form select: loose equality testing for option values

the form component now considers numbers and their string representation as equal when comparing the `value` parameter and the values from the `options` parameter in dropdowns

see #1002

Author: lovasoa

CHANGELOG.md

@@ -22,6 +22,16 @@
      ```
  - When a sql file is saved with the wrong character encoding (not UTF8), SQLPage now displays a helpful error messages that points to exactly where in the file the problem is.
  - More visual error messages: errors that occured before (such as file access issues) used to generate plain text messages that looked scary to non-technical users. All errors are now displayed nicely in the browser.
+ - The form component now considers numbers and their string representation as equal when comparing the `value` parameter and the values from the `options` parameter in dropdowns. This makes it easier to use variables (which are always strings) in the value parameter in order to preserve a dropdown field value across page reloads. The following is now valid:
+    - ```sql
+      select 'form' as component;
+      select 
+          'select' as type,
+          true as create_new,
+          true as dropdown,
+          '2' as value, -- passed as text even if the option values are passed as integers
+          '[{"label": "A", "value": 1}, {"label": "B", "value": 2}]' as options;
+      ```
 
 ## v0.36.1
  - Fix regression introduced in v0.36.0: PostgreSQL money values showed as 0.0

sqlpage/templates/form.handlebars

@@ -104,7 +104,7 @@
                         >
                         {{#if empty_option}}<option value="">{{empty_option}}</option>{{/if}}
                         {{#each (parse_json options)}}
-                            <option value="{{value}}" {{#if (or (eq ../value value) selected)}}selected{{/if}}>{{label}}</option>
+                            <option value="{{value}}" {{#if (or (loose_eq ../value value) selected)}}selected{{/if}}>{{label}}</option>
                         {{/each}}
                         </select>
                     {{else}}

src/template_helpers.rs

@@ -37,6 +37,7 @@ pub fn register_all_helpers(h: &mut Handlebars<'_>, config: &AppConfig) {
     register_helper(h, "plus", plus_helper as HH);
     register_helper(h, "minus", minus_helper as HH);
     h.register_helper("sum", Box::new(sum_helper));
+    register_helper(h, "loose_eq", loose_eq_helper as HH);
     register_helper(h, "starts_with", starts_with_helper as HH);
 
     // to_array: convert a value to a single-element array. If the value is already an array, return it as-is.
@@ -472,6 +473,16 @@ fn sum_helper<'reg, 'rc>(
     Ok(())
 }
 
+/// Compare two values loosely, i.e. treat all values as strings. (42 == "42")
+fn loose_eq_helper(a: &JsonValue, b: &JsonValue) -> JsonValue {
+    match (a, b) {
+        (JsonValue::String(a), JsonValue::String(b)) => a == b,
+        (JsonValue::String(a), non_str) => a == &non_str.to_string(),
+        (non_str, JsonValue::String(b)) => &non_str.to_string() == b,
+        (a, b) => a == b,
+    }
+    .into()
+}
 /// Helper that returns the first argument with the given truthiness, or the last argument if none have it.
 /// Equivalent to a && b && c && ... if the truthiness is false,
 /// or a || b || c || ... if the truthiness is true.