Priority fixes for 'Breaking up language tour' (#4643)

Sorry that I didn't catch these earlier, I didn't have a chance to
review the changes yet. I've reverted the deployment to a previous
commit until these fixes land, so that google search and other external
links don't lead to broken pages and slightly broken content doesn't
cause confusion.

I have more fixes to follow, but these are the most important to get in.

- Fixes broken merge in extension methods file and other changes
- Adds necessary DartPad inject script to pages that use it
- Implement that when in a "/language" page, "Docs" in the top
menu/navbar shows up as highlighted/active
- Adds redirects for content that moves
- Adjusts existing redirects to point to the new location rather than
old language-tour page
- Updates the "Callable classes" description to match others and have a
period
- Adds the "Language evolution" page back to the sidenav since it
shouldn't be removed completely
- Removes DartPad inject script from language tour which no longer uses
it

Author: parlough

CONTRIBUTING.md

@@ -59,8 +59,8 @@ you'll probably need to change the code in two places:
 1. In a `.md` file for the page.
 2. In a `.dart` file under the `/examples` directory.
 
-For example, say  you want to change the following code in the
-[language tour](https://dart.dev//language/variables):
+For example, say you want to change the following code in the
+[Variables documentation](https://dart.dev/language/variables):
 
 ```
 <?code-excerpt "misc/lib/language_tour/variables.dart (var-decl)"?>
@@ -87,4 +87,4 @@ Just update the PR, and GitHub Actions will run again.
 ## A word about conduct
 
 We pledge to maintain an open and welcoming environment.
-For details, see our [code of conduct](https://dart.dev/code-of-conduct).
+For details, see our [code of conduct](https://dart.dev/community/code-of-conduct).

firebase.json

@@ -169,9 +169,12 @@
       { "source": "/googleapis", "destination": "https://github.com/dart-lang/googleapis", "type": 301 },
       { "source": "/guides/get-started", "destination": "/overview", "type": 301 },
       { "source": "/guides/language/common-prob", "destination": "/guides/language/sound-problems", "type": 301 },
+      { "source": "/guides/language/concurrency", "destination": "/language/concurrency", "type": 301 },
+      { "source": "/guides/language/extension-methods", "destination": "/language/extension-methods", "type": 301 },
       { "source": "/guides/language/library-tour", "destination": "/guides/libraries/library-tour", "type": 301 },
-      { "source": "/guides/language/sound-dart", "destination": "/guides/language/type-system", "type": 301 },
-      { "source": "/guides/language/sound-faq", "destination": "/guides/language/type-system", "type": 301 },
+      { "source": "/guides/language/sound-dart", "destination": "/language/type-system", "type": 301 },
+      { "source": "/guides/language/sound-faq", "destination": "/language/type-system", "type": 301 },
+      { "source": "/guides/language/type-system", "destination": "/language/type-system", "type": 301 },
       { "source": "/guides/platforms", "destination": "/overview#platform", "type": 301 },
       { "source": "/hackathons{,/**}", "destination": "/", "type": 301 },
       { "source": "/hangouts{,/**}", "destination": "/", "type": 301 },

src/_data/side-nav.yml

@@ -92,20 +92,12 @@
           match-page-url-exactly: true
           permalink: /null-safety
         - title: Migrating to null safety
-          urlExactMatch: true
-          match-page-url-exactly: true
           permalink: /null-safety/migration-guide
         - title: Understanding null safety
-          urlExactMatch: true
-          match-page-url-exactly: true
           permalink: /null-safety/understanding-null-safety
         - title: Unsound null safety
-          urlExactMatch: true
-          match-page-url-exactly: true
           permalink: /null-safety/unsound-null-safety
         - title: FAQ
-          urlExactMatch: true
-          match-page-url-exactly: true
           permalink: /null-safety/faq
 
 - title: Effective Dart
@@ -332,6 +324,8 @@
   children:
     - title: FAQ
       permalink: /faq
+    - title: Language evolution
+      permalink: /guides/language/evolution
     - title: Language specification
       permalink: /guides/language/spec    
     - title: Coming from ...

src/_guides/language/language-tour.md

@@ -2,7 +2,6 @@
 title: A tour of the Dart language
 description: A tour of all the major Dart language features.
 short-title: Language tour
-js: [{url: 'https://dartpad.dev/inject_embed.dart.js', defer: true}]
 sitemap: false
