From 0e89124079f54a114d5143f56234dbc0b39406d6 Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Sat, 22 Nov 2025 23:46:22 +0000
Subject: [PATCH 01/12] feat: Add sqlpage.set_variable function

Co-authored-by: contact <contact@ophir.dev>
---
 CHANGELOG.md                                  |  3 +
 examples/official-site/component.sql          |  2 +-
 examples/official-site/examples/layouts.sql   |  4 +-
 examples/official-site/functions.sql          |  4 +-
 .../sqlpage/migrations/70_set_variable.sql    | 60 +++++++++++++++++++
 .../database/sqlpage_functions/functions.rs   | 34 +++++++++++
 .../sql_test_files/it_works_set_variable.sql  |  9 ++-
 .../it_works_set_variable_null.sql            |  7 +++
 .../it_works_set_variable_replace.sql         |  7 +++
 9 files changed, 123 insertions(+), 7 deletions(-)
 create mode 100644 examples/official-site/sqlpage/migrations/70_set_variable.sql
 create mode 100644 tests/sql_test_files/it_works_set_variable_null.sql
 create mode 100644 tests/sql_test_files/it_works_set_variable_replace.sql

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 026d4b94..85fcb39d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,9 @@
 # CHANGELOG.md
 
 ## unrelease
+ - **New Function**: `sqlpage.set_variable(name, value)`
+   - Returns a URL with the specified variable set to the given value, preserving other existing variables.
+   - This is a shorthand for `sqlpage.link(sqlpage.path(), json_patch(sqlpage.variables('get'), json_object(name, value)))`.
  - **Variable System Improvements**: URL and POST parameters are now immutable, preventing accidental modification. User-defined variables created with `SET` remain mutable.
    - **BREAKING**: `$variable` no longer accesses POST parameters. Use `:variable` instead.
      - **What changed**: Previously, `$x` would return a POST parameter value if no GET parameter named `x` existed.
diff --git a/examples/official-site/component.sql b/examples/official-site/component.sql
index 05d4c30c..c10943f3 100644
--- a/examples/official-site/component.sql
+++ b/examples/official-site/component.sql
@@ -149,6 +149,6 @@ select
 select
     name as title,
     icon,
-    sqlpage.link('component.sql', json_object('component', name)) as link
+    sqlpage.set_variable('component', name) as link
 from component
 order by name;
\ No newline at end of file
diff --git a/examples/official-site/examples/layouts.sql b/examples/official-site/examples/layouts.sql
index 13e81750..1169d771 100644
--- a/examples/official-site/examples/layouts.sql
+++ b/examples/official-site/examples/layouts.sql
@@ -30,7 +30,7 @@ For more information on how to use layouts, see the [shell component documentati
 select 'list' as component, 'Available SQLPage shell layouts' as title;
 select 
     column1 as title,
-    sqlpage.link('', json_object('layout', lower(column1), 'sidebar', $sidebar)) as link,
+    sqlpage.set_variable('layout', lower(column1)) as link,
     $layout = lower(column1) as active,
     column3 as icon,
     column2 as description
@@ -43,7 +43,7 @@ from (VALUES
 select 'list' as component, 'Available Menu layouts' as title;
 select
     column1 as title,
-    sqlpage.link('', json_object('layout', $layout, 'sidebar', column1 = 'Sidebar')) as link,
+    sqlpage.set_variable('sidebar', column1 = 'Sidebar') as link,
     (column1 = 'Sidebar' AND $sidebar = 1) OR (column1 = 'Horizontal' AND $sidebar = 0) as active,
     column2 as description,
     column3 as icon
diff --git a/examples/official-site/functions.sql b/examples/official-site/functions.sql
index 943bfe16..5b8f4a8d 100644
--- a/examples/official-site/functions.sql
+++ b/examples/official-site/functions.sql
@@ -11,7 +11,7 @@ FROM example WHERE component = 'shell' LIMIT 1;
 select 'breadcrumb' as component;
 select 'SQLPage' as title, '/' as link, 'Home page' as description;
 select 'Functions' as title, '/functions.sql' as link, 'List of all functions' as description;
-select $function as title, sqlpage.link('functions.sql', json_object('function', $function)) as link where $function IS NOT NULL;
+select $function as title, sqlpage.set_variable('function', $function) as link where $function IS NOT NULL;
 
