Ensures that mount()'d routes have a leading slash.

This also adds some small tests for correct handling of both leading and
trailing slashes in mount paths.

Co-authored-by: Winston Chang <winston@stdout.org>

NEWS.md

@@ -54,6 +54,8 @@ plumber 0.5.0
 
 ### Bug fixes
 
+* Fix possible bugs due to mounted routers without leading slashes (@atheriel, [#476](https://github.com/trestletech/plumber/issues/476) [#501](https://github.com/trestletech/plumber/pull/501)).
+
 * Fix bug preventing error handling when a serializer fails (@antoine-sachet, [#490](https://github.com/rstudio/plumber/pull/490))
 
 * Fix URL-decoding of query parameters and URL-encoding/decoding of cookies. Both now use `httpuv::decodeURIComponent` instead of `httpuv::decodeURI`. (@antoine-sachet, [#462](https://github.com/trestletech/plumber/pull/462))

R/plumber.R

@@ -322,7 +322,13 @@ plumber <- R6Class(
       httpuv::runServer(host, port, self)
     },
     mount = function(path, router){
-      path <- sub("([^/])$", "\\1/", path)
+      # Ensure that the path has both a leading and trailing slash.
+      if (!startsWith(path, "/")) {
+        path <- paste0("/", path)
+      }
+      if (!endsWith(path, "/")) {
+        path <- paste0(path, "/")
+      }
 
       private$mnts[[path]] <- router
     },

tests/testthat/test-plumber.R

@@ -150,9 +150,17 @@ test_that("mounts can be read correctly", {
 
   stat <- PlumberStatic$new(".")
   pr$mount("/static", stat)
+  pr$mount("missing-slashes", stat)
+  pr$mount("/both-slashes/", stat)
+  pr$mount("trailing-slash/", stat)
+  pr$mount("/extra-slash//", stat)
 
-  expect_length(pr$routes, 3)
+  expect_length(pr$routes, 7)
   expect_s3_class(pr$mounts[["/static/"]], "plumberstatic")
+  expect_s3_class(pr$mounts[["/missing-slashes/"]], "plumberstatic")
+  expect_s3_class(pr$mounts[["/both-slashes/"]], "plumberstatic")
+  expect_s3_class(pr$mounts[["/trailing-slash/"]], "plumberstatic")
+  expect_s3_class(pr$mounts[["/extra-slash//"]], "plumberstatic")
   expect_s3_class(pr$mounts[["/mysubpath/"]], "plumber")
 })