 ---
 

src/_includes/navigation-main.html

@@ -15,7 +15,7 @@
     </li>
     <li class="mainnav__get-started">
       <a href="/guides" class="nav-link
-        {% if page_url_path contains '/*/guides/' or page_url_path contains '/*/dart-2/' or page_url_path contains '/*/codelabs/' or page_url_path contains '/*/samples/' or page_url_path contains '/*/tools/' or page_url_path contains '/*/tutorials/' or page_url_path contains '/*/server/' or page_url_path contains '/*/web/' %} active {%- endif -%}">
+        {% if page_url_path contains '/*/guides/' or page_url_path contains '/*/language/' or page_url_path contains '/*/dart-2/' or page_url_path contains '/*/codelabs/' or page_url_path contains '/*/samples/' or page_url_path contains '/*/tools/' or page_url_path contains '/*/tutorials/' or page_url_path contains '/*/server/' or page_url_path contains '/*/web/' %} active {%- endif -%}">
         <span>Docs</span>
       </a>
     </li>

src/_includes/navigation-side.html

@@ -24,7 +24,7 @@
       </li>
       <li class="nav-item">
         <a href="/guides" class="nav-link
-          {%- if page_url_path contains '/*/guides/' or page_url_path contains '/*/dart-2/' or page_url_path contains '/*/codelabs/' or page_url_path contains '/*/samples/' or page_url_path contains '/*/tools/' or page_url_path contains '/*/tutorials/' or page_url_path contains '/*/server/' or page_url_path contains '/*/web/' %} active {%- endif -%}">Docs</a>
+          {%- if page_url_path contains '/*/guides/' or page_url_path contains '/*/language/' or page_url_path contains '/*/dart-2/' or page_url_path contains '/*/codelabs/' or page_url_path contains '/*/samples/' or page_url_path contains '/*/tools/' or page_url_path contains '/*/tutorials/' or page_url_path contains '/*/server/' or page_url_path contains '/*/web/' %} active {%- endif -%}">Docs</a>
       </li>
     </ul>
 

src/language/callable-classes.md

@@ -1,6 +1,7 @@
 ---
 title: Callable classes
-description: How to use the call() method 
+description: Learn how to create and use callable classes in Dart.
+js: [{url: 'https://dartpad.dev/inject_embed.dart.js', defer: true}]
 ---
 
 To allow an instance of your Dart class to be called like a function,

src/language/constructors.md

@@ -1,6 +1,7 @@
 ---
 title: Constructors
 description: Everything about using constructors in Dart.
+js: [{url: 'https://dartpad.dev/inject_embed.dart.js', defer: true}]
 ---
 
 <?code-excerpt replace="/ *\/\/\s+ignore_for_file:[^\n]+\n//g; /(^|\n) *\/\/\s+ignore:[^\n]+\n/$1/g; /(\n[^\n]+) *\/\/\s+ignore:[^\n]+\n/$1\n/g; / *\/\/\s+ignore:[^\n]+//g; /([A-Z]\w*)\d\b/$1/g"?>

src/language/extension-methods.md

@@ -8,15 +8,14 @@ You might use extension methods without even knowing it.
 For example, when you use code completion in an IDE,
 it suggests extension methods alongside regular methods.
 
-Here's an example of using an extension method on `String`
-named `parseInt()` that's defined in `string_apis.dart`:
-
-```dart
-import 'string_apis.dart';
-...
-print('42'.padLeft(5)); // Use a String method.
-print('42'.parseInt()); // Use an extension method.
-```
+<iframe width="560" height="315"
+src="https://www.youtube.com/embed/D3j0OSfT9ZI"
+frameborder="0"
+allow="accelerometer; encrypted-media; gyroscope; picture-in-picture"
+allowfullscreen>
+</iframe>
+_If you like to learn by watching videos,
+here's a good overview of extension methods._
 
 ## Overview
 
@@ -272,20 +271,6 @@ For more information about extension methods, see the following:
 * [Feature specification][specification]
 * [Extension methods sample][sample]
 
-<<<<<<< HEAD:src/_guides/language/extension-methods.md
-=======
-<iframe width="560" height="315"
-  src="https://www.youtube.com/embed/D3j0OSfT9ZI"
-  frameborder="0"
-  allow="accelerometer; encrypted-media; gyroscope; picture-in-picture"
-  allowfullscreen>
-</iframe>
-<em>If you like to learn by watching videos,
-here's a good overview of extension methods.</em>
-
->>>>>>> 59e53837 (breakup language-tour to new pages, fix on-page links):src/language/extension-methods.md
 [specification]: https://github.com/dart-lang/language/blob/master/accepted/2.7/static-extension-methods/feature-specification.md#dart-static-extension-methods-design
-
 [article]: https://medium.com/dartlang/extension-methods-2d466cd8b308
-
 [sample]: https://github.com/dart-lang/samples/tree/master/extension_methods

src/language/functions.md

@@ -1,6 +1,7 @@
 ---
 title: Functions
 description: Everything about functions in Dart.
+js: [{url: 'https://dartpad.dev/inject_embed.dart.js', defer: true}]
 ---
 
 Dart is a true object-oriented language, so even functions are objects