Add ability to check for non-existant properties without using except…

…ions

src/main/php/web/Environment.class.php

@@ -87,10 +87,11 @@ public function variable($name) {
    * Gets properties
    *
    * @param  string $name
+   * @param  bool $optional Whether to return or throw if properties aren't found.
    * @return util.PropertyAccess
    * @throws lang.ElementNotFoundException
    */
-  public function properties($name) {
+  public function properties($name, $optional= false) {
     $expand= function($name) { return $this->{$name}(); };
     $found= [];
     foreach ($this->sources as $source) {
@@ -99,15 +100,20 @@ public function properties($name) {
       }
     }
 
-    switch (sizeof($found)) {
-      case 1: return $found[0];
-      case 0: throw new ElementNotFoundException(sprintf(
-        'Cannot find properties "%s" in any of %s',
-        $name,
-        Objects::stringOf($this->sources)
-      ));
-      default: return new CompositeProperties($found);
+    $n= sizeof($found);
+    if ($n > 1) {
+      return new CompositeProperties($found);
+    } else if (1 === $n) {
+      return $found[0];
+    } else if ($optional) {
+      return null;
     }
+
+    throw new ElementNotFoundException(sprintf(
+      'Cannot find properties "%s" in any of %s',
+      $name,
+      Objects::stringOf($this->sources)
+    ));
   }
 
   /** @return string[] */

src/test/php/web/unittest/EnvironmentTest.class.php

@@ -91,10 +91,15 @@ public function non_existant_properties() {
   }
 
   #[Test]
-  public function properties() {
+  public function optional_non_existant_properties() {
+    $this->assertNull((new Environment('dev', '.', 'static', []))->properties('inject', true));
+  }
+
+  #[Test, Values([true, false])]
+  public function properties($optional) {
     $prop= new Properties('inject.ini');
     $environment= new Environment('dev', '.', 'static', [new RegisteredPropertySource('inject', $prop)]);
-    $this->assertEquals($prop, $environment->properties('inject'));
+    $this->assertEquals($prop, $environment->properties('inject', $optional));
   }
 
   #[Test]