refactor(components): Load using include_once and call in loader

Instead of expecting each component to call itself, this change calls 
component functions directly in the component loader, simplifying 
component writing. This change also switches to use `include_once` to 
load the component files, potentially speeding things up.

ARCHITECTURE.md

@@ -243,7 +243,7 @@ Besides the templates described above, WordPress themes provide much of their cu
 
 To break up the large page templates described above, some layouts that are re-used are stored in the [`components`](components) directory and included in the main templates using the `component()` method declared in [`functions/component-loader.php`](functions/component-loader.php).
 
-For example, `footer.php` includes a copyright string that updates its date range automatically and is defined in `components/hgnm_copyright.php`. To include a component call `component()` with the component file name as the first argument:
+For example, `footer.php` includes a copyright string that updates its date range automatically and is defined in `components/hgnm_copyright.php`. To include a component, call `component()` with the component file name as the first argument:
 
 ```php
 <?= component('hgnm_copyright') ?>
@@ -258,7 +258,7 @@ If the component needs to be passed additional data, this can be achieved via th
 
 ### Writing a component
 
-A component is a PHP file declaring a function that renders the component and a call to that function. While technically a component is any function, best practice is for a component to return an HTML string. This allows you to pass a component around, for example handing it to another component for use as a child element, only printing its output when needed.
+A component is a PHP file declaring a function that renders the component. While technically a component is any function, best practice is for a component to return an HTML string. This allows you to pass a component around, for example handing it to another component for use as a child element, only printing its output when needed.
 
 The basic skeleton of a component looks like this:
 
@@ -277,18 +277,17 @@ if (!function_exists('pretty_p')) {
         return $html;
     }
 }
-
-// Call the component function and return it
-return pretty_p($opts);
 ```
 
-The second argument passed to `component()` is injected into your component’s scope as `$opts`, so by saving the component as `components/pretty_p.php` we can then use it as follows:
+The function name _must_ match the filename you save the component as, so the above must be saved as `components/pretty_p.php`.
+
+Your component function will be called with the second argument passed to `component()`, so  we can then use the above as follows:
 
 ```php
 <?= component('pretty_p', array( "text" => 'Paragraph text' )); ?>
 ```
 
-**N.B.** the `<?= '...' ?>` PHP tag is shorthand for `<?php echo '...' ?>`
+ℹ️ The `<?= '...' ?>` PHP tag is shorthand for `<?php echo '...' ?>`
 
 
 

components/analytics.php

@@ -18,5 +18,3 @@ function analytics($tracking_code)
 <script async src='https://www.google-analytics.com/analytics.js'></script>";
     }
 }
-
-return analytics($opts);

components/button_link.php

@@ -31,5 +31,3 @@ function button_link($opts)
         return "<a $attribute_string>$inner</a>";
     }
 }
-
-return button_link($opts);

components/colloquium_list.php

@@ -20,5 +20,3 @@ function colloquium_list($opts)
         return $html;
     }
 }
-
-return colloquium_list($opts);

components/colloquium_list_item.php

@@ -82,5 +82,3 @@ function colloquium_list_item($ID)
         return $html;
     }
 }
-
-return colloquium_list_item($opts);

components/colloquium_location_link.php

@@ -23,5 +23,3 @@ function colloquium_location_link(array $opts)
         return $html;
     }
 }
-
-return colloquium_location_link($opts);

components/concert_list_item.php

@@ -80,5 +80,3 @@ function concert_list_item(array $opts)
         return $html;
     }
 }
-
-return concert_list_item($opts);

components/edit_button.php

@@ -12,5 +12,3 @@ function edit_button()
         return '';
     }
 }
-
-return edit_button();

components/hgnm_copyright.php

@@ -29,5 +29,3 @@ function hgnm_copyright()
         return $output;
     }
 }
-
-return hgnm_copyright();

components/icon.php

@@ -22,5 +22,3 @@ function icon($opts)
         return $html;
     }
 }
-
-return icon($opts);

components/member_list.php

@@ -28,5 +28,3 @@ function member_list(array $opts)
         return $html;
     }
 }
-
-return member_list($opts);

components/member_list_item.php

@@ -23,5 +23,3 @@ function member_list_item($opts)
         return $html;
     }
 }
-
-return member_list_item($opts);

components/responsive_embed.php

@@ -13,5 +13,3 @@ function responsive_embed($media)
         return $html;
     }
 }
-
-return responsive_embed($opts);

functions/component-loader.php

@@ -12,6 +12,10 @@ function component($name, $opts = array())
         if (empty($template)) {
             throw new Exception("Template not found at $template_path");
         }
-        return include($template);
+        include_once($template);
+        if (!is_callable($name)) {
+            throw new Exception("$template_path does not declare a function (or function is not named '$name')");
+        }
+        return $name($opts);
     }
 }