From 54ed73e5248ed6aea7872f379badec1df9182701 Mon Sep 17 00:00:00 2001
From: mhatvan <markus_hatvan@aon.at>
Date: Sun, 6 Sep 2020 16:39:58 +0200
Subject: [PATCH] feat(a11y): add no-redundant-roles rule (#820)

- flagging easy cases of redundant aria roles on html tags for now

Signed-off-by: mhatvan <markus_hatvan@aon.at>
---
 src/compiler/compile/nodes/Element.ts         | 75 +++++++++++++--
 .../a11y-no-redundant-roles/input.svelte      | 15 +++
 .../a11y-no-redundant-roles/warnings.json     | 92 +++++++++++++++++++
 3 files changed, 175 insertions(+), 7 deletions(-)
 create mode 100644 test/validator/samples/a11y-no-redundant-roles/input.svelte
 create mode 100644 test/validator/samples/a11y-no-redundant-roles/warnings.json

diff --git a/src/compiler/compile/nodes/Element.ts b/src/compiler/compile/nodes/Element.ts
index 6636c6b87b..b7ef3c471e 100644
--- a/src/compiler/compile/nodes/Element.ts
+++ b/src/compiler/compile/nodes/Element.ts
@@ -214,12 +214,12 @@ export default class Element extends Node {
 				}
 
 				case 'Transition':
-				{
-					const transition = new Transition(component, this, scope, node);
-					if (node.intro) this.intro = transition;
-					if (node.outro) this.outro = transition;
-					break;
-				}
+					{
+						const transition = new Transition(component, this, scope, node);
+						if (node.intro) this.intro = transition;
+						if (node.outro) this.outro = transition;
+						break;
+					}
 
 				case 'Animation':
 					this.animation = new Animation(component, this, scope, node);
@@ -357,6 +357,67 @@ export default class Element extends Node {
 						message
 					});
 				}
+
+				const implicitAriaSemantics = new Map([
+					// ['a', ''],
+					// ['area', ''],
+					['article', 'article'],
+					['aside', 'complementary'],
+					['body', 'document'],
+					['button', 'button'],
+					['datalist', 'listbox'],
+					['dd', 'definition'],
+					['dfn', 'term'],
+					['details', 'group'],
+					['dialog', 'dialog'],
+					['dt', 'term'],
+					['fieldset', 'group'],
+					['figure', 'figure'],
+					// ['footer', ''],
+					['form', 'form'],
+					['h1', 'heading'],
+					['h2', 'heading'],
+					['h3', 'heading'],
+					['h4', 'heading'],
+					['h5', 'heading'],
+					['h6', 'heading'],
+					// ['header', ''],
+					['hr', 'separator'],
+					// ['img', ''],
+					// ['input', ''],
+					['li', 'listitem'],
+					['link', 'link'],
+					['main', 'main'],
+					['math', 'math'],
+					['menu', 'list'],
+					['nav', 'navigation'],
+					['ol', 'list'],
+					['optgroup', 'group'],
+					['option', 'option'],
+					['output', 'status'],
+					['progress', 'progressbar'],
+					['section', 'region'],
+					// ['select', ''],
+					['summary', 'button'],
+					['table', 'table'],
+					['tbody', 'rowgroup'],
+					['textarea', 'textbox'],
+					['tfoot', 'rowgroup'],
+					['thead', 'rowgroup'],
+					// ['td', ''],
+					// ['th', ''],
+					['tr', 'row'],
+					['ul', 'list'],
+					['ul', 'list']
+				]);
+
+				const redundantAriaRole = implicitAriaSemantics.get(this.name);
+
+				if (value === redundantAriaRole)
+					component.warn(this, {
+						code: `a11y-no-redundant-roles`,
+						message: `A11y: The element <${this.name}> has an implicit role of '${redundantAriaRole}'. Defining this explicitly is redundant and should be avoided.`
+					});
 			}
 
