Fix inconsistent query_to_string with +

Author: ghivert

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## v0.66.0 - 2025-10-21
 
 - The `tap` function from the `function` module has been deprecated.
+- `uri.query_to_string` now correctly handles `+` in query params.
 
 ## v0.65.0 - 2025-09-29
 

src/gleam/uri.gleam

@@ -556,7 +556,13 @@ pub fn query_to_string(query: List(#(String, String))) -> String {
 }
 
 fn query_pair(pair: #(String, String)) -> StringTree {
-  string_tree.from_strings([percent_encode(pair.0), "=", percent_encode(pair.1)])
+  [percent_encode_query(pair.0), "=", percent_encode_query(pair.1)]
+  |> string_tree.from_strings
+}
+
+fn percent_encode_query(part: String) -> String {
+  percent_encode(part)
+  |> string.replace(each: "+", with: "%2B")
 }
 
 /// Encodes a string into a percent encoded representation.

test/gleam/uri_test.gleam

@@ -413,6 +413,12 @@ pub fn query_to_string_test() {
   assert query_string == "weebl%20bob=1&city=%C3%B6rebro"
 }
 
+pub fn query_to_string_special_characters_test() {
+  let query_string =
+    uri.query_to_string([#("weebl bob", "1+1-1*1.1~1!1'1(1);%")])
+  assert query_string == "weebl%20bob=1%2B1-1*1.1~1!1'1(1)%3B%25"
+}
+
 pub fn empty_query_to_string_test() {
   let query_string = uri.query_to_string([])
   assert query_string == ""
@@ -557,6 +563,13 @@ pub fn parse_segments_test() {
   assert uri.path_segments("/weebl/../bob") == ["bob"]
 }
 
+pub fn query_to_string_parse_query_opposite_unreserved_marks_test() {
+  let queries = [#("weebl bob", "1+1-1*1.1~1!1'1(1);%"), #("city", "örebro")]
+  let query_string = uri.query_to_string(queries)
+  let parsed = uri.parse_query(query_string)
+  assert parsed == Ok(queries)
+}
+
 pub fn origin1_test() {
   let assert Ok(parsed) = uri.parse("http://example.test/path?weebl#bob")
   assert uri.origin(parsed) == Ok("http://example.test")