Fix #1123

Author: Scripter17

url/src/lib.rs

@@ -1759,6 +1759,13 @@ impl Url {
     /// assert_eq!(url.as_str(), "https://example.com/api/some%20comments");
     /// assert_eq!(url.path(), "/api/some%20comments");
     ///
+    /// // `set_path` will encode leading `/` and trailing ` ` in cannot-be-a-base paths.
+    /// let mut url = Url::parse("a:  ?")?;
+    /// assert_eq!(url.path(), " %20");
+    /// url.set_query(None);
+    /// url.set_path("/  ");
+    /// assert_eq!(url.path(), "%2F %20");
+    ///
     /// # Ok(())
     /// # }
     /// # run().unwrap();

url/src/parser.rs

@@ -1431,6 +1431,10 @@ impl Parser<'_> {
                 Some(('?', _)) | Some(('#', _)) if self.context == Context::UrlParser => {
                     return input_before_c
                 }
+                Some((' ', _)) if input.starts_with('?') || input.starts_with('#') || input.is_empty() => {
+                    self.serialization.push_str("%20");
+                    return input;
+                }
                 Some((c, utf8_c)) => {
                     self.check_url_code_point(c, &input);
                     self.serialization