 select 'text' as component, 'SQLPage built-in functions' as title where $function IS NULL;
 select '
@@ -60,7 +60,7 @@ select
 select
     name as title,
     icon,
-    sqlpage.link('functions.sql', json_object('function', name)) as link
+    sqlpage.set_variable('function', name) as link
 from sqlpage_functions
 where $function IS NOT NULL
 order by name;
\ No newline at end of file
diff --git a/examples/official-site/sqlpage/migrations/70_set_variable.sql b/examples/official-site/sqlpage/migrations/70_set_variable.sql
new file mode 100644
index 00000000..1a213656
--- /dev/null
+++ b/examples/official-site/sqlpage/migrations/70_set_variable.sql
@@ -0,0 +1,60 @@
+INSERT INTO
+    sqlpage_functions (
+        "name",
+        "introduced_in_version",
+        "icon",
+        "description_md"
+    )
+VALUES
+    (
+        'set_variable',
+        '0.40.0',
+        'variable',
+        'Returns a URL that is the same as the current page''s URL, but with a variable set to a new value.
+        
+This function is useful when you want to create a link that changes a parameter on the current page, while preserving other parameters.
+
+It is equivalent to `sqlpage.link(sqlpage.path(), json_patch(sqlpage.variables(''get''), json_object(name, value)))`.
+
+### Example
+
+Let''s say you have a list of products, and you want to filter them by category. You can use `sqlpage.set_variable` to create links that change the category filter, without losing other potential filters (like a search query or a sort order).
+
+```sql
+select ''button'' as component, ''sm'' as size, ''center'' as justify;
+select 
+    category as title,
+    sqlpage.set_variable(''category'', category) as link,
+    case when $category = category then ''primary'' else ''secondary'' end as color
+from categories;
+```
+
+### Parameters
+ - `name` (TEXT): The name of the variable to set.
+ - `value` (TEXT): The value to set the variable to. If `NULL` is passed, the variable is removed from the URL.
+'
+    );
+
+INSERT INTO
+    sqlpage_function_parameters (
+        "function",
+        "index",
+        "name",
+        "description_md",
+        "type"
+    )
+VALUES
+    (
+        'set_variable',
+        1,
+        'name',
+        'The name of the variable to set.',
+        'TEXT'
+    ),
+    (
+        'set_variable',
+        2,
+        'value',
+        'The value to set the variable to.',
+        'TEXT'
+    );
diff --git a/src/webserver/database/sqlpage_functions/functions.rs b/src/webserver/database/sqlpage_functions/functions.rs
index ece488b8..47225d37 100644
--- a/src/webserver/database/sqlpage_functions/functions.rs
+++ b/src/webserver/database/sqlpage_functions/functions.rs
@@ -46,6 +46,7 @@ super::function_definition_macro::sqlpage_functions! {
     read_file_as_text((&RequestInfo), file_path: Option<Cow<str>>);
     request_method((&RequestInfo));
     run_sql((&ExecutionContext, &mut DbConn), sql_file_path: Option<Cow<str>>, variables: Option<Cow<str>>);
+    set_variable((&ExecutionContext), name: Cow<str>, value: Option<Cow<str>>);
 
     uploaded_file_mime_type((&RequestInfo), upload_name: Cow<str>);
     uploaded_file_path((&RequestInfo), upload_name: Cow<str>);
@@ -612,6 +613,39 @@ async fn run_sql<'a>(
     Ok(Some(Cow::Owned(String::from_utf8(json_results_bytes)?)))
 }
 
+async fn set_variable<'a>(
+    context: &'a ExecutionContext,
+    name: Cow<'a, str>,
+    value: Option<Cow<'a, str>>,
+) -> anyhow::Result<String> {
+    let mut params_map = serde_json::Map::with_capacity(context.url_params.len() + 1);
+
+    for (k, v) in &context.url_params {
+        params_map.insert(k.clone(), serde_json::to_value(v)?);
+    }
+
+    if let Some(value) = value {
+        params_map.insert(
+            name.into_owned(),
+            serde_json::Value::String(value.into_owned()),
+        );
+    } else {
+        params_map.remove(&*name);
+    }
+
+    let json_val = serde_json::Value::Object(params_map);
+    let encoded: URLParameters = serde_json::from_value(json_val)?;
+
+    let mut url = context.path.clone();
+    let encoded_str = encoded.get();
+    if !encoded_str.is_empty() {
+        url.push('?');
+        url.push_str(encoded_str);
+    }
+
+    Ok(url)
+}
+
 #[tokio::test]
 async fn test_hash_password() {
     let s = hash_password(Some("password".to_string()))
diff --git a/tests/sql_test_files/it_works_set_variable.sql b/tests/sql_test_files/it_works_set_variable.sql
index e9ac8286..3f79718d 100644
--- a/tests/sql_test_files/it_works_set_variable.sql
+++ b/tests/sql_test_files/it_works_set_variable.sql
@@ -1,2 +1,7 @@
-set what_does_it_do = 'wo' || 'rks';
-select 'text' as component, 'It ' || $what_does_it_do || ' !' as contents;
+set url = sqlpage.set_variable('y', '2');
+set path = sqlpage.path();
+select 'text' as component,
+    case
+        when $url = $path || '?x=1&y=2' OR $url = $path || '?y=2&x=1' THEN 'It works !'
+        else 'error: ' || $url
+    end as contents;
diff --git a/tests/sql_test_files/it_works_set_variable_null.sql b/tests/sql_test_files/it_works_set_variable_null.sql
new file mode 100644
index 00000000..471ea6c6
--- /dev/null
+++ b/tests/sql_test_files/it_works_set_variable_null.sql
@@ -0,0 +1,7 @@
+set url = sqlpage.set_variable('x', null);
+set path = sqlpage.path();
+select 'text' as component,
+    case
+        when $url = $path THEN 'It works !'
+        else 'error: ' || $url
+    end as contents;
diff --git a/tests/sql_test_files/it_works_set_variable_replace.sql b/tests/sql_test_files/it_works_set_variable_replace.sql
new file mode 100644
index 00000000..9ad99b85
--- /dev/null
+++ b/tests/sql_test_files/it_works_set_variable_replace.sql
@@ -0,0 +1,7 @@
+set url = sqlpage.set_variable('x', '2');
+set path = sqlpage.path();
+select 'text' as component,
+    case
+        when $url = $path || '?x=2' THEN 'It works !'
+        else 'error: ' || $url
+    end as contents;

From d1e7cfdb8936564dd90609a3c961019077976e1b Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Sun, 23 Nov 2025 00:17:33 +0000
Subject: [PATCH 02/12] Refactor: Fix set_variable serialization and update
 tests

