Assertion methods auto correction for use-t-well rule

docs/rules/use-t-well.md

@@ -4,7 +4,7 @@ Translations: [Français](https://github.com/avajs/ava-docs/blob/master/fr_FR/re
 
 Prevent the use of unknown assertion methods and the access to members other than the assertion methods and `.context`, as well as some known misuses of `t`.
 
-This rule is partly fixable. It will replace misspelled `.falsey` with `.falsy`.
+This rule is partly fixable. It can fix most misspelled assertion method names and incorrect usages of `.skip`.
 
 
 ## Fail
@@ -14,12 +14,13 @@ const test = require('ava');
 
 test('main', t => {
 	t(value); // `t` is not a function
-	t.depEqual(value, [2]); // Unknown assertion method `.depEqual`
-	t.contxt.foo = 100; // Unknown member `.contxt`. Use `.context.contxt` instead
+	t.depEqual(value, [2]); // Misspelled `.deepEqual` as `.depEqual`, fixable
+	t.contxt.foo = 100; // Misspelled `.context` as `.contxt`, fixable
+	t.deepEqual.skip.skip(); // Too many chained uses of `.skip`, fixable
+	t.skip.deepEqual(1, 1); // `.skip` modifier should be the last in chain, fixable
 	t.foo = 1000; // Unknown member `.foo`. Use `.context.foo` instead
 	t.deepEqual.is(value, value); // Can't chain assertion methods
 	t.skip(); // Missing assertion method
-	t.deepEqual.skip.skip(); // Too many chained uses of `.skip`
 });
 ```
 

rules/use-t-well.js

@@ -3,35 +3,91 @@ const {visitIf} = require('enhance-visitors');
 const util = require('../util');
 const createAvaRule = require('../create-ava-rule');
 
-const isMethod = name => util.executionMethods.has(name);
+class MicroCorrecter {
+	constructor(words) {
+		this.words = new Set(words);
+
+		const letters = new Set();
+		words.forEach(word => word.split('').forEach(letter => letters.add(letter)));
+		this.letters = [...letters];
+	}
+
+	edits(word) {
+		const edits = [];
+		const {length} = word;
+		const {letters} = this;
+
+		for (let i = 0; i < length; i++) {
+			edits.push(word.slice(0, i) + word.slice(i + 1)); // Skip
+			for (const letter of letters) {
+				edits.push(word.slice(0, i) + letter + word.slice(i + 1)); // Replace
+			}
+		}
+
+		for (let i = 1; i < length; i++) {
+			edits.push(word.slice(0, i - 1) + word[i] + word[i - 1] + word.slice(i + 1)); // Transposition
+		}
+
+		for (let i = 0; i <= length; i++) {
+			for (const letter of letters) {
+				edits.push(word.slice(0, i) + letter + word.slice(i)); // Addition
+			}
+		}
+
+		return edits;
+	}
+
+	correct(word, distance) {
+		const {words} = this;
+
+		if (words.has(word)) {
+			return word;
+		}
+
+		if (distance > 0) {
+			const edits = this.edits(word);
+
+			for (const edit of edits) {
+				if (words.has(edit)) {
+					return edit;
+				}
+			}
+
+			if (distance > 1) {
+				for (const edit of edits) {
+					const correction = this.correct(edit, distance - 1);
+					if (correction !== undefined) {
+						return correction;
+					}
+				}
+			}
+		}
+	}
+}
+
+const properties = new Set([
+	...util.executionMethods,
+	'context',
+	'title',
+	'skip'
+]);
+
+const correcter = new MicroCorrecter([...properties]);
 
 const isCallExpression = node =>
 	node.parent.type === 'CallExpression' &&
 	node.parent.callee === node;
 
-const getMemberStats = members => {
-	const initial = {
-		skip: [],
-		falsey: [],
-		method: [],
-		other: []
-	};
-
-	return members.reduce((res, member) => {
-		if (member === 'skip') {
-			res.skip.push(member);
-		} else if (member === 'falsey') {
-			res.falsey.push(member);
-		} else if (isMethod(member)) {
-			res.method.push(member);
-		} else {
-			res.other.push(member);
-		}
+const getMemberNodes = node => {
+	if (node.object.type === 'MemberExpression') {
+		return getMemberNodes(node.object).concat(node.property);
+	}
 
-		return res;
-	}, initial);
+	return [node.property];
 };
 
+const correctIdentifier = name => correcter.correct(name, Math.max(0, Math.min(name.length - 2, 2)));
+
 const create = context => {
 	const ava = createAvaRule();
 
@@ -57,67 +113,94 @@ const create = context => {
