Support specifying attributes to DartPad (#5884)

Enables the mechanism for adding a `title` attribute to DartPad code
blocks.

````markdown
```dartpad run="true" title="The classic hello world program in Dart!"
theme="dark"
void main() {
  print('Hello world!');
}
```
````

Contributes to #5251

src/_11ty/plugins/highlight.js

@@ -86,13 +86,16 @@ function _highlight(
   language,
   attributeString,
 ) {
+  const attributes = _parseAttributes(attributeString);
+
   // Specially handle DartPad snippets so that inject_embed can convert them.
-  if (language.includes('-dartpad')) {
-    return `<pre><code data-dartpad="true" data-embed="true" data-theme="light">${markdown.utils.escapeHtml(content)}</code></pre>`;
+  if (language.includes('dartpad')) {
+    const theme = attributes['theme'] ?? 'light';
+    const title = attributes['title'] ?? 'Runnable Dart sample';
+    const runAutomatically = attributes['run'] ?? 'false';
+    return `<pre><code data-dartpad="true" data-embed="true" data-theme="${theme}" title="${title}" data-run="${runAutomatically}">${markdown.utils.escapeHtml(content)}</code></pre>`;
   }
 
-  const attributes = _parseAttributes(attributeString);
-
   const showLineNumbers = 'showLineNumbers' in attributes;
   let startingLineNumber = 0;
   if (showLineNumbers) {

src/content/codelabs/async-await.md

@@ -70,7 +70,7 @@ Before running this example, try to spot the issue --
 what do you think the output will be?
 
 <?code-excerpt "async_await/bin/get_order_sync_bad.dart" remove="Fetching"?>
-```dart:run-dartpad:height-380px:ga_id-incorrect_usage
+```dartpad
 // This example shows how *not* to write asynchronous Dart code.
 
 String createOrderMessage() {
@@ -170,7 +170,7 @@ try to predict which will print first:
 "Large Latte" or "Fetching user order...".
 
 <?code-excerpt "async_await/bin/futures_intro.dart (no-error)"?>
-```dart:run-dartpad:height-300px:ga_id-introducting_futures
+```dartpad
 Future<void> fetchUserOrder() {
   // Imagine that this function is fetching user info from another service or database.
   return Future.delayed(const Duration(seconds: 2), () => print('Large Latte'));
@@ -194,7 +194,7 @@ Run the following example to see how a future completes with an error.
 A bit later you'll learn how to handle the error.
 
 <?code-excerpt "async_await/bin/futures_intro.dart (error)" replace="/Error//g"?>
-```dart:run-dartpad:height-300px:ga_id-completing_with_error
+```dartpad
 Future<void> fetchUserOrder() {
   // Imagine that this function is fetching user info but encounters a bug.
   return Future.delayed(
@@ -375,7 +375,7 @@ within an `async` function body.
 What do you think the output will be?
 
 <?code-excerpt "async_await/bin/async_example.dart" remove="/\/\/ print/"?>
-```dart:run-dartpad:height-530px:ga_id-execution_within_async_function
+```dartpad
 Future<void> printOrderMessage() async {
   print('Awaiting user order...');
   var order = await fetchUserOrder();
@@ -457,7 +457,7 @@ Implement an `async` function `reportLogins()` so that it does the following:
   * Example return value from `reportLogins()`: `"Total number of logins: 57"`
 * Gets the number of logins by calling the provided function `fetchLoginAmount()`.
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-practice_using
+```dartpad theme="dark"
 // Part 1
 // Call the provided async function fetchRole()
 // to return the user role.
@@ -640,7 +640,7 @@ from an asynchronous function.
 What do you think the output will be?
 