Co-authored-by: contact <contact@ophir.dev>
---
 .../migrations/{70_set_variable.sql => 71_set_variable.sql}  | 0
 src/webserver/database/sqlpage_functions/functions.rs        | 2 +-
 tests/sql_test_files/it_works_set_variable.sql               | 5 ++++-
 3 files changed, 5 insertions(+), 2 deletions(-)
 rename examples/official-site/sqlpage/migrations/{70_set_variable.sql => 71_set_variable.sql} (100%)

diff --git a/examples/official-site/sqlpage/migrations/70_set_variable.sql b/examples/official-site/sqlpage/migrations/71_set_variable.sql
similarity index 100%
rename from examples/official-site/sqlpage/migrations/70_set_variable.sql
rename to examples/official-site/sqlpage/migrations/71_set_variable.sql
diff --git a/src/webserver/database/sqlpage_functions/functions.rs b/src/webserver/database/sqlpage_functions/functions.rs
index 47225d37..0eaf4f76 100644
--- a/src/webserver/database/sqlpage_functions/functions.rs
+++ b/src/webserver/database/sqlpage_functions/functions.rs
@@ -634,7 +634,7 @@ async fn set_variable<'a>(
     }
 
     let json_val = serde_json::Value::Object(params_map);
-    let encoded: URLParameters = serde_json::from_value(json_val)?;
+    let encoded: URLParameters = serde_json::from_str(&json_val.to_string())?;
 
     let mut url = context.path.clone();
     let encoded_str = encoded.get();
diff --git a/tests/sql_test_files/it_works_set_variable.sql b/tests/sql_test_files/it_works_set_variable.sql
index 3f79718d..24793b1d 100644
--- a/tests/sql_test_files/it_works_set_variable.sql
+++ b/tests/sql_test_files/it_works_set_variable.sql
@@ -1,7 +1,10 @@
 set url = sqlpage.set_variable('y', '2');
 set path = sqlpage.path();
+set x = json_extract(sqlpage.variables('get'), '$.x');
+
 select 'text' as component,
     case
-        when $url = $path || '?x=1&y=2' OR $url = $path || '?y=2&x=1' THEN 'It works !'
+        when $x is not null AND ($url = $path || '?x=' || $x || '&y=2' OR $url = $path || '?y=2&x=' || $x) THEN 'It works !'
+        when $x is null AND $url = $path || '?y=2' THEN 'It works !'
         else 'error: ' || $url
     end as contents;

From c1f4c5503b8b545e8b2bef751864c722a86a371a Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 00:59:53 +0100
Subject: [PATCH 03/12] fix tests: no json_extract on mssql

---
 ...t_works_set_variable.sql => it_works_set_variable_nomssql.sql} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename tests/sql_test_files/{it_works_set_variable.sql => it_works_set_variable_nomssql.sql} (100%)

diff --git a/tests/sql_test_files/it_works_set_variable.sql b/tests/sql_test_files/it_works_set_variable_nomssql.sql
similarity index 100%
rename from tests/sql_test_files/it_works_set_variable.sql
rename to tests/sql_test_files/it_works_set_variable_nomssql.sql

From a3c33e456de975b6b4ed28cb71837ca1553d9ff5 Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 01:11:08 +0100
Subject: [PATCH 04/12] Refactor: Update URLParameters handling in set_variable
 function

- Replaced serde_json::Map with a custom URLParameters struct for better management of URL parameters.
- Introduced methods for handling single and vector values in URLParameters.
- Updated tests to reflect changes in the set_variable function's behavior.
---
 .../database/sqlpage_functions/functions.rs   | 19 ++--
 .../url_parameter_deserializer.rs             | 91 ++++++++++++++-----
 tests/components/mod.rs                       |  6 +-
 3 files changed, 74 insertions(+), 42 deletions(-)

diff --git a/src/webserver/database/sqlpage_functions/functions.rs b/src/webserver/database/sqlpage_functions/functions.rs
index 0eaf4f76..eefbbc2f 100644
--- a/src/webserver/database/sqlpage_functions/functions.rs
+++ b/src/webserver/database/sqlpage_functions/functions.rs
@@ -618,26 +618,21 @@ async fn set_variable<'a>(
     name: Cow<'a, str>,
     value: Option<Cow<'a, str>>,
 ) -> anyhow::Result<String> {
-    let mut params_map = serde_json::Map::with_capacity(context.url_params.len() + 1);
+    let mut params = URLParameters::new();
 
     for (k, v) in &context.url_params {
-        params_map.insert(k.clone(), serde_json::to_value(v)?);
+        if k == &name {
+            continue;
+        }
+        params.push_single_or_vec(k, v.clone());
     }
 
     if let Some(value) = value {
-        params_map.insert(
-            name.into_owned(),
-            serde_json::Value::String(value.into_owned()),
-        );
-    } else {
-        params_map.remove(&*name);
+        params.push_single_or_vec(&name, SingleOrVec::Single(value.into_owned()));
     }
 
-    let json_val = serde_json::Value::Object(params_map);
-    let encoded: URLParameters = serde_json::from_str(&json_val.to_string())?;
-
     let mut url = context.path.clone();
-    let encoded_str = encoded.get();
+    let encoded_str = params.get();
     if !encoded_str.is_empty() {
         url.push('?');
         url.push_str(encoded_str);
diff --git a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
index 74d3b3ed..e4eb0049 100644
--- a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
+++ b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
@@ -1,3 +1,4 @@
+use crate::webserver::single_or_vec::SingleOrVec;
 use percent_encoding::{percent_encode, NON_ALPHANUMERIC};
 use serde::{Deserialize, Deserializer};
 use serde_json::Value;
@@ -6,7 +7,17 @@ use std::fmt;
 
 pub struct URLParameters(String);
 
