Allow setting a relative path in a relative URI (#1793)

Fixes: #1794
Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

src/core/uri/uri.cc

@@ -321,8 +321,8 @@ auto URI::path(const std::string &path) -> URI & {
   }
 
   const auto is_relative_path = path.starts_with(".");
-  if (is_relative_path) {
-    throw URIError{"You cannot set a relative path"};
+  if (is_relative_path && this->is_absolute()) {
+    throw URIError{"You cannot set a relative path to an absolute URI"};
   }
 
   if (path == "/") {
@@ -341,8 +341,8 @@ auto URI::path(std::string &&path) -> URI & {
   }
 
   const auto is_relative_path = path.starts_with(".");
-  if (is_relative_path) {
-    throw URIError{"You cannot set a relative path"};
+  if (is_relative_path && this->is_absolute()) {
+    throw URIError{"You cannot set a relative path to an absolute URI"};
   }
 
   if (path == "/") {

test/uri/uri_path_test.cc

@@ -285,6 +285,16 @@ TEST(URI_path_setter_no_scheme, set_path_with_port) {
   EXPECT_EQ(path, "");
 }
 
+TEST(URI_path_setter, lowercase_relative_path) {
+  sourcemeta::core::URI uri{"../SERVER.JSON"};
+  EXPECT_EQ(uri.recompose(), "../SERVER.JSON");
+  uri.path("../server.json");
+  EXPECT_EQ(uri.recompose(), "../server.json");
+  const auto const_path{"../foo.json"};
+  uri.path(const_path);
+  EXPECT_EQ(uri.recompose(), "../foo.json");
+}
+
 TEST(URI_path, append_path_without_path_from_root) {
   sourcemeta::core::URI uri{"http://example.com:8080"};
   uri.append_path("/test");