 <?code-excerpt "async_await/bin/try_catch.dart"?>
-```dart:run-dartpad:height-530px:ga_id-try_catch
+```dartpad
 Future<void> printOrderMessage() async {
   try {
     print('Awaiting user order...');
@@ -693,7 +693,7 @@ that does the following:
     and
     [Errors.]({{site.dart-api}}/{{site.sdkInfo.channel}}/dart-core/Error-class.html)
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-practice_errors
+```dartpad theme="dark"
 // TODO: Implement changeUsername here.
 changeUsername() {}
 
@@ -861,7 +861,7 @@ Write the following:
   `'<result> Thanks, see you next time'`, where `<result>` is
   the string value returned by calling `logoutUser()`.
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-putting_it_all_together
+```dartpad theme="dark"
 // Part 1
 addHello(String user) {}
 

src/content/codelabs/dart-cheatsheet.md

@@ -48,7 +48,7 @@ The following function takes two integers as parameters.
 Make it return a string containing both integers separated by a space.
 For example, `stringify(2, 3)` should return `'2 3'`.
 
-```dart:run-dartpad:ga_id-string_interpolation
+```dartpad
 String stringify(int x, int y) {
   TODO('Return a formatted string here');
 }
@@ -123,7 +123,7 @@ Try to declare two variables below:
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:ga_id-nullable_variables
+```dartpad
 // TODO: Declare the two variables here
 
 
@@ -192,7 +192,7 @@ to implement the described behavior in the following snippet.
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:height-255px:ga_id-null_aware
+```dartpad
 String? foo = 'a string';
 String? bar; // = null
 
@@ -282,7 +282,7 @@ The following function takes a nullable string as a parameter.
 Try using conditional property access to make it
 return the uppercase version of `str`, or `null` if `str` is `null`.
 
-```dart:run-dartpad:ga_id-conditional-property_access
+```dartpad
 String? upperCaseIt(String? str) {
   // TODO: Try conditionally accessing the `toUpperCase` method here.
 }
@@ -372,7 +372,7 @@ final aListOfBaseType = <BaseType>[SubType(), SubType()];
 
 Try setting the following variables to the indicated values. Replace the existing null values.
 
-```dart:run-dartpad:height-400px:ga_id-collection_literals
+```dartpad
 // Assign this a list containing 'a', 'b', and 'c' in that order:
 final aListOfStrings = null;
 
@@ -502,7 +502,7 @@ bool hasEmpty = aListOfStrings.any((s) => s.isEmpty);
 
 Try finishing the following statements, which use arrow syntax.
 
-```dart:run-dartpad:height-345px:ga_id-arrow_syntax
+```dartpad
 class MyClass {
   int value1 = 2;
   int value2 = 3;
@@ -654,7 +654,7 @@ sets the `anInt`, `aString`, and `aList` properties of a `BigObject`
 to `1`, `'String!'`, and `[3.0]` (respectively)
 and then calls `allDone()`.
 
-```dart:run-dartpad:height-345px:ga_id-cascades
+```dartpad
 class BigObject {
   int anInt = 0;
   String aString = '';
@@ -791,7 +791,7 @@ Add the following:
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:height-240px:ga_id-getters_setters
+```dartpad
 class InvalidPriceException {}
 
 class ShoppingCart {
@@ -948,7 +948,7 @@ Here are some examples of function calls and returned values:
 
 <br>
 
-```dart:run-dartpad:ga_id-optional_positional_parameters
+```dartpad
 String joinWithCommas(int a, [int? b, int? c, int? d, int? e]) {
   return TODO();
 }
@@ -1090,7 +1090,7 @@ then copy its value into `anInt`.
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:height-310px:ga_id-optional_named_parameters
+```dartpad
 class MyDataObject {
   final int anInt;
   final String aString;
@@ -1258,7 +1258,7 @@ then do the following:
 * After everything's caught and handled, call `logger.doneLogging`
   (try using `finally`).
 