+impl Default for URLParameters {
+    fn default() -> Self {
+        Self(String::new())
+    }
+}
+
 impl URLParameters {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
     fn encode_and_push(&mut self, v: &str) {
         let val: Cow<str> = percent_encode(v.as_bytes(), NON_ALPHANUMERIC).into();
         self.0.push_str(&val);
@@ -19,6 +30,49 @@ impl URLParameters {
         self.0.push('=');
         self.encode_and_push(value);
     }
+
+    fn push_array_entry(&mut self, key: &str, value: &str) {
+        if !self.0.is_empty() {
+            self.0.push('&');
+        }
+        self.encode_and_push(key);
+        self.0.push_str("[]=");
+        self.encode_and_push(value);
+    }
+
+    fn push_array(&mut self, key: &str, values: Vec<Value>) {
+        for val in values {
+            let val_str = match val {
+                Value::String(s) => s,
+                other => other.to_string(),
+            };
+            self.push_array_entry(key, &val_str);
+        }
+    }
+
+    pub fn push_single_or_vec(&mut self, key: &str, val: SingleOrVec) {
+        match val {
+            SingleOrVec::Single(v) => self.push_kv(key, &v),
+            SingleOrVec::Vec(v) => {
+                for s in v {
+                    self.push_array_entry(key, &s);
+                }
+            }
+        }
+    }
+
+    fn add_from_json(&mut self, key: &str, raw_json_value: &str) {
+        if let Ok(str_val) = serde_json::from_str::<Option<Cow<str>>>(raw_json_value) {
+            if let Some(str_val) = str_val {
+                self.push_kv(key, &str_val);
+            }
+        } else if let Ok(vec_val) = serde_json::from_str::<Vec<Value>>(raw_json_value) {
+            self.push_array(key, vec_val);
+        } else {
+            self.push_kv(key, raw_json_value);
+        }
+    }
+
     pub fn get(&self) -> &str {
         &self.0
     }
@@ -47,31 +101,7 @@ impl<'de> Deserialize<'de> for URLParameters {
                 while let Some((key, value)) =
                     map.next_entry::<Cow<str>, Cow<serde_json::value::RawValue>>()?
                 {
-                    let value = value.get();
-                    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)
-                    {
-                        for val in vec_val {
-                            if !out.0.is_empty() {
-                                out.0.push('&');
-                            }
-                            out.encode_and_push(&key);
-                            out.0.push_str("[]");
-                            out.0.push('=');
-
-                            let val = match val {
-                                Value::String(s) => s,
-                                other => other.to_string(),
-                            };
-                            out.encode_and_push(&val);
-                        }
-                    } else {
-                        out.push_kv(&key, value);
-                    }
+                    out.add_from_json(&key, value.get());
                 }
 
                 Ok(out)
@@ -136,3 +166,14 @@ fn test_url_parameters_deserializer_issue_879() {
         "name=John%20Doe%20%26%20Son%27s&items[]=1&items[]=item%202%20%26%203&items[]=true&special%5Fchar=%25%26%3D%2B%20"
     );
 }
+
+#[test]
+fn test_push_single_or_vec() {
+    let mut params = URLParameters(String::new());
+    params.push_single_or_vec("k", SingleOrVec::Single("v".to_string()));
+    assert_eq!(params.get(), "k=v");
+
+    let mut params = URLParameters(String::new());
+    params.push_single_or_vec("arr", SingleOrVec::Vec(vec!["a".to_string(), "b".to_string()]));
+    assert_eq!(params.get(), "arr[]=a&arr[]=b");
+}
diff --git a/tests/components/mod.rs b/tests/components/mod.rs
index b2d44546..4c6364d6 100644
--- a/tests/components/mod.rs
+++ b/tests/components/mod.rs
@@ -5,12 +5,8 @@ use crate::common::get_request_to;
 
 #[actix_web::test]
 async fn test_overwrite_variable() -> actix_web::Result<()> {
-    let req = get_request_to("/tests/sql_test_files/it_works_set_variable.sql")
+    let req = get_request_to("/tests/sql_test_files/it_works_set_variable_nomssql.sql")
         .await?
-        .set_form(std::collections::HashMap::<&str, &str>::from_iter([(
-            "what_does_it_do",
-            "does not overwrite variables",
-        )]))
         .to_srv_request();
     let resp = main_handler(req).await?;
 

From 0786df0bf06f7eb04ad3097c3044ace9573ce7bb Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 10:50:55 +0100
Subject: [PATCH 05/12] cargo fmt

---
 .../database/sqlpage_functions/url_parameter_deserializer.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
index e4eb0049..bf8160d4 100644
--- a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
+++ b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
@@ -174,6 +174,9 @@ fn test_push_single_or_vec() {
     assert_eq!(params.get(), "k=v");
 
     let mut params = URLParameters(String::new());
-    params.push_single_or_vec("arr", SingleOrVec::Vec(vec!["a".to_string(), "b".to_string()]));
+    params.push_single_or_vec(
+        "arr",
+        SingleOrVec::Vec(vec!["a".to_string(), "b".to_string()]),
+    );
     assert_eq!(params.get(), "arr[]=a&arr[]=b");
 }

From 0d44e3378824f019a6d32538d79d01bd3eb23d84 Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 10:56:53 +0100
Subject: [PATCH 06/12] clippy

---
 .../sqlpage_functions/url_parameter_deserializer.rs        | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
index bf8160d4..cefcde50 100644
--- a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
+++ b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
@@ -5,14 +5,9 @@ use serde_json::Value;
 use std::borrow::Cow;
 use std::fmt;
 
+#[derive(Default)]
 pub struct URLParameters(String);
 
