Fix: fix no-unused-vars (fixes #44) (#45)

* Fix: fix no-unused-vars (fixes #44) * add more cases * support array destructuring * add more cases
aladdin-add · Jun 9, 2019 · eb118f1 · eb118f1
1 parent b716803
commit eb118f1
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Showing 3 changed files with 77 additions and 14 deletions.
diff --git a/lib/ast-utils.js b/lib/ast-utils.js
@@ -6,6 +6,7 @@
 "use strict";
 
 const anyFunctionPattern = /^(?:Function(?:Declaration|Expression)|ArrowFunctionExpression)$/u;
+const sideEffectFree = new Set(["Literal", "Identifier", "ThisExpression"]);
 
 /**
  * Finds a function node from ancestors of a node.
@@ -28,7 +29,7 @@ function getUpperFunction(node) {
  * @returns {boolean} result
  */
 function hasSideEffect(node) {
-    if (["Literal", "Identifier", "ThisExpression"].includes(node.type)) {
+    if (sideEffectFree.has(node.type)) {
         return false;
     }
 
@@ -40,10 +41,6 @@ function hasSideEffect(node) {
         return node.expressions.length !== 0;
     }
 
-    if (node.type === "AssignmentExpression") {
-        return hasSideEffect(node.right);
-    }
-
     return true;
 }
 

diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
@@ -10,6 +10,8 @@ const { hasSideEffect } = require("../ast-utils");
 
 const rule = utils.getFixableRule("no-unused-vars", false);
 
+const commaFilter = { filter: token => token.value === "," };
+
 module.exports = ruleComposer.mapReports(
     rule,
     (problem, { sourceCode }) => {
@@ -35,20 +37,20 @@ module.exports = ruleComposer.mapReports(
                     }
 
                     if (parent !== grand.specifiers[grand.specifiers.length - 1]) {
-                        const comma = sourceCode.getTokenAfter(parent, { filter: token => token.value === "," });
+                        const comma = sourceCode.getTokenAfter(parent, commaFilter);
 
                         return [fixer.remove(parent), fixer.remove(comma)];
                     }
 
                     if (grand.specifiers.filter(specifier => specifier.type === "ImportSpecifier").length === 1) {
-                        const start = sourceCode.getTokenBefore(parent, { filter: token => token.value === "," }),
+                        const start = sourceCode.getTokenBefore(parent, commaFilter),
                             end = sourceCode.getTokenAfter(parent, { filter: token => token.value === "}" });
 
                         return fixer.removeRange([start.range[0], end.range[1]]);
                     }
 
                     return fixer.removeRange([
-                        sourceCode.getTokenBefore(parent, { filter: token => token.value === "," }).range[0],
+                        sourceCode.getTokenBefore(parent, commaFilter).range[0],
                         parent.range[1]
                     ]);
                 case "VariableDeclarator":
@@ -65,13 +67,13 @@ module.exports = ruleComposer.mapReports(
                     }
 
                     if (parent !== grand.declarations[grand.declarations.length - 1]) {
-                        const comma = sourceCode.getTokenAfter(parent, { filter: token => token.value === "," });
+                        const comma = sourceCode.getTokenAfter(parent, commaFilter);
 
                         return [fixer.remove(parent), fixer.remove(comma)];
                     }
 
                     return [
-                        fixer.remove(sourceCode.getTokenBefore(parent, { filter: token => token.value === "," })),
+                        fixer.remove(sourceCode.getTokenBefore(parent, commaFilter)),
                         fixer.remove(parent)
                     ];
                 case "AssignmentPattern":
@@ -81,7 +83,29 @@ module.exports = ruleComposer.mapReports(
                     return fixer.remove(parent);
                 case "RestElement":
                 case "Property":
-                    return fixer.remove(parent);
+                    if (!grand) {
+                        return null;
+                    }
+
+                    if (grand.properties.length === 1) {
+                        const identifierRemoval = fixer.remove(parent);
+                        const comma = sourceCode.getLastToken(grand, commaFilter);
+
+                        return comma ? [identifierRemoval, fixer.remove(comma)] : identifierRemoval;
+                    }
+
+                    if (parent === grand.properties[grand.properties.length - 1]) {
+                        const comma = sourceCode.getTokenBefore(parent, commaFilter);
+
+                        return [fixer.remove(parent), fixer.remove(comma)];
+                    }
+
+                    return [
+                        fixer.remove(parent),
+                        fixer.remove(sourceCode.getTokenAfter(parent, commaFilter))
+                    ];
+                case "ArrayPattern":
+                    return fixer.remove(node);
                 default:
                     return null;
             }

diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
@@ -122,7 +122,12 @@ ruleTester.run("no-unused-vars", rule, {
         },
         {
             code: "var a = b = c",
-            output: "",
+            output: null,
+            errors: [{ type: "Identifier" }]
+        },
+        {
+            code: "var a = b = c()",
+            output: null,
             errors: [{ type: "Identifier" }]
         },
         {
@@ -142,8 +147,27 @@ ruleTester.run("no-unused-vars", rule, {
             errors: [{ type: "Identifier" }]
         },
         {
-            code: "var a = b = c()",
-            output: null,
+            code: "var [a] = c",
+            output: "var [] = c",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ type: "Identifier" }]
+        },
+        {
+            code: "var [a, b] = c",
+            output: "var [, ] = c",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ type: "Identifier" }, { type: "Identifier" }]
+        },
+        {
+            code: "var [a, b] = c; a;",
+            output: "var [a, ] = c; a;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ type: "Identifier" }]
+        },
+        {
+            code: "var [a, b] = c; b;",
+            output: "var [, b] = c; b;",
+            parserOptions: { ecmaVersion: 6 },
             errors: [{ type: "Identifier" }]
         },
         {
@@ -168,6 +192,12 @@ ruleTester.run("no-unused-vars", rule, {
             parserOptions: { ecmaVersion: 6 },
             errors: [{ type: "Identifier" }]
         },
+        {
+            code: "let {a,} = b",
+            output: "let {} = b",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ type: "Identifier" }]
+        },
         {
             code: "let {a1: a2} = b",
             output: "let {} = b",
@@ -185,6 +215,18 @@ ruleTester.run("no-unused-vars", rule, {
             output: null,
             parserOptions: { ecmaVersion: 6 },
             errors: [{ type: "Identifier" }]
+        },
+        {
+            code: "let {a, b} = c; b;",
+            output: "let { b} = c; b;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ type: "Identifier" }]
+        },
+        {
+            code: "let {a, b} = c; a;",
+            output: "let {a } = c; a;",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ type: "Identifier" }]
         }
     ]
 });