Fix URI::resolve_from when dealing with file bases (#1797)

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

Author: jviotti

src/core/uri/uri.cc

@@ -556,17 +556,24 @@ auto URI::canonicalize() -> URI & {
 }
 
 auto URI::resolve_from(const URI &base) -> URI & {
+  const bool is_file{base.scheme_ == "file"};
+  auto copy = base;
+  if (is_file) {
+    // Huge hack, but otherwise `uriparser` will resolve in a weird way
+    copy.host_ = "placeholder";
+  }
+
   UriUriA absoluteDest;
   // Looks like this function allocates to the output variable
   // even on failure.
   // See https://uriparser.github.io/doc/api/latest/
   switch (uriAddBaseUriExA(&absoluteDest, &this->internal->uri,
-                           &base.internal->uri, URI_RESOLVE_STRICTLY)) {
+                           &copy.internal->uri, URI_RESOLVE_STRICTLY)) {
     case URI_SUCCESS:
       break;
     case URI_ERROR_ADDBASE_REL_BASE:
       uriFreeUriMembersA(&absoluteDest);
-      assert(!base.is_absolute());
+      assert(!copy.is_absolute());
       throw URIError{"Base URI is not absolute"};
     default:
       uriFreeUriMembersA(&absoluteDest);

test/uri/uri_resolve_from_test.cc

@@ -108,3 +108,18 @@ TEST(URI_resolve_from, rfc3986_resolve_with_absolute_path) {
   absolute_path.resolve_from(base);
   EXPECT_EQ(absolute_path.recompose(), "s://h/x");
 }
+
+TEST(URI_resolve_from, file_1) {
+  const sourcemeta::core::URI base{"file:///foo/bar/baz"};
+  sourcemeta::core::URI relative{"./qux"};
+  relative.resolve_from(base);
+  EXPECT_EQ(relative.recompose(), "file:///foo/bar/qux");
+}
+
+TEST(URI_resolve_from, file_from_path) {
+  const std::filesystem::path base_path{"/foo/bar/baz"};
+  const auto base{sourcemeta::core::URI::from_path(base_path)};
+  sourcemeta::core::URI relative{"./qux"};
+  relative.resolve_from(base);
+  EXPECT_EQ(relative.recompose(), "file:///foo/bar/qux");
+}