Add suggestion for 'non-existent-operator' (#336)

README.md

@@ -17,7 +17,7 @@ Rules in this category aim to find places in code which have a high chance of be
 * Return values from functions without side effects should not be ignored ([`no-ignored-return`]) (*uses-types*)
 * Loops with at most one iteration should be refactored ([`no-one-iteration-loop`])
 * The output of functions that don't return anything should not be used ([`no-use-of-empty-return-value`])
-* Non-existent operators '=+', '=-' and '=!' should not be used ([`non-existent-operator`])
+* Non-existent operators '=+', '=-' and '=!' should not be used ([`non-existent-operator`]) (:wrench: *fixable*)
 
 ### Code Smell Detection :pig:
 

docs/rules/non-existent-operator.md

@@ -1,5 +1,7 @@
 # non-existent-operator
 
+:wrench: *fixable*
+
 The use of operators pairs (`=+`, `=-` or `=!`) where the reversed, single operator was meant (`+=`, `-=` or `!=`) will compile and run, but not produce the expected results.
 
 This rule raises an issue when `=+`, `=-` and `=!` are used without any space between the two operators and when there is at least one whitespace after.

src/rules/non-existent-operator.ts

@@ -26,9 +26,11 @@ const rule: TSESLint.RuleModule<string, string[]> = {
   meta: {
     messages: {
       useExistingOperator: 'Was "{{operator}}=" meant instead?',
+      suggestExistingOperator: 'Replace with "{{operator}}" operator',
     },
     schema: [],
     type: 'problem',
+    hasSuggestions: true,
     docs: {
       description: 'Non-existent operators "=+", "=-" and "=!" should not be used',
       recommended: 'error',
@@ -75,12 +77,28 @@ function checkOperator(
       areAdjacent(assignmentOperatorToken, unaryOperatorToken) &&
       !areAdjacent(unaryOperatorToken, expressionFirstToken)
     ) {
+      const suggest: TSESLint.ReportSuggestionArray<string> = [];
+      if (unaryNode.parent?.type === 'AssignmentExpression') {
+        const range: [number, number] = [
+          assignmentOperatorToken.range[0],
+          unaryOperatorToken.range[1],
+        ];
+        const invertedOperators = unaryOperatorToken.value + assignmentOperatorToken.value;
+        suggest.push({
+          messageId: 'suggestExistingOperator',
+          data: {
+            operator: invertedOperators,
+          },
+          fix: fixer => fixer.replaceTextRange(range, invertedOperators),
+        });
+      }
       context.report({
         messageId: 'useExistingOperator',
         data: {
           operator: unaryNode.operator,
         },
         loc: { start: assignmentOperatorToken.loc.start, end: unaryOperatorToken.loc.end },
+        suggest,
       });
     }
   }

tests/rules/non-existent-operator.test.ts

@@ -53,6 +53,15 @@ ruleTester.run("Non-existent operators '=+', '=-' and '=!' should not be used",
           endLine: 1,
           column: 3,
           endColumn: 5,
+          suggestions: [
+            {
+              messageId: 'suggestExistingOperator',
+              data: {
+                operator: '+=',
+              },
+              output: `x += y;`,
+            },
+          ],
         },
       ],
     },
@@ -114,6 +123,7 @@ ruleTester.run("Non-existent operators '=+', '=-' and '=!' should not be used",
           endLine: 1,
           column: 7,
           endColumn: 9,
+          suggestions: [],
         },
       ],
     },