Add typed data example code

This example looks good to me, and once in should allow for some refactoring of the field_example RGB field to use this new Typed Data. I'm assuming that refactoring is beyond the scope of this issue but I'm marking it as Reviewed & Tested since it looks like a solid example to me.

If there is anything I can do to help move the consideration of this patch along please let me know.

Would be nice to get the tests passing...

At a glance I noticed there's no functional tests of paths created for the example, because there aren't any paths. So we need a description page you can read when it's installed.

Other things to add at the checklist here: #2209627: [meta] Module Checklist for Examples

Also needs a ton of inline comments. For instance, this docblock should explain what all the annotation is doing:

+++ b/typed_data_example/src/Plugin/DataType/Color.php
@@ -0,0 +1,49 @@
+/**
+ * @DataType(
+ *   id = "typed_data_example_color",
+ *   label = @Translation("Color"),
+ *   definition_class = "\Drupal\typed_data_example\TypedData\ColorDefinition",
+ *   list_class = "\Drupal\typed_data_example\Plugin\DataType\ExampleColorItemList"
+ * )
+ */
+class Color extends Map {

Patch still applies.. Running the testbot.

The default branch is 3.x-dev which is Drupal 9 compatible. And I would port this to Drupal 9. :)

Rerolled the patch for 3.x, changes explaining in next comment.

Testing on HEAD is broken. Fixing in #3160118: Fix broken testing on HEAD

>Rerolled the patch for 3.x, changes explaining in next comment.

Interrupted in the middle. Forgot...

1. Moved the module into the subfolder modules

2. +++ b/typed_data_example/typed_data_example.info.yml
   @@ -0,0 +1,7 @@
   +core: 8.x
   

   one line change made for D9

3. +++ b/typed_data_example/typed_data_example.routing.yml
   @@ -0,0 +1,9 @@
   +    _admin_route: TRUE
   ...
   +    _access: TRUE
   

   TRUE should be 'TRUE'

4. HEAD is GREEN again, see https://www.drupal.org/pift-ci-job/1763454

Fix failed tests in #14 and a little improvements below-relevant.

+++ b/modules/typed_data_example/tests/src/Unit/TypedData/ColorDefinitionTest.php
@@ -0,0 +1,30 @@
+   * Assert that properties exist.

Should start with "Tests"

Forgot to upload the patch...

diff --git a/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorSetTest.php b/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorSetTest.php
index 878650a..dffdfc7 100644
--- a/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorSetTest.php
+++ b/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorSetTest.php
@@ -12,7 +12,7 @@ use Drupal\typed_data_example\TypedData\ColorSetDefinition;
 use Prophecy\Argument;
 
 /**
- * Test the ColorSet data type.
+ * Tests the ColorSet data type.
  *
  * @ingroup typed_data_example
  *
@@ -26,7 +26,7 @@ class ColorSetTest extends UnitTestCase {
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
 
     $definition = ColorSetDefinition::create('typed_data_example_color_set');
     $definition->setClass('\Drupal\typed_data_example\Plugin\DataType\ColorSet');
@@ -76,7 +76,7 @@ class ColorSetTest extends UnitTestCase {
   }
 
   /**
-   * Assert that the data type class is returned when getting property.
+   * Tests that the data type class is returned when getting property.
    *
    * @param string $class_name
    *   The class name to test.
@@ -90,7 +90,7 @@ class ColorSetTest extends UnitTestCase {
   }
 
   /**
-   * Get the test parameters for testProperty.
+   * Data provider for testProperty().
    *
    * @return array
    *   An array of test parameters.
diff --git a/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorTest.php b/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorTest.php
index 8c74114..55c289a 100644
--- a/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorTest.php
+++ b/modules/typed_data_example/tests/src/Unit/Plugin/DataType/ColorTest.php
@@ -30,7 +30,7 @@ class ColorTest extends UnitTestCase {
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
 
     // The color definition class is fairly safe to use without mocking.
     $definition = ColorDefinition::create('typed_data_example_color');
diff --git a/modules/typed_data_example/tests/src/Unit/TypedData/ColorSetDefinitionTest.php b/modules/typed_data_example/tests/src/Unit/TypedData/ColorSetDefinitionTest.php
index e0a27af..2c1ccf5 100644
--- a/modules/typed_data_example/tests/src/Unit/TypedData/ColorSetDefinitionTest.php
+++ b/modules/typed_data_example/tests/src/Unit/TypedData/ColorSetDefinitionTest.php
@@ -7,7 +7,7 @@ use Drupal\Tests\UnitTestCase;
 use Drupal\typed_data_example\TypedData\ColorSetDefinition;
 
 /**
- * Test the Example definition.
+ * Tests the ColorSet definition.
  *
  * @ingroup typed_data_example
  *
@@ -19,7 +19,7 @@ class ColorSetDefinitionTest extends UnitTestCase {
   /**
    * {@inheritdoc}
    */
-  protected function setUp() {
+  protected function setUp(): void {
     $typedDataProphecy = $this->prophesize('\Drupal\Core\TypedData\TypedDataManagerInterface');
     $container = new ContainerBuilder();
     $container->set('typed_data_manager', $typedDataProphecy->reveal());
@@ -27,7 +27,7 @@ class ColorSetDefinitionTest extends UnitTestCase {
   }
 
   /**
-   * Assert that properties exist.
+   * Tests that properties exist.
    */
   public function testGetPropertyDefinitions() {
     $definition = new ColorSetDefinition();
diff --git a/modules/typed_data_example/typed_data_example.links.menu.yml b/modules/typed_data_example/typed_data_example.links.menu.yml
index e305d2b..554fa75 100644
--- a/modules/typed_data_example/typed_data_example.links.menu.yml
+++ b/modules/typed_data_example/typed_data_example.links.menu.yml
@@ -1,3 +1,3 @@
 typed_data_example.description:
   title: Typed Data Example
-  route_name: typed_data_example_description
\ No newline at end of file
+  route_name: typed_data_example_description

A few improvements

1. Adding newline at the end of file to typed_data_example.links.menu.yml
2. Adding type hinting to setUp().
3. Tests comments start with "verb".

Tagging Needs issue summary update for what left to do here or leaving all the rest to separate issues.

@jungle thanks for pushing this example forward!
I'm still looking at the code (it's a big patch, sorry!) Meanwhile, I suggest to use more specific file name for the template - `description.html.twig` would be hard to find in a real theme. Something like `typed-data-description.html.twig` maybe?

Other comments:

- it's not clear how to use procedural code from typed_data_example.module. Should this code be moved to a service?
- return values of procedural functions are not used
- description.html.twig is not used anywhere (or I missed it?)
- changes suggested in #19 (defining void return type) are relevant only with PHP7.4, and should be fixed in core classes too, without it static analysis will continue to fail