-impl Default for URLParameters {
-    fn default() -> Self {
-        Self(String::new())
-    }
-}
-
 impl URLParameters {
     pub fn new() -> Self {
         Self::default()

From fd469a9a30cd86db05bac29e212a34f340a92323 Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 11:23:42 +0100
Subject: [PATCH 07/12] retsore set var test

---
 tests/sql_test_files/it_works_set_variable.sql | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 tests/sql_test_files/it_works_set_variable.sql

diff --git a/tests/sql_test_files/it_works_set_variable.sql b/tests/sql_test_files/it_works_set_variable.sql
new file mode 100644
index 00000000..e9ac8286
--- /dev/null
+++ b/tests/sql_test_files/it_works_set_variable.sql
@@ -0,0 +1,2 @@
+set what_does_it_do = 'wo' || 'rks';
+select 'text' as component, 'It ' || $what_does_it_do || ' !' as contents;

From cc27af60a722e08ff9bb03ce658f10b7863b9634 Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 11:28:14 +0100
Subject: [PATCH 08/12] remove redundant test

---
 tests/components/mod.rs | 21 ---------------------
 tests/mod.rs            |  1 -
 2 files changed, 22 deletions(-)
 delete mode 100644 tests/components/mod.rs

diff --git a/tests/components/mod.rs b/tests/components/mod.rs
deleted file mode 100644
index 4c6364d6..00000000
--- a/tests/components/mod.rs
+++ /dev/null
@@ -1,21 +0,0 @@
-use actix_web::{http::StatusCode, test};
-use sqlpage::webserver::http::main_handler;
-
-use crate::common::get_request_to;
-
-#[actix_web::test]
-async fn test_overwrite_variable() -> actix_web::Result<()> {
-    let req = get_request_to("/tests/sql_test_files/it_works_set_variable_nomssql.sql")
-        .await?
-        .to_srv_request();
-    let resp = main_handler(req).await?;
-
-    assert_eq!(resp.status(), StatusCode::OK);
-    let body = test::read_body(resp).await;
-    let body_str = String::from_utf8(body.to_vec()).unwrap();
-    assert!(
-        body_str.contains("It works !"),
-        "{body_str}\nexpected to contain: It works !"
-    );
-    Ok(())
-}
diff --git a/tests/mod.rs b/tests/mod.rs
index aeaf5dc9..78672178 100644
--- a/tests/mod.rs
+++ b/tests/mod.rs
@@ -1,6 +1,5 @@
 mod basic;
 mod common;
-mod components;
 mod core;
 mod data_formats;
 mod errors;

From a59a391446999dee42c168ab75dac2af1648839e Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 11:28:52 +0100
Subject: [PATCH 09/12] ensure set_variable only takes into account GET
 variables, not SET

---
 tests/sql_test_files/it_works_set_variable_null.sql | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/sql_test_files/it_works_set_variable_null.sql b/tests/sql_test_files/it_works_set_variable_null.sql
index 471ea6c6..3d2f8ac6 100644
--- a/tests/sql_test_files/it_works_set_variable_null.sql
+++ b/tests/sql_test_files/it_works_set_variable_null.sql
@@ -1,5 +1,5 @@
-set url = sqlpage.set_variable('x', null);
 set path = sqlpage.path();
+set url = sqlpage.set_variable('x', null);
 select 'text' as component,
     case
         when $url = $path THEN 'It works !'

From 7a65f880b57e6da2a3b3876cce563a50e24cee79 Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 11:46:15 +0100
Subject: [PATCH 10/12] factor url parameter setting code

---
 .../database/sqlpage_functions/functions.rs     | 12 ++----------
 .../url_parameter_deserializer.rs               | 17 +++++++++++++----
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/src/webserver/database/sqlpage_functions/functions.rs b/src/webserver/database/sqlpage_functions/functions.rs
index eefbbc2f..f8d04bc5 100644
--- a/src/webserver/database/sqlpage_functions/functions.rs
+++ b/src/webserver/database/sqlpage_functions/functions.rs
@@ -377,11 +377,7 @@ async fn link<'a>(
         let encoded = serde_json::from_str::<URLParameters>(&parameters).with_context(|| {
             format!("link: invalid URL parameters: not a valid json object:\n{parameters}")
         })?;
-        let encoded_str = encoded.get();
-        if !encoded_str.is_empty() {
-            url.push('?');
-            url.push_str(encoded_str);
-        }
+        encoded.append_to_url(&mut url);
     }
     if let Some(hash) = hash {
         url.push('#');
@@ -632,11 +628,7 @@ async fn set_variable<'a>(
     }
 
     let mut url = context.path.clone();
-    let encoded_str = params.get();
-    if !encoded_str.is_empty() {
-        url.push('?');
-        url.push_str(encoded_str);
-    }
+    params.append_to_url(&mut url);
 
     Ok(url)
 }
diff --git a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
index cefcde50..c6d54180 100644
--- a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
+++ b/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
@@ -68,8 +68,11 @@ impl URLParameters {
         }
     }
 
-    pub fn get(&self) -> &str {
-        &self.0
+    pub fn append_to_url(&self, url: &mut String) {
+        if !self.0.is_empty() {
+            url.push('?');
+            url.push_str(&self.0);
+        }
     }
 }
 
