Added no-dynamic-delete rule (palantir#3573)

src/configs/all.ts

@@ -106,6 +106,7 @@ export const rules = {
         true,
         "check-parameters",
     ],
+    "no-dynamic-delete": true,
     "no-empty": true,
     "no-eval": true,
     "no-floating-promises": true,

src/configuration.ts

@@ -242,6 +242,7 @@ export function loadConfigurationFromPath(configFilePath?: string, originalFileP
             }
         } else {
             rawConfigFile = require(resolvedConfigFilePath) as RawConfigFile;
+            // tslint:disable-next-line:no-dynamic-delete
             delete (require.cache as { [key: string]: any })[resolvedConfigFilePath];
         }
 

src/rules/noDynamicDeleteRule.ts

@@ -0,0 +1,102 @@
+/**
+ * @license
+ * Copyright 2013 Palantir Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as tsutils from "tsutils";
+import * as ts from "typescript";
+
+import * as Lint from "../index";
+
+export class Rule extends Lint.Rules.AbstractRule {
+    public static metadata: Lint.IRuleMetadata = {
+        description: "Bans usage of the delete operator with computed key expressions.",
+        optionExamples: [true],
+        options: null,
+        optionsDescription: "Not configurable.",
+        rationale: "Deleting dynamically computed keys is dangerous and not well optimized.",
+        ruleName: "no-dynamic-delete",
+        type: "functionality",
+        typescriptOnly: false,
+    };
+
+    public static FAILURE_STRING = "Do not delete dynamically computed property keys.";
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithFunction(sourceFile, walk);
+    }
+}
+
+function walk(context: Lint.WalkContext<void>) {
+    function checkDeleteAccessExpression(node: ts.Expression | undefined): void {
+        if (node === undefined || !tsutils.isElementAccessExpression(node)) {
+            return;
+        }
+
+        const { argumentExpression } = node;
+        if (argumentExpression === undefined || isNecessaryDynamicAccess(argumentExpression)) {
+            return;
+        }
+
+        const start = argumentExpression.getStart(context.sourceFile) - 1;
+        const width = argumentExpression.getWidth() + 2;
+        let fix: Lint.Replacement | undefined;
+
+        if (tsutils.isPrefixUnaryExpression(argumentExpression)) {
+            const convertedOperand = convertUnaryOperand(argumentExpression);
+            if (convertedOperand !== undefined) {
+                fix = Lint.Replacement.replaceFromTo(start, start + width, `[${convertedOperand}]`);
+            }
+        } else if (tsutils.isStringLiteral(argumentExpression)) {
+            fix = Lint.Replacement.replaceFromTo(start, start + width, `.${argumentExpression.text}`);
+        }
+
+        context.addFailureAt(start, width, Rule.FAILURE_STRING, fix);
+    }
+
+    return ts.forEachChild(context.sourceFile, function callback(node: ts.Node): void {
+        if (isDeleteExpression(node)) {
+            checkDeleteAccessExpression(node.expression);
+        }
+
+        return ts.forEachChild(node, callback);
+    });
+}
+
+function convertUnaryOperand(node: ts.PrefixUnaryExpression) {
+    return tsutils.isNumericLiteral(node.operand)
+        ? node.operand.text
+        : undefined;
+}
+
+function isDeleteExpression(node: ts.Node): node is ts.DeleteExpression {
+    return node.kind === ts.SyntaxKind.DeleteExpression;
+}
+
+function isNumberLike(node: ts.Node): boolean {
+    if (tsutils.isPrefixUnaryExpression(node)) {
+        return tsutils.isNumericLiteral(node.operand) && node.operator === ts.SyntaxKind.MinusToken;
+    }
+
+    return tsutils.isNumericLiteral(node);
+}
+
+function isNecessaryDynamicAccess(argumentExpression: ts.Expression): boolean {
+    if (isNumberLike(argumentExpression)) {
+        return true;
+    }
+
+    return tsutils.isStringLiteral(argumentExpression) && !tsutils.isValidPropertyAccess(argumentExpression.text);
+}

test/rules/no-dynamic-delete/test.ts.fix

@@ -0,0 +1,19 @@
+const container: { [i: string]: 0 } = {};
+
+const getName = () => "";
+
+delete container.aaa;
+delete container["bb" + "b"];
+delete container.ccc;
+delete container.delete;
+delete container.delete;
+delete container[7];
+delete container[-7];
+delete container[7];
+delete container[-Infinity];
+delete container["-Infinity"];
+delete container[+Infinity];
+delete container["+Infinity"];
+delete container[NaN];
+delete container.NaN;
+delete container[getName()];

test/rules/no-dynamic-delete/test.ts.lint

@@ -0,0 +1,29 @@
+const container: { [i: string]: 0 } = {};
+
+const getName = () => "";
+
+delete container.aaa;
+delete container["bb" + "b"];
+                ~~~~~~~~~~~~       [0]
+delete container["ccc"];
+                ~~~~~~~       [0]
+delete container.delete;
+delete container["delete"];
+                ~~~~~~~~~~       [0]
+delete container[7];
+delete container[-7];
+delete container[+7];
+                ~~~~       [0]
+delete container[-Infinity];
+                ~~~~~~~~~~~       [0]
+delete container["-Infinity"];
+delete container[+Infinity];
+                ~~~~~~~~~~~       [0]
+delete container["+Infinity"];
+delete container[NaN];
+                ~~~~~       [0]
+delete container["NaN"];
+                ~~~~~~~       [0]
+delete container[getName()];
+                ~~~~~~~~~~~       [0]
+[0]: Do not delete dynamically computed property keys.

test/rules/no-dynamic-delete/tslint.json

@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "no-dynamic-delete": true
+  }
+}