string) string {
-	path = util.PathJoinRelX(path)
-	if path == "." {
-		return ""
+func mockArtifactFilePaths(files []mockArtifactFile) []string {
+	paths := make([]string, len(files))
+	for i, file := range files {
+		paths[i] = file.Path
 	}
-	return path
-}
-
-func chooseMockArtifactPath(files []mockArtifactFile, requestedPath string) string {
-	if len(files) == 0 {
-		return ""
-	}
-	for _, file := range files {
-		if file.Path == requestedPath {
-			return requestedPath
-		}
-	}
-	return files[0].Path
+	return paths
 }
 
 type generateMockStepsLogOptions struct {
@@ -534,11 +522,7 @@ func MockActionsArtifactPreview(ctx *context.Context) {
 		return
 	}
 
-	selectedPath := normalizeMockArtifactPath(strings.TrimPrefix(ctx.PathParam("*"), "/"))
-	if selectedPath == "" {
-		selectedPath = normalizeMockArtifactPath(ctx.Req.URL.Query().Get("path"))
-	}
-	selectedPath = chooseMockArtifactPath(files, selectedPath)
+	selectedPath := actions.ChoosePreviewPath(mockArtifactFilePaths(files), actions.GetRequestedPreviewPath(ctx))
 	previewFiles := make([]actions.ArtifactPreviewFile, 0, len(files))
 	for _, file := range files {
 		previewFiles = append(previewFiles, actions.ArtifactPreviewFile{
@@ -568,11 +552,7 @@ func MockActionsArtifactPreviewRaw(ctx *context.Context) {
 		return
 	}
 
-	selectedPath := normalizeMockArtifactPath(strings.TrimPrefix(ctx.PathParam("*"), "/"))
-	if selectedPath == "" {
-		selectedPath = normalizeMockArtifactPath(ctx.Req.URL.Query().Get("path"))
-	}
-	selectedPath = chooseMockArtifactPath(files, selectedPath)
+	selectedPath := actions.ChoosePreviewPath(mockArtifactFilePaths(files), actions.GetRequestedPreviewPath(ctx))
 	if selectedPath == "" {
 		ctx.NotFound(nil)
 		return

routers/web/repo/actions/view.go

@@ -1017,7 +1017,10 @@ func normalizeArtifactPreviewPath(path string) string {
 	return path
 }
 
-func getRequestedPreviewPath(ctx *context_module.Context) string {
+// GetRequestedPreviewPath reads the requested artifact preview path from a
+// request, accepting either the trailing `/preview/raw/*` path segment or a
+// `?path=` query parameter, and normalizes it to a safe relative path.
+func GetRequestedPreviewPath(ctx *context_module.Context) string {
 	path := strings.TrimPrefix(ctx.PathParam("*"), "/")
 	if path == "" {
 		path = ctx.Req.URL.Query().Get("path")
@@ -1033,10 +1036,10 @@ func artifactPreviewFallbackPath(artifact *actions_model.ActionArtifact) string
 	return artifact.ArtifactName
 }
 
-// choosePreviewPath resolves the preview path to render.
+// ChoosePreviewPath resolves the preview path to render.
 // An empty `requested` means no path was specified, so the first file is selected as a default.
 // A non-empty `requested` that is not present in `paths` returns "" so callers can 404 instead of silently swapping to a different file.
-func choosePreviewPath(paths []string, requested string) string {
+func ChoosePreviewPath(paths []string, requested string) string {
 	if len(paths) == 0 {
 		return ""
 	}
@@ -1249,7 +1252,7 @@ func ArtifactsPreviewView(ctx *context_module.Context) {
 		ctx.ServerError("listPreviewPaths", err)
 		return
 	}
-	selectedPath := choosePreviewPath(paths, getRequestedPreviewPath(ctx))
+	selectedPath := ChoosePreviewPath(paths, GetRequestedPreviewPath(ctx))
 
 	previewFiles := make([]ArtifactPreviewFile, 0, len(paths))
 	for _, path := range paths {
@@ -1289,7 +1292,7 @@ func ArtifactsPreviewRawView(ctx *context_module.Context) {
 		ctx.ServerError("listPreviewPaths", err)
 		return
 	}
-	selectedPath := choosePreviewPath(paths, getRequestedPreviewPath(ctx))
+	selectedPath := ChoosePreviewPath(paths, GetRequestedPreviewPath(ctx))
 	if selectedPath == "" {
 		ctx.HTTPError(http.StatusNotFound, "artifact file not found")
 		return