-```dart:run-dartpad:height-420px:ga_id-exceptions
+```dartpad
 typedef VoidFunction = void Function();
 
 class ExceptionWithMessage {
@@ -1453,7 +1453,7 @@ all three properties of the class.
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:ga_id-this_constructor
+```dartpad
 class MyClass {
   final int anInt;
   final String aString;
@@ -1568,7 +1568,7 @@ FINALLY: Suggest using https://pub.dev/packages/characters
 if this is a user-entered string.
 {% endcomment %}
 
-```dart:run-dartpad:ga_id-initializer_lists
+```dartpad
 class FirstTwoLetters {
   final String letterOne;
   final String letterTwo;
@@ -1670,7 +1670,7 @@ that sets all three properties to zero.
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:height-240px:ga_id-named_constructors
+```dartpad
 class Color {
   int red;
   int green;
@@ -1766,7 +1766,7 @@ making it do the following:
   create an `IntegerTriple` with the values in order.
 * Otherwise, throw an `Error`.
 
-```dart:run-dartpad:height-415px:ga_id-factory_constructors
+```dartpad
 class IntegerHolder {
   IntegerHolder();
   
@@ -1937,7 +1937,7 @@ default constructor with zeros as the arguments.
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:height-255px:ga_id-redirecting_constructors
+```dartpad
 class Color {
   int red;
   int green;
@@ -2024,7 +2024,7 @@ and create a constant constructor that does the following:
 
 Ignore all initial errors in the DartPad.
 
-```dart:run-dartpad:ga_id-const_constructors
+```dartpad
 class Recipe {
   List<String> ingredients;
   int calories;

src/content/codelabs/iterables.md

@@ -126,7 +126,7 @@ using a `for-in` loop.
 The following example shows you how to read elements using  a `for-in` loop.
 
 <?code-excerpt "iterables/test/iterables_test.dart (for-in)"?>
-```dart:run-dartpad:ga_id-for_in_loop
+```dartpad
 void main() {
   const iterable = ['Salad', 'Popcorn', 'Toast'];
   for (final element in iterable) {
@@ -173,7 +173,7 @@ results in a [StateError.][StateError class]
 :::
 
 <?code-excerpt "iterables/test/iterables_test.dart (first-last)"?>
-```dart:run-dartpad:ga_id-first_and_last
+```dartpad
 void main() {
   Iterable<String> iterable = const ['Salad', 'Popcorn', 'Toast'];
   print('The first element is ${iterable.first}');
@@ -211,7 +211,7 @@ Run the following example to see how `firstWhere()` works.
 Do you think all the functions will give the same result?
 
 <?code-excerpt "iterables/test/iterables_test.dart (first-where-long)"?>
-```dart:run-dartpad:height-565px:ga_id-using_firstwhere
+```dartpad
 bool predicate(String item) {
   return item.length > 5;
 }
@@ -313,7 +313,7 @@ satisfies the following conditions:
 All the elements in the test data are [strings][String class];
 you can check the class documentation for help.
 
-```dart:run-dartpad:theme-dark:ga_id-practice_writing_a_test_predicate
+```dartpad theme="dark"
 // Implement the predicate of singleWhere
 // with the following conditions
 // * The element contains the character `'a'`
@@ -421,7 +421,7 @@ you can use to verify conditions:
 Run this exercise to see them in action.
 
 <?code-excerpt "iterables/test/iterables_test.dart (any-every)"?>
-```dart:run-dartpad:height-255px:ga_id-using_any_and_every
+```dartpad
 void main() {
   const items = ['Salad', 'Popcorn', 'Toast'];
 
@@ -470,7 +470,7 @@ Use `any()` and `every()` to implement two functions:
 * Part 2: Implement `everyUserOver13()`.
   * Return `true` if all users are 14 or older.
 
-```dart:run-dartpad:theme-dark:height-395px:ga_id-verify_iterable
+```dartpad
 bool anyUserUnder18(Iterable<User> users) {
   // TODO: Implement the anyUserUnder18 function.
 }
@@ -660,7 +660,7 @@ Run this example to see how `where()` can be used together with other
 methods like `any()`.
 