 				return;
 			}
 
-			const members = util.getMembers(node);
-			const stats = getMemberStats(members);
-
-			if (members[0] === 'context') {
-				// Anything is fine when of the form `t.context...`
-				if (members.length === 1 && isCallExpression(node)) {
-					// Except `t.context()`
-					context.report({
-						node,
-						message: 'Unknown assertion method `.context`.'
-					});
+			const members = getMemberNodes(node);
+
+			const skipPositions = [];
+			let hadCall = false;
+			for (const [i, member] of members.entries()) {
+				const {name} = member;
+
+				let corrected = correctIdentifier(name);
+
+				if (i !== 0 && (corrected === 'context' || corrected === 'title')) { // `context` and `title` can only be first
+					corrected = undefined;
 				}
 
-				return;
-			}
+				if (corrected !== name) {
+					if (corrected === undefined) {
+						if (isCallExpression(node)) {
+							context.report({
+								node,
+								message: `Unknown assertion method \`.${name}\`.`
+							});
+						} else {
+							context.report({
+								node,
+								message: `Unknown member \`.${name}\`. Use \`.context.${name}\` instead.`
+							});
+						}
+					} else {
+						context.report({
+							node,
+							message: `Misspelled \`.${corrected}\` as \`.${name}\`.`,
+							fix: fixer => fixer.replaceText(member, corrected)
+						});
+					}
 
-			if (members[0] === 'title') {
-				// Anything is fine when of the form `t.title...`
-				if (members.length === 1 && isCallExpression(node)) {
-					// Except `t.title()`
-					context.report({
-						node,
-						message: 'Unknown assertion method `.title`.'
-					});
+					return; // Don't check further
 				}
 
-				return;
-			}
+				if (name === 'context' || name === 'title') {
+					if (members.length === 1 && isCallExpression(node)) {
+						context.report({
+							node,
+							message: `Unknown assertion method \`.${name}\`.`
+						});
+					}
+
+					return; // Don't check further
+				}
 
-			if (isCallExpression(node)) {
-				if (stats.other.length > 0) {
-					context.report({
-						node,
-						message: `Unknown assertion method \`.${stats.other[0]}\`.`
-					});
-				} else if (stats.skip.length > 1) {
-					context.report({
-						node,
-						message: 'Too many chained uses of `.skip`.'
-					});
-				} else if (stats.falsey.length > 0) {
-					context.report({
-						node,
-						message: 'Misspelled `.falsy` as `.falsey`.',
-						fix: fixer => fixer.replaceText(node.property, 'falsy')
-					});
-				} else if (stats.method.length > 1) {
-					context.report({
-						node,
-						message: 'Can\'t chain assertion methods.'
-					});
-				} else if (stats.method.length === 0) {
-					context.report({
-						node,
-						message: 'Missing assertion method.'
-					});
+				if (name === 'skip') {
+					skipPositions.push(i);
+				} else {
+					if (hadCall) {
+						context.report({
+							node,
+							message: 'Can\'t chain assertion methods.'
+						});
+					}
+
+					hadCall = true;
 				}
-			} else if (stats.other.length > 0) {
+			}
+
+			if (!hadCall) {
+				context.report({
+					node,
+					message: 'Missing assertion method.'
+				});
+			}
+
+			if (skipPositions.length > 1) {
+				context.report({
+					node,
+					message: 'Too many chained uses of `.skip`.',
+					fix: fixer => {
+						const chain = ['t', ...members.map(member => member.name).filter(name => name !== 'skip'), 'skip'];
+						return fixer.replaceText(node, chain.join('.'));
+					}
+				});
+			}
+
+			if (skipPositions.length === 1 && skipPositions[0] !== members.length - 1) {
 				context.report({
 					node,
-					message: `Unknown member \`.${stats.other[0]}\`. Use \`.context.${stats.other[0]}\` instead.`
+					message: '`.skip` modifier should be the last in chain.',
+					fix: fixer => {
+						const chain = ['t', ...members.map(member => member.name).filter(name => name !== 'skip'), 'skip'];
+						return fixer.replaceText(node, chain.join('.'));
+					}
 				});
 			}
 		})