Mounted router fall back to parent router when route is not found

R/plumber-static.R

@@ -62,9 +62,10 @@ PlumberStatic <- R6Class(
         path <- httpuv::decodeURIComponent(path)
         abs.path <- resolve_path(direc, path)
         if (is.null(abs.path)) {
-          # TODO: Should this be inherited from a parent router?
-          val <- private$notFoundHandler(req=req, res=res)
-          return(val)
+          # If the file doesn't exist and isn't mounted,
+          # the 404 handler will be called anyways.
+          # So, we can always `forward()` here when the file isn't found.
+          return(forward())
         }
 
         ext <- tools::file_ext(abs.path)

R/plumber-step.R

@@ -20,6 +20,14 @@ resetForward <- function() {
   exec$forward <- FALSE
 }
 
+# Handle mounted routes not being found
+routeNotFound <- function() {
+  structure(list(), class = "plumber_route_not_found")
+}
+isRouteNotFound <- function(x) {
+  inherits(x, "plumber_route_not_found")
+}
+
 #' plumber step R6 class
 #' @description an object representing a step in the lifecycle of the treatment
 #' of a request by a plumber router.

R/plumber.R

@@ -767,13 +767,31 @@ Plumber <- R6Class(
         function(...) {
           resetForward()
           # TODO: support globbing?
-
           if (nchar(path) >= nchar(mountPath) && substr(path, 0, nchar(mountPath)) == mountPath) {
-            # This is a prefix match or exact match. Let this router handle.
+            # This is a prefix match or exact match. Let mount attempt handle.
+
+            # Mark that the route is being handled within a mount.
+            # Allows for the mount to forward to the next mount instead of 404.
+            prev_mount_status <- req$`_IS_MOUNT`
+            req$`_IS_MOUNT` <- TRUE
 
             # First trim the prefix off of the PATH_INFO element
+            cur_path_info <- req$PATH_INFO
             req$PATH_INFO <- substr(req$PATH_INFO, nchar(mountPath), nchar(req$PATH_INFO))
-            return(private$mnts[[mountPath]]$route(req, res))
+
+            # Handle route
+            ret <- private$mnts[[mountPath]]$route(req, res)
+
+            # Undo path info and mount status changes
+            req$PATH_INFO <- cur_path_info
+            req$`_IS_MOUNT` <- prev_mount_status
+
+            if (isRouteNotFound(ret)) {
+              # Forward to the parent router if mounted router can't handle route
+              return(forward())
+            }
+            # Return the regular value from the mounted router
+            return(ret)
           } else {
             return(forward())
           }
@@ -825,7 +843,15 @@ Plumber <- R6Class(
         }
 
         # Notify that there is no route found
-        private$notFoundHandler(req = req, res = res)
+        is_mount <- req$`_IS_MOUNT`
+        if (isTRUE(is_mount)) {
+          # If this is a mounted router, we need to forward to the parent router
+          # This value is used above when retrieving values from a mount
+          # Do not change this value without updating the recursive mount code above
+          return(routeNotFound())
+        } else {
+          private$notFoundHandler(req = req, res = res)
+        }
       }
       steps <- append(steps, list(notFoundStep))
 

tests/testthat/files/router.R

@@ -61,3 +61,17 @@ function(res){
 function(){
   "dual path"
 }
+
+#* @plumber
+function(pr) {
+  mnt_1 <-
+    pr() %>%
+    pr_get("/hello", function() "say hello")
+  mnt_2 <-
+    pr() %>%
+    pr_get("/world", function() "say hello world")
+
+  pr %>%
+    pr_mount("/say", mnt_1) %>%
+    pr_mount("/say/hello", mnt_2)
+}

tests/testthat/test-routing.R

@@ -20,6 +20,12 @@ test_that("Routing to errors and 404s works", {
   expect_equal(r$route(make_req("GET", "/path1"), res), "dual path")
   expect_equal(r$route(make_req("GET", "/path2"), res), "dual path")
 
+  ## Mounts fall back to parent router when route is not found
+  # Mount at `/say` with route `/hello`
+  expect_equal(r$route(make_req("GET", "/say/hello"), res), "say hello")
+  # Mount at `/say/hello` with route `/world`
+  expect_equal(r$route(make_req("GET", "/say/hello/world"), res), "say hello world")
+
   expect_equal(errors, 0)
   expect_equal(notFounds, 0)