 <?code-excerpt "iterables/test/iterables_test.dart (numbers-where)"?>
-```dart:run-dartpad:height-380px:ga_id-using_where
+```dartpad
 void main() {
   var evenNumbers = const [1, -2, 3, 42].where((number) => number.isEven);
 
@@ -703,7 +703,7 @@ Run this example to see how `takeWhile()` and `skipWhile()` can
 split an `Iterable` containing numbers.
 
 <?code-excerpt "iterables/test/iterables_test.dart (take-while-long)"?>
-```dart:run-dartpad:ga_id-using_takewhile
+```dartpad
 void main() {
   const numbers = [1, 3, -2, 0, 4, 5];
 
@@ -747,7 +747,7 @@ Use `where()` to implement two functions:
   * Return an `Iterable` containing all users with
     names of length 3 or less.
 
-```dart:run-dartpad:theme-dark:height-380px:ga_id-filtering_elements_from_a_list
+```dartpad theme="dark"
 Iterable<User> filterOutUnder21(Iterable<User> users) {
   // TODO: Implement the filterOutUnder21 function.
 }
@@ -893,7 +893,7 @@ multiply all the elements of an `Iterable` by 2.
 What do you think the output will be?
 
 <?code-excerpt "iterables/test/iterables_test.dart (numbers-by-two)"?>
-```dart:run-dartpad:ga_id-using_map
+```dartpad
 void main() {
   var numbersByTwo = const [1, -2, 3, 42].map((number) => number * 2);
   print('Numbers: $numbersByTwo');
@@ -913,7 +913,7 @@ contains strings containing each user's name and age.
 Each string in the `Iterable` must follow this format:
 `'{name} is {age}'`—for example `'Alice is 21'`.
 
-```dart:run-dartpad:theme-dark:height-310px:ga_id-mapping_to_a_different_type
+```dartpad theme="dark"
 Iterable<String> getNameAndAges(Iterable<User> users) {
   // TODO: Implement the getNameAndAges function.
 }
@@ -1043,7 +1043,7 @@ Part 3: Implement `validEmailAddresses()`.
 - Use the provided function `isValidEmailAddress()` to evaluate whether
   an `EmailAddress` is valid.
 
-```dart:run-dartpad:theme-dark:height-600px:ga_id-putting_it_all_together
+```dartpad theme="dark"
 Iterable<EmailAddress> parseEmailAddresses(Iterable<String> strings) {
   // TODO: Implement the parseEmailAddresses function.
 }

src/content/language/callable-objects.md

@@ -25,7 +25,7 @@ that takes three strings and concatenates them, separating each with a space,
 and appending an exclamation. Click **Run** to execute the code.
 
 <?code-excerpt "misc/lib/language_tour/callable_objects.dart"?>
-```dart:run-dartpad:height-350px:ga_id-callable_objects
+```dartpad
 class WannabeFunction {
   String call(String a, String b, String c) => '$a $b $c!';
 }

src/content/language/constructors.md

@@ -430,7 +430,7 @@ The following example initializes three `final` fields in an initializer list.
 To execute the code, click **Run**.
 
 <?code-excerpt "point_with_distance_field.dart"?>
-```dart:run-dartpad:height-340px:ga_id-initializer_list
+```dartpad
 import 'dart:math';
 
 class Point {
@@ -484,7 +484,7 @@ the `Employee` class constructor calls the named constructor
 for its superclass, `Person`. To execute the following code, click **Run**.
 
 <?code-excerpt "employee.dart (super)" plaster="none"?>
-```dart:run-dartpad:height-450px:ga_id-non_default_superclass_constructor
+```dartpad
 class Person {
   String? firstName;
 

src/content/language/functions.md

@@ -309,7 +309,7 @@ for (var item in uppercaseList) {
 Click **Run** to execute the code.
 
 <?code-excerpt "misc/test/language_tour/functions_test.dart (anonymous-function-main)"?>
-```dart:run-dartpad:height-400px:ga_id-anonymous_functions
+```dartpad
 void main() {
   const list = ['apples', 'bananas', 'oranges'];