feat!: add two more cases to no-implicit-coercion (#17832)

* add two more cases * fix comment * docs * add allow * change operator * change docs * use - - * add tests * don't fix numbers * Check type directly Co-authored-by: Francesco Trotta <github@fasttime.org> * add examples * Refactor implicit coercion check in no-implicit-coercion rule * fix test * fix test * Revert "Refactor implicit coercion check in no-implicit-coercion rule" * make non-fixable * Revert "fix test" * add back test --------- Co-authored-by: Francesco Trotta <github@fasttime.org>
eslint · Dec 27, 2023 · 0b21e1f · 0b21e1f
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diff --git a/docs/src/rules/no-implicit-coercion.md b/docs/src/rules/no-implicit-coercion.md
@@ -14,6 +14,8 @@ Such as:
 var b = !!foo;
 var b = ~foo.indexOf(".");
 var n = +foo;
+var n = -(-foo);
+var n = foo - 0;
 var n = 1 * foo;
 var s = "" + foo;
 foo += ``;
@@ -26,6 +28,8 @@ var b = Boolean(foo);
 var b = foo.indexOf(".") !== -1;
 var n = Number(foo);
 var n = Number(foo);
+var n = Number(foo);
+var n = Number(foo);
 var s = String(foo);
 foo = String(foo);
 ```
@@ -42,7 +46,7 @@ This rule has three main options and one override option to allow some coercions
 * `"number"` (`true` by default) - When this is `true`, this rule warns shorter type conversions for `number` type.
 * `"string"` (`true` by default) - When this is `true`, this rule warns shorter type conversions for `string` type.
 * `"disallowTemplateShorthand"` (`false` by default) - When this is `true`, this rule warns `string` type conversions using `${expression}` form.
-* `"allow"` (`empty` by default) - Each entry in this array can be one of `~`, `!!`, `+` or `*` that are to be allowed.
+* `"allow"` (`empty` by default) - Each entry in this array can be one of `~`, `!!`, `+`, `- -`, `-`, or `*` that are to be allowed.
 
 Note that operator `+` in `allow` list would allow `+foo` (number coercion) as well as `"" + foo` (string coercion).
 
@@ -87,6 +91,8 @@ Examples of **incorrect** code for the default `{ "number": true }` option:
 /*eslint no-implicit-coercion: "error"*/
 
 var n = +foo;
+var n = -(-foo);
+var n = foo - 0;
 var n = 1 * foo;
 ```
 

diff --git a/lib/rules/no-implicit-coercion.js b/lib/rules/no-implicit-coercion.js
@@ -12,7 +12,7 @@ const astUtils = require("./utils/ast-utils");
 //------------------------------------------------------------------------------
 
 const INDEX_OF_PATTERN = /^(?:i|lastI)ndexOf$/u;
-const ALLOWABLE_OPERATORS = ["~", "!!", "+", "*"];
+const ALLOWABLE_OPERATORS = ["~", "!!", "+", "- -", "-", "*"];
 
 /**
  * Parses and normalizes an option object.
@@ -300,6 +300,14 @@ module.exports = {
 
                     report(node, recommendation, true);
                 }
+
+                // -(-foo)
+                operatorAllowed = options.allow.includes("- -");
+                if (!operatorAllowed && options.number && node.operator === "-" && node.argument.type === "UnaryExpression" && node.argument.operator === "-" && !isNumeric(node.argument.argument)) {
+                    const recommendation = `Number(${sourceCode.getText(node.argument.argument)})`;
+
+                    report(node, recommendation, false);
+                }
             },
 
             // Use `:exit` to prevent double reporting
@@ -317,6 +325,14 @@ module.exports = {
                     report(node, recommendation, true);
                 }
 
