Fix handling of NULL values in sqlpage.link

NULL values were encoded as the string `'null'` instead of being omitted
from the link's parameters.

Author: lovasoa

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## O.37.1
  - fixed decoding of UUID values
+ - Fixed handling of NULL values in `sqlpage.link`. They were encoded as the string `'null'` instead of being omitted from the link's parameters.
 
 ## v0.37.0
  - We now cryptographically sign the Windows app during releases, which proves the file hasn’t been tampered with. Once the production certificate is active, Windows will show a "verified publisher" and should stop showing screens saying "This app might harm your device", "Windows protected your PC" or "Are you sure you want to run this application ?". 

src/webserver/database/sqlpage_functions/functions.rs

@@ -372,11 +372,14 @@ async fn link<'a>(
 ) -> anyhow::Result<String> {
     let mut url = file.into_owned();
     if let Some(parameters) = parameters {
-        url.push('?');
         let encoded = serde_json::from_str::<URLParameters>(&parameters).with_context(|| {
             format!("link: invalid URL parameters: not a valid json object:\n{parameters}")
         })?;
-        url.push_str(encoded.get());
+        let encoded_str = encoded.get();
+        if !encoded_str.is_empty() {
+            url.push('?');
+            url.push_str(encoded_str);
+        }
     }
     if let Some(hash) = hash {
         url.push('#');

src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs

@@ -48,8 +48,10 @@ impl<'de> Deserialize<'de> for URLParameters {
                     map.next_entry::<Cow<str>, Cow<serde_json::value::RawValue>>()?
                 {
                     let value = value.get();
-                    if let Ok(str_val) = serde_json::from_str::<Cow<str>>(value) {
-                        out.push_kv(&key, &str_val);
+                    if let Ok(str_val) = serde_json::from_str::<Option<Cow<str>>>(value) {
+                        if let Some(str_val) = str_val {
+                            out.push_kv(&key, &str_val);
+                        }
                     } else if let Ok(vec_val) =
                         serde_json::from_str::<Vec<serde_json::Value>>(value)
                     {
@@ -96,6 +98,18 @@ fn test_url_parameters_deserializer() {
     );
 }
 
+#[test]
+fn test_url_parameters_null() {
+    use serde_json::json;
+    let json = json!({
+        "null_should_be_omitted": null,
+        "x": "hello",
+    });
+
+    let url_parameters: URLParameters = serde_json::from_value(json).unwrap();
+    assert_eq!(url_parameters.0, "x=hello");
+}
+
 #[test]
 fn test_url_parameters_deserializer_special_chars() {
     use serde_json::json;

tests/sql_test_files/it_works_link_null.sql

@@ -0,0 +1,5 @@
+select 'text' as component, 
+    case sqlpage.link('test.sql', json_object('x', null))
+        when 'test.sql' then 'It works !'
+        else 'error: ' || coalesce(sqlpage.link('test.sql', json_object('x', null)), 'NULL')
+    end AS contents;