Allow colon to be escaped when building the path segments (#1287)

Author: zraul123

lib/plug/router.ex

@@ -74,6 +74,14 @@ defmodule Plug.Router do
   The above will match `/hello/foo.json` but not `/hello/foo`.
   Other delimiters such as `-`, `@` may be used to denote suffixes.
 
+  Identifier matching can be escaped using the `\` character:
+
+      get "/hello/\\:greet" do
+        send_resp(conn, 200, "hello")
+      end
+
+  The above will only match `/hello/:greet`.
+
   Routes allow for globbing which will match the remaining parts
   of a route. A glob match is done with the `*` character followed
   by the variable name. Typically you prefix the variable name with
@@ -90,6 +98,15 @@ defmodule Plug.Router do
         send_resp(conn, 200, "route after /hello: #{inspect glob}")
       end
 
+  Similarly to `:identifiers`, globs are also escaped using the
+  `\` character:
+
+      get "/hello/\\*glob" do
+        send_resp(conn, 200, "this is not a glob route")
+      end
+
+  The above will only match `/hello/*glob`.
+
   Opposite to `:identifiers`, globs do not allow prefix nor suffix
   matches.
 

lib/plug/router/utils.ex

@@ -127,7 +127,7 @@ defmodule Plug.Router.Utils do
   including the known parameters.
   """
   def build_path_clause(path, guard, context \\ nil) when is_binary(path) do
-    compiled = :binary.compile_pattern([":", "*"])
+    compiled = :binary.compile_pattern(["\\:", "\\*", ":", "*"])
 
     {params, match, guards, post_match} =
       path
@@ -148,6 +148,15 @@ defmodule Plug.Router.Utils do
       [] ->
         build_path_clause(rest, params, [segment | match], guards, post_match, context, compiled)
 
+      [{prefix_size, match_length}] when match_length == 2 ->
+        suffix_size = byte_size(segment) - prefix_size - 2
+
+        <<prefix::binary-size(prefix_size), ?\\, char, suffix::binary-size(suffix_size)>> =
+          segment
+
+        escaped_segment = [prefix <> <<char>> <> suffix | match]
+        build_path_clause(rest, params, escaped_segment, guards, post_match, context, compiled)
+
       [{prefix_size, _}] ->
         suffix_size = byte_size(segment) - prefix_size - 1
         <<prefix::binary-size(prefix_size), char, suffix::binary-size(suffix_size)>> = segment

test/plug/router/utils_test.exs

@@ -60,6 +60,20 @@ defmodule Plug.Router.UtilsTest do
              build_path_match("foo/bar:username")
   end
 
+  test "build match with escaped identifiers" do
+    assert quote(@opts, do: {[], ["foo", ":"]}) == build_path_match("foo/\\:")
+    assert quote(@opts, do: {[], ["foo", ":id"]}) == build_path_match("/foo/\\:id")
+    assert quote(@opts, do: {[], ["foo", ":username"]}) == build_path_match("foo/\\:username")
+
+    assert quote(@opts, do: {[:id, :post_id], ["foo", id, ":name", post_id]}) ==
+             build_path_match("/foo/:id/\\:name/:post_id")
+
+    assert quote(@opts, do: {[], ["foo", "bar-:id"]}) == build_path_match("/foo/bar-\\:id")
+
+    assert quote(@opts, do: {[], ["foo", "bar:batchDelete"]}) ==
+             build_path_match("foo/bar\\:batchDelete")
+  end
+
   test "build match only with glob" do
     assert quote(@opts, do: {[:bar], bar}) == build_path_match("*bar")
     assert quote(@opts, do: {[:glob], glob}) == build_path_match("/*glob")
@@ -70,6 +84,14 @@ defmodule Plug.Router.UtilsTest do
     assert quote(@opts, do: {[:glob], ["foo" | glob]}) == build_path_match("foo/*glob")
   end
 
+  test "build match with escaped glob" do
+    assert quote(@opts, do: {[], ["*bar"]}) == build_path_match("\\*bar")
+    assert quote(@opts, do: {[], ["*glob"]}) == build_path_match("/\\*glob")
+
+    assert quote(@opts, do: {[], ["foo", "*bar"]}) == build_path_match("/foo/\\*bar")
+    assert quote(@opts, do: {[], ["foo", "*glob"]}) == build_path_match("foo/\\*glob")
+  end
+
   test "build invalid match with empty matches" do
     assert_raise Plug.Router.InvalidSpecError,
                  "invalid dynamic path. The characters : and * must be immediately followed by lowercase letters or underscore, got: :",