+                // foo - 0
+                operatorAllowed = options.allow.includes("-");
+                if (!operatorAllowed && options.number && node.operator === "-" && node.right.type === "Literal" && node.right.value === 0 && !isNumeric(node.left)) {
+                    const recommendation = `Number(${sourceCode.getText(node.left)})`;
+
+                    report(node, recommendation, true);
+                }
+
                 // "" + foo
                 operatorAllowed = options.allow.includes("+");
                 if (!operatorAllowed && options.string && isConcatWithEmptyString(node)) {

diff --git a/tests/lib/rules/no-implicit-coercion.js b/tests/lib/rules/no-implicit-coercion.js
@@ -31,18 +31,23 @@ ruleTester.run("no-implicit-coercion", rule, {
         "-foo",
         "+1234",
         "-1234",
+        "- -1234",
         "+Number(lol)",
         "-parseFloat(lol)",
         "2 * foo",
         "1 * 1234",
+        "123 - 0",
         "1 * Number(foo)",
         "1 * parseInt(foo)",
         "1 * parseFloat(foo)",
         "Number(foo) * 1",
+        "Number(foo) - 0",
         "parseInt(foo) * 1",
         "parseFloat(foo) * 1",
+        "- -Number(foo)",
         "1 * 1234 * 678 * Number(foo)",
         "1 * 1234 * 678 * parseInt(foo)",
+        "(1 - 0) * parseInt(foo)",
         "1234 * 1 * 678 * Number(foo)",
         "1234 * 1 * Number(foo) * Number(bar)",
         "1234 * 1 * Number(foo) * parseInt(bar)",
@@ -54,6 +59,7 @@ ruleTester.run("no-implicit-coercion", rule, {
         "1234 * parseInt(foo) * 1 * Number(bar)",
         "1234 * parseFloat(foo) * 1 * parseInt(bar)",
         "1234 * parseFloat(foo) * 1 * Number(bar)",
+        "(- -1234) * (parseFloat(foo) - 0) * (Number(bar) - 0)",
         "1234*foo*1",
         "1234*1*foo",
         "1234*bar*1*foo",
@@ -69,13 +75,17 @@ ruleTester.run("no-implicit-coercion", rule, {
         { code: "!!foo", options: [{ boolean: false }] },
         { code: "~foo.indexOf(1)", options: [{ boolean: false }] },
         { code: "+foo", options: [{ number: false }] },
+        { code: "-(-foo)", options: [{ number: false }] },
+        { code: "foo - 0", options: [{ number: false }] },
         { code: "1*foo", options: [{ number: false }] },
         { code: "\"\"+foo", options: [{ string: false }] },
         { code: "foo += \"\"", options: [{ string: false }] },
         { code: "var a = !!foo", options: [{ boolean: true, allow: ["!!"] }] },
         { code: "var a = ~foo.indexOf(1)", options: [{ boolean: true, allow: ["~"] }] },
         { code: "var a = ~foo", options: [{ boolean: true }] },
         { code: "var a = 1 * foo", options: [{ boolean: true, allow: ["*"] }] },
+        { code: "- -foo", options: [{ number: true, allow: ["- -"] }] },
+        { code: "foo - 0", options: [{ number: true, allow: ["-"] }] },
         { code: "var a = +foo", options: [{ boolean: true, allow: ["+"] }] },
         { code: "var a = \"\" + foo", options: [{ boolean: true, string: true, allow: ["+"] }] },
 
@@ -157,6 +167,15 @@ ruleTester.run("no-implicit-coercion", rule, {
                 type: "UnaryExpression"
             }]
         },
+        {
+            code: "-(-foo)",
+            output: null,
+            errors: [{
+                messageId: "useRecommendation",
+                data: { recommendation: "Number(foo)" },
+                type: "UnaryExpression"
+            }]
+        },
         {
             code: "+foo.bar",
             output: "Number(foo.bar)",
@@ -193,6 +212,15 @@ ruleTester.run("no-implicit-coercion", rule, {
                 type: "BinaryExpression"
             }]
         },
+        {
+            code: "foo.bar-0",
+            output: "Number(foo.bar)",
+            errors: [{
+                messageId: "useRecommendation",
+                data: { recommendation: "Number(foo.bar)" },
+                type: "BinaryExpression"
+            }]
+        },
         {
             code: "\"\"+foo",
             output: "String(foo)",