feat(intl): support optional inputs

Author: innocenzi

packages/intl/src/MessageFormat/Formatter/MessageFormatter.php

@@ -82,7 +82,18 @@ private function formatMessage(MessageNode $message): string
                     $variableName = $expression->variable->name->name;
 
                     if (! array_key_exists($variableName, $this->variables)) {
-                        throw new FormattingException("Required input variable `{$variableName}` not provided.");
+                        if ($declaration->optional) {
+                            $parameters = $this->evaluateOptions($expression->function?->options ?? []);
+
+                            $this->variables[$variableName] = new LocalVariable(
+                                identifier: $variableName,
+                                value: $parameters['default'],
+                                function: $this->getSelectorFunction((string) $expression->function?->identifier),
+                                parameters: $parameters,
+                            );
+                        } else {
+                            throw new FormattingException("Required input variable `{$variableName}` not provided.");
+                        }
                     }
 
                     if ($expression->function instanceof FunctionCall) {

packages/intl/src/MessageFormat/Functions/BooleanFunction.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace Tempest\Intl\MessageFormat\Functions;
+
+use Tempest\Intl\MessageFormat\SelectorFunction;
+
+final class BooleanFunction implements SelectorFunction
+{
+    public string $name = 'boolean';
+
+    public function match(string $key, mixed $value, array $parameters): bool
+    {
+        return match ((bool) $value) {
+            true => in_array($key, ['true', true], strict: true),
+            false => in_array($key, ['false', false], strict: true),
+        };
+    }
+}

packages/intl/src/MessageFormat/Functions/StringFunction.php

@@ -19,7 +19,7 @@ public function match(string $key, mixed $value, array $parameters): bool
 
     public function format(mixed $value, array $parameters): FormattedValue
     {
-        $string = Str\parse($value, default: '');
+        $string = Str\parse($value, default: Arr\get_by_key($parameters, 'default', default: ''));
         $formatted = match (Arr\get_by_key($parameters, 'style')) {
             'uppercase', 'upper' => Str\to_upper_case($string),
             'lowercase', 'lower' => Str\to_lower_case($string),

packages/intl/src/MessageFormat/Parser/MessageFormatParser.php

@@ -125,7 +125,14 @@ private function parseInputDeclaration(): InputDeclaration
         $this->consumeKeyword('.input');
         $this->consumeRequiredWhitespace();
 
-        return new InputDeclaration($this->parseVariableExpression());
+        $expression = $this->parseVariableExpression();
+
+        $optional = (bool) array_find(
+            array: $expression->function?->options ?? [],
+            callback: fn (Option $option) => $option->identifier->name === 'default' && ! is_null($option->value->value),
+        );
+
+        return new InputDeclaration($expression, $optional);
     }
 
     private function parseLocalDeclaration(): LocalDeclaration

packages/intl/src/MessageFormat/Parser/Node/Declaration/InputDeclaration.php

@@ -8,5 +8,6 @@
 {
     public function __construct(
         public VariableExpression $expression,
+        public bool $optional,
     ) {}
 }

packages/intl/tests/FormatterTest.php

@@ -94,6 +94,25 @@ public function test_match_number(int $count, string $expected): void
         $this->assertSame($expected, $value);
     }
 
+    public function test_default_input(): void
+    {
+        $formatter = new MessageFormatter([]);
+
+        $value = $formatter->format(<<<'TXT'
+        .input {$field :string default=unknown}
+        field is {$field}
+        TXT);
+
+        $this->assertSame('field is unknown', $value);
+
+        $value = $formatter->format(<<<'TXT'
+        .input {$field :string default=unknown}
+        field is {$field}
+        TXT, field: 'here');
+
+        $this->assertSame('field is here', $value);
+    }
+
     public function test_unquoted_text(): void
     {
         $formatter = new MessageFormatter();