@@ -107,6 +110,12 @@ impl<'de> Deserialize<'de> for URLParameters {
     }
 }
 
+impl std::fmt::Display for URLParameters {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
 #[test]
 fn test_url_parameters_deserializer() {
     use serde_json::json;
@@ -166,12 +175,12 @@ fn test_url_parameters_deserializer_issue_879() {
 fn test_push_single_or_vec() {
     let mut params = URLParameters(String::new());
     params.push_single_or_vec("k", SingleOrVec::Single("v".to_string()));
-    assert_eq!(params.get(), "k=v");
+    assert_eq!(params.to_string(), "k=v");
 
     let mut params = URLParameters(String::new());
     params.push_single_or_vec(
         "arr",
         SingleOrVec::Vec(vec!["a".to_string(), "b".to_string()]),
     );
-    assert_eq!(params.get(), "arr[]=a&arr[]=b");
+    assert_eq!(params.to_string(), "arr[]=a&arr[]=b");
 }

From 544771d1174e64f5f77cb55ed50185b0b6acba7b Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 11:46:21 +0100
Subject: [PATCH 11/12] v0.40

---
 CHANGELOG.md | 8 +++-----
 Cargo.lock   | 2 +-
 Cargo.toml   | 2 +-
 3 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85fcb39d..7bd70d5a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # CHANGELOG.md
 
-## unrelease
+## 0.40.0 (unreleased)
  - **New Function**: `sqlpage.set_variable(name, value)`
    - Returns a URL with the specified variable set to the given value, preserving other existing variables.
    - This is a shorthand for `sqlpage.link(sqlpage.path(), json_patch(sqlpage.variables('get'), json_object(name, value)))`.
@@ -9,15 +9,13 @@
      - **What changed**: Previously, `$x` would return a POST parameter value if no GET parameter named `x` existed.
      - **Fix**: Replace `$x` with `:x` when you need to access form field values.
      - **Example**: Change `SELECT $username` to `SELECT :username` when reading form submissions.
-   - **BREAKING**: `SET $name` no longer overwrites GET (URL) parameters when a URL parameter with the same name exists.
+   - **BREAKING**: `SET $name` no longer makes GET (URL) parameters inaccessible when a URL parameter with the same name exists.
      - **What changed**: `SET $name = 'value'` would previously overwrite the URL parameter `$name`. Now it creates an independent SET variable that shadows the URL parameter.
      - **Fix**: This is generally the desired behavior. If you need to access the original URL parameter after setting a variable with the same name, extract it from the JSON returned by `sqlpage.variables('get')`.
      - **Example**: If your URL is `page.sql?name=john`, and you do `SET $name = 'modified'`, then:
        - `$name` will be `'modified'` (the SET variable)
        - The original URL parameter is still preserved and accessible:
-         - PostgreSQL: `sqlpage.variables('get')->>'name'` returns `'john'`
-         - SQLite: `json_extract(sqlpage.variables('get'), '$.name')` returns `'john'`
-         - MySQL: `JSON_UNQUOTE(JSON_EXTRACT(sqlpage.variables('get'), '$.name'))` returns `'john'`
+         - `sqlpage.variables('get')->>'name'` returns `'john'`
    - **New behavior**: Variable lookup now follows this precedence:
      - `$variable` checks SET variables first, then URL parameters
      - `:variable` checks SET variables first, then POST parameters  
diff --git a/Cargo.lock b/Cargo.lock
index de81defc..a8b0326d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4221,7 +4221,7 @@ dependencies = [
 
 [[package]]
 name = "sqlpage"
-version = "0.39.1"
+version = "0.40.0"
 dependencies = [
  "actix-multipart",
  "actix-rt",
diff --git a/Cargo.toml b/Cargo.toml
index 37fd1380..8cfd5ea1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "sqlpage"
-version = "0.39.1"
+version = "0.40.0"
 edition = "2021"
 description = "Build data user interfaces entirely in SQL. A web server that takes .sql files and formats the query result using pre-made configurable professional-looking components."
 keywords = ["web", "sql", "framework"]

From f62cd704d04e6d08567abd3afdf494818be0b912 Mon Sep 17 00:00:00 2001
From: lovasoa <contact@ophir.dev>
Date: Mon, 24 Nov 2025 12:37:10 +0100
Subject: [PATCH 12/12] sqlpage.set_variable links to "?" when no parameter is
 present

- Renamed URLParameters module for clarity and removed the deprecated url_parameter_deserializer.
- Updated the set_variable function to return parameters directly instead of appending to a URL.
- Adjusted related function calls to reflect changes in URL parameter management.
---
 CHANGELOG.md                                  |  1 +
 .../database/sqlpage_functions/functions.rs   |  9 ++--
 .../database/sqlpage_functions/mod.rs         |  2 +-
 ...eter_deserializer.rs => url_parameters.rs} | 49 +++++++++++++------
 .../it_works_set_variable_func.sql            |  7 +++
 .../it_works_set_variable_func_null.sql       |  6 +++
 .../it_works_set_variable_func_replace.sql    |  6 +++
 .../it_works_set_variable_nomssql.sql         | 10 ----
 .../it_works_set_variable_null.sql            |  7 ---
 .../it_works_set_variable_replace.sql         |  7 ---
 10 files changed, 57 insertions(+), 47 deletions(-)
 rename src/webserver/database/sqlpage_functions/{url_parameter_deserializer.rs => url_parameters.rs} (80%)
 create mode 100644 tests/sql_test_files/it_works_set_variable_func.sql
 create mode 100644 tests/sql_test_files/it_works_set_variable_func_null.sql
 create mode 100644 tests/sql_test_files/it_works_set_variable_func_replace.sql
 delete mode 100644 tests/sql_test_files/it_works_set_variable_nomssql.sql
 delete mode 100644 tests/sql_test_files/it_works_set_variable_null.sql
 delete mode 100644 tests/sql_test_files/it_works_set_variable_replace.sql

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7bd70d5a..9c4353a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 # CHANGELOG.md
 