 			// no-access-key
@@ -519,7 +580,7 @@ export default class Element extends Node {
 		}
 
 		if (this.name === 'label') {
-			const has_input_child = this.children.some(i => (i instanceof Element && a11y_labelable.has(i.name) ));
+			const has_input_child = this.children.some(i => (i instanceof Element && a11y_labelable.has(i.name)));
 			if (!attribute_map.has('for') && !has_input_child) {
 				component.warn(this, {
 					code: `a11y-label-has-associated-control`,
diff --git a/test/validator/samples/a11y-no-redundant-roles/input.svelte b/test/validator/samples/a11y-no-redundant-roles/input.svelte
new file mode 100644
index 0000000000..d5a67cfeeb
--- /dev/null
+++ b/test/validator/samples/a11y-no-redundant-roles/input.svelte
@@ -0,0 +1,15 @@
+<!-- should not warn -->
+<article role="feed" />
+<aside role="region" />
+<button role="radio" />
+<form role="search">foo</form>
+<h1 role="presentation">foo</h1>
+<section role="contentinfo">foo</section>
+
+<!-- should warn -->
+<article role="article" />
+<aside role="complementary" />
+<button role="button" />
+<form role="form">foo</form>
+<h1 role="heading">foo</h1>
+<section role="region">foo</section>
diff --git a/test/validator/samples/a11y-no-redundant-roles/warnings.json b/test/validator/samples/a11y-no-redundant-roles/warnings.json
new file mode 100644
index 0000000000..e0e01a57f7
--- /dev/null
+++ b/test/validator/samples/a11y-no-redundant-roles/warnings.json
@@ -0,0 +1,92 @@
+[
+	{
+		"code": "a11y-no-redundant-roles",
+		"message": "A11y: The element <article> has an implicit role of 'article'. Defining this explicitly is redundant and should be avoided.",
+		"pos": 225,
+		"start": {
+			"line": 10,
+			"column": 0,
+			"character": 225
+		},
+		"end": {
+			"line": 10,
+			"column": 26,
+			"character": 251
+		}
+	},
+	{
+		"code": "a11y-no-redundant-roles",
+		"message": "A11y: The element <aside> has an implicit role of 'complementary'. Defining this explicitly is redundant and should be avoided.",
+		"pos": 252,
+		"start": {
+			"line": 11,
+			"column": 0,
+			"character": 252
+		},
+		"end": {
+			"line": 11,
+			"column": 30,
+			"character": 282
+		}
+	},
+	{
+		"code": "a11y-no-redundant-roles",
+		"message": "A11y: The element <button> has an implicit role of 'button'. Defining this explicitly is redundant and should be avoided.",
+		"pos": 283,
+		"start": {
+			"line": 12,
+			"column": 0,
+			"character": 283
+		},
+		"end": {
+			"line": 12,
+			"column": 24,
+			"character": 307
+		}
+	},
+	{
+		"code": "a11y-no-redundant-roles",
+		"message": "A11y: The element <form> has an implicit role of 'form'. Defining this explicitly is redundant and should be avoided.",
+		"pos": 308,
+		"start": {
+			"line": 13,
+			"column": 0,
+			"character": 308
+		},
+		"end": {
+			"line": 13,
+			"column": 28,
+			"character": 336
+		}
+	},
+	{
+		"code": "a11y-no-redundant-roles",
+		"message": "A11y: The element <h1> has an implicit role of 'heading'. Defining this explicitly is redundant and should be avoided.",
+		"pos": 337,
+		"start": {
+			"line": 14,
+			"column": 0,
+			"character": 337
+		},
+		"end": {
+			"line": 14,
+			"column": 27,
+			"character": 364
+		}
+	},
+	{
+		"code": "a11y-no-redundant-roles",
+		"message": "A11y: The element <section> has an implicit role of 'region'. Defining this explicitly is redundant and should be avoided.",
+		"pos": 365,
+		"start": {
+			"line": 15,
+			"column": 0,
+			"character": 365
+		},
+		"end": {
+			"line": 15,
+			"column": 36,
+			"character": 401
+		}
+	}
+]