Add suggestion for 'no-collection-size-mischeck' (#340)

README.md

@@ -27,7 +27,7 @@ Code Smells, or maintainability issues, are raised for places of code which migh
 * "if ... else if" constructs should end with "else" clauses ([`elseif-without-else`]) (*disabled*)
 * "switch" statements should not have too many "case" clauses ([`max-switch-cases`])
 * Collapsible "if" statements should be merged ([`no-collapsible-if`])
-* Collection sizes and array length comparisons should make sense ([`no-collection-size-mischeck`]) (*uses-types*)
+* Collection sizes and array length comparisons should make sense ([`no-collection-size-mischeck`]) (:wrench: *fixable*, *uses-types*)
 * String literals should not be duplicated ([`no-duplicate-string`])
 * Two branches in a conditional structure should not have exactly the same implementation ([`no-duplicated-branches`])
 * Boolean expressions should not be gratuitous ([`no-gratuitous-expressions`])

docs/rules/no-collection-size-mischeck.md

@@ -1,5 +1,7 @@
 # no-collection-size-mischeck
 
+:wrench: *fixable*
+
 The size of a collection and the length of an array are always greater than or equal to zero. So testing that a size or length is greater than or equal to zero doesn't make sense, since the result is always `true`. Similarly testing that it is less than zero will always return `false`. Perhaps the intent was to check the non-emptiness of the collection or array instead.
 
 ## Noncompliant Code Example

src/rules/no-collection-size-mischeck.ts

@@ -31,9 +31,11 @@ const rule: TSESLint.RuleModule<string, string[]> = {
     messages: {
       fixCollectionSizeCheck:
         'Fix this expression; {{propertyName}} of "{{objectName}}" is always greater or equal to zero.',
+      suggestFixedSizeCheck: 'Use "{{operator}}" for {{operation}} check',
     },
     schema: [],
     type: 'problem',
+    hasSuggestions: true,
     docs: {
       description: 'Collection sizes and array length comparisons should make sense',
       recommended: 'error',
@@ -63,6 +65,7 @@ const rule: TSESLint.RuleModule<string, string[]> = {
                   objectName: context.getSourceCode().getText(object),
                 },
                 node,
+                suggest: getSuggestion(expr, property.name, context),
               });
             }
           }
@@ -82,4 +85,26 @@ function isCollection(node: TSESTree.Node, services: RequiredParserServices) {
   return !!tp.symbol && CollectionLike.includes(tp.symbol.name);
 }
 
+function getSuggestion(
+  expr: TSESTree.BinaryExpression,
+  operation: string,
+  context: TSESLint.RuleContext<string, string[]>,
+): TSESLint.ReportSuggestionArray<string> {
+  const { left, operator } = expr;
+  const operatorToken = context
+    .getSourceCode()
+    .getTokenAfter(left, token => token.value === operator)!;
+  const fixedOperator = operator === '<' ? '==' : '>';
+  return [
+    {
+      messageId: 'suggestFixedSizeCheck',
+      data: {
+        operation,
+        operator: fixedOperator,
+      },
+      fix: fixer => fixer.replaceText(operatorToken, fixedOperator),
+    },
+  ];
+}
+
 export = rule;

tests/rules/no-collection-size-mischeck.test.ts

@@ -54,6 +54,16 @@ ruleTester.run('Collection sizes and array length comparisons should make sense'
           endLine: 1,
           column: 5,
           endColumn: 24,
+          suggestions: [
+            {
+              messageId: 'suggestFixedSizeCheck',
+              data: {
+                operation: 'size',
+                operator: '==',
+              },
+              output: `if (collection.size == 0) {}`,
+            },
+          ],
         },
       ],
     },
@@ -86,6 +96,16 @@ ruleTester.run('Collection sizes and array length comparisons should make sense'
           endLine: 1,
           column: 5,
           endColumn: 27,
+          suggestions: [
+            {
+              messageId: 'suggestFixedSizeCheck',
+              data: {
+                operation: 'length',
+                operator: '>',
+              },
+              output: `if (collection.length > 0) {}`,
+            },
+          ],
         },
       ],
     },