 ## 0.40.0 (unreleased)
+ - Fixed a bug in `sqlpage.link`: a link with no path (link to the current page) and no url parameter now works as expected. It used to keep the existing url parameters instead of removing them. `sqlpage.link('', '{}')` now returns `'?'` instead of the empty string.
  - **New Function**: `sqlpage.set_variable(name, value)`
    - Returns a URL with the specified variable set to the given value, preserving other existing variables.
    - This is a shorthand for `sqlpage.link(sqlpage.path(), json_patch(sqlpage.variables('get'), json_object(name, value)))`.
diff --git a/src/webserver/database/sqlpage_functions/functions.rs b/src/webserver/database/sqlpage_functions/functions.rs
index f8d04bc5..450a85b8 100644
--- a/src/webserver/database/sqlpage_functions/functions.rs
+++ b/src/webserver/database/sqlpage_functions/functions.rs
@@ -2,7 +2,7 @@ use super::{ExecutionContext, RequestInfo};
 use crate::webserver::{
     database::{
         blob_to_data_url::vec_to_data_uri_with_mime, execute_queries::DbConn,
-        sqlpage_functions::url_parameter_deserializer::URLParameters,
+        sqlpage_functions::url_parameters::URLParameters,
     },
     http_client::make_http_client,
     request_variables::ParamMap,
@@ -377,7 +377,7 @@ async fn link<'a>(
         let encoded = serde_json::from_str::<URLParameters>(&parameters).with_context(|| {
             format!("link: invalid URL parameters: not a valid json object:\n{parameters}")
         })?;
-        encoded.append_to_url(&mut url);
+        encoded.append_to_path(&mut url);
     }
     if let Some(hash) = hash {
         url.push('#');
@@ -627,10 +627,7 @@ async fn set_variable<'a>(
         params.push_single_or_vec(&name, SingleOrVec::Single(value.into_owned()));
     }
 
-    let mut url = context.path.clone();
-    params.append_to_url(&mut url);
-
-    Ok(url)
+    Ok(params.with_empty_path())
 }
 
 #[tokio::test]
diff --git a/src/webserver/database/sqlpage_functions/mod.rs b/src/webserver/database/sqlpage_functions/mod.rs
index 8734c38e..27dc6c07 100644
--- a/src/webserver/database/sqlpage_functions/mod.rs
+++ b/src/webserver/database/sqlpage_functions/mod.rs
@@ -2,7 +2,7 @@ mod function_definition_macro;
 mod function_traits;
 pub(super) mod functions;
 mod http_fetch_request;
-mod url_parameter_deserializer;
+mod url_parameters;
 
 use sqlparser::ast::FunctionArg;
 
diff --git a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs b/src/webserver/database/sqlpage_functions/url_parameters.rs
similarity index 80%
rename from src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
rename to src/webserver/database/sqlpage_functions/url_parameters.rs
index c6d54180..1e30cae3 100644
--- a/src/webserver/database/sqlpage_functions/url_parameter_deserializer.rs
+++ b/src/webserver/database/sqlpage_functions/url_parameters.rs
@@ -10,26 +10,28 @@ pub struct URLParameters(String);
 
 impl URLParameters {
     pub fn new() -> Self {
-        Self::default()
+        Self(String::new())
     }
 
     fn encode_and_push(&mut self, v: &str) {
         let val: Cow<str> = percent_encode(v.as_bytes(), NON_ALPHANUMERIC).into();
         self.0.push_str(&val);
     }
+
+    fn start_new_pair(&mut self) {
+        let char = if self.0.is_empty() { '?' } else { '&' };
+        self.0.push(char);
+    }
+
     fn push_kv(&mut self, key: &str, value: &str) {
-        if !self.0.is_empty() {
-            self.0.push('&');
-        }
+        self.start_new_pair();
         self.encode_and_push(key);
         self.0.push('=');
         self.encode_and_push(value);
     }
 
     fn push_array_entry(&mut self, key: &str, value: &str) {
-        if !self.0.is_empty() {
-            self.0.push('&');
-        }
+        self.start_new_pair();
         self.encode_and_push(key);
         self.0.push_str("[]=");
         self.encode_and_push(value);
@@ -68,9 +70,18 @@ impl URLParameters {
         }
     }
 
-    pub fn append_to_url(&self, url: &mut String) {
-        if !self.0.is_empty() {
-            url.push('?');
+    pub fn with_empty_path(self) -> String {
+        if self.0.is_empty() {
+            "?".to_string() // Link to the current page without parameters
+        } else {
+            self.0 // Link to the current page with specific parameters
+        }
+    }
+
+    pub fn append_to_path(self, url: &mut String) {
+        if url.is_empty() {
+            *url = self.with_empty_path();
+        } else {
             url.push_str(&self.0);
         }
     }
@@ -116,6 +127,12 @@ impl std::fmt::Display for URLParameters {
     }
 }
 
+impl From<URLParameters> for String {
+    fn from(value: URLParameters) -> Self {
+        value.0
+    }
+}
+
 #[test]
 fn test_url_parameters_deserializer() {
     use serde_json::json;
@@ -128,7 +145,7 @@ fn test_url_parameters_deserializer() {
     let url_parameters: URLParameters = serde_json::from_value(json).unwrap();
     assert_eq!(
         url_parameters.0,
-        "x=hello%20world&num=123&arr[]=1&arr[]=2&arr[]=3"
+        "?x=hello%20world&num=123&arr[]=1&arr[]=2&arr[]=3"
     );
 }
 
@@ -141,7 +158,7 @@ fn test_url_parameters_null() {
     });
 
     let url_parameters: URLParameters = serde_json::from_value(json).unwrap();
-    assert_eq!(url_parameters.0, "x=hello");
+    assert_eq!(url_parameters.0, "?x=hello");
 }
 
 #[test]
@@ -152,7 +169,7 @@ fn test_url_parameters_deserializer_special_chars() {
     });
 
     let url_parameters: URLParameters = serde_json::from_value(json).unwrap();
-    assert_eq!(url_parameters.0, "chars[]=%0A&chars[]=%20&chars[]=%22");
+    assert_eq!(url_parameters.0, "?chars[]=%0A&chars[]=%20&chars[]=%22");
 }
 
 #[test]
@@ -167,7 +184,7 @@ fn test_url_parameters_deserializer_issue_879() {
     let url_parameters: URLParameters = serde_json::from_value(json).unwrap();
     assert_eq!(
         url_parameters.0,
-        "name=John%20Doe%20%26%20Son%27s&items[]=1&items[]=item%202%20%26%203&items[]=true&special%5Fchar=%25%26%3D%2B%20"
+        "?name=John%20Doe%20%26%20Son%27s&items[]=1&items[]=item%202%20%26%203&items[]=true&special%5Fchar=%25%26%3D%2B%20"
     );
 }
 
@@ -175,12 +192,12 @@ fn test_url_parameters_deserializer_issue_879() {
 fn test_push_single_or_vec() {
     let mut params = URLParameters(String::new());
     params.push_single_or_vec("k", SingleOrVec::Single("v".to_string()));
-    assert_eq!(params.to_string(), "k=v");
+    assert_eq!(params.to_string(), "?k=v");
 
     let mut params = URLParameters(String::new());
     params.push_single_or_vec(
         "arr",
         SingleOrVec::Vec(vec!["a".to_string(), "b".to_string()]),
     );
-    assert_eq!(params.to_string(), "arr[]=a&arr[]=b");
+    assert_eq!(params.to_string(), "?arr[]=a&arr[]=b");
 }
diff --git a/tests/sql_test_files/it_works_set_variable_func.sql b/tests/sql_test_files/it_works_set_variable_func.sql
new file mode 100644
index 00000000..b3b2771a
--- /dev/null
+++ b/tests/sql_test_files/it_works_set_variable_func.sql
@@ -0,0 +1,7 @@
+set url = sqlpage.set_variable('y', '2');
+
+select 'text' as component,
+    case $url
+        when '?x=1&y=2' THEN 'It works !'
+        else 'It failed ! Expected ?x=1&y=2 but got ' || coalesce($url, 'NULL')
+    end as contents;
\ No newline at end of file
diff --git a/tests/sql_test_files/it_works_set_variable_func_null.sql b/tests/sql_test_files/it_works_set_variable_func_null.sql
new file mode 100644
index 00000000..21800dc4
--- /dev/null
+++ b/tests/sql_test_files/it_works_set_variable_func_null.sql
@@ -0,0 +1,6 @@
+set url = sqlpage.set_variable('x', null);
+select 'text' as component,
+    case $url
+        when '?' THEN 'It works !'
+        else 'It failed ! Expected "?" but got ' || coalesce('"' || $url || '"', 'NULL')
+    end as contents;
diff --git a/tests/sql_test_files/it_works_set_variable_func_replace.sql b/tests/sql_test_files/it_works_set_variable_func_replace.sql
new file mode 100644
index 00000000..6d71a44b
--- /dev/null
+++ b/tests/sql_test_files/it_works_set_variable_func_replace.sql
@@ -0,0 +1,6 @@
+set url = sqlpage.set_variable('x', '2');
+select 'text' as component,
+    case $url
+        when '?x=2' THEN 'It works !'
+        else 'It failed ! Expected ?x=2 but got ' || $url
+    end as contents;
diff --git a/tests/sql_test_files/it_works_set_variable_nomssql.sql b/tests/sql_test_files/it_works_set_variable_nomssql.sql
deleted file mode 100644
index 24793b1d..00000000
--- a/tests/sql_test_files/it_works_set_variable_nomssql.sql
+++ /dev/null
@@ -1,10 +0,0 @@
-set url = sqlpage.set_variable('y', '2');
-set path = sqlpage.path();
-set x = json_extract(sqlpage.variables('get'), '$.x');
-
-select 'text' as component,
-    case
-        when $x is not null AND ($url = $path || '?x=' || $x || '&y=2' OR $url = $path || '?y=2&x=' || $x) THEN 'It works !'
-        when $x is null AND $url = $path || '?y=2' THEN 'It works !'
-        else 'error: ' || $url
-    end as contents;
diff --git a/tests/sql_test_files/it_works_set_variable_null.sql b/tests/sql_test_files/it_works_set_variable_null.sql
deleted file mode 100644
index 3d2f8ac6..00000000
--- a/tests/sql_test_files/it_works_set_variable_null.sql
+++ /dev/null
@@ -1,7 +0,0 @@
-set path = sqlpage.path();
-set url = sqlpage.set_variable('x', null);
-select 'text' as component,
-    case
-        when $url = $path THEN 'It works !'
-        else 'error: ' || $url
-    end as contents;
diff --git a/tests/sql_test_files/it_works_set_variable_replace.sql b/tests/sql_test_files/it_works_set_variable_replace.sql
deleted file mode 100644
index 9ad99b85..00000000
--- a/tests/sql_test_files/it_works_set_variable_replace.sql
+++ /dev/null
@@ -1,7 +0,0 @@
-set url = sqlpage.set_variable('x', '2');
-set path = sqlpage.path();
-select 'text' as component,
-    case
-        when $url = $path || '?x=2' THEN 'It works !'
-        else 'error: ' || $url
-    end as contents;