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noRestrictedGlobalsRule.ts
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noRestrictedGlobalsRule.ts
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/**
* @license
* Copyright 2014 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 {
isBindingElement,
isComputedPropertyName,
isIdentifier,
isPropertyAccessExpression,
} from "tsutils";
import * as ts from "typescript";
import * as Lint from "../index";
export class Rule extends Lint.Rules.TypedRule {
/* tslint:disable:object-literal-sort-keys */
public static metadata: Lint.IRuleMetadata = {
ruleName: "no-restricted-globals",
description: "Disallow specific global variables.",
rationale: Lint.Utils.dedent`
\`\`\`ts
function broken(evt: Event) {
// Meant to do something with \`evt\` but typed it incorrectly.
Event.target; // compiler error
event.target; // should be a lint failure
}
Early Internet Explorer versions exposed the current DOM event as a global variable 'event',
but using this variable has been considered a bad practice for a long time.
Restricting this will make sure this variable isn’t used in browser code.
\`\`\`
`,
descriptionDetails: Lint.Utils.dedent`
Disallowing usage of specific global variables can be useful if you want to allow
a set of global variables by enabling an environment, but still want to disallow
some of those.
`,
optionsDescription: Lint.Utils.dedent`
This rule takes a list of strings, where each string is a global to be restricted.
\`event\`, \`name\` and \`length\` are restricted by default.
`,
options: {
type: "list",
items: { type: "string" },
},
optionExamples: [[true, "name", "length", "event"]],
type: "functionality",
typescriptOnly: false,
requiresTypeInfo: true,
};
/* tslint:enable:object-literal-sort-keys */
public static FAILURE_STRING(name: string) {
return `Unexpected global variable '${name}'. Use a local parameter or variable instead.`;
}
public applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
const bannedList =
this.ruleArguments.length > 0 ? this.ruleArguments : ["event", "name", "length"];
const bannedGlobals = new Set(bannedList);
if (sourceFile.isDeclarationFile) {
return [];
} else {
return this.applyWithFunction(
sourceFile,
walk,
bannedGlobals,
program.getTypeChecker(),
);
}
}
}
function walk(ctx: Lint.WalkContext<Set<string>>, checker: ts.TypeChecker): void {
return ts.forEachChild(ctx.sourceFile, function recur(node: ts.Node | undefined): void {
if (node == undefined) {
return;
}
// Handles `const { bar, length: { x: y = () => event } } = foo`
if (isBindingElement(node)) {
recur(node.initializer);
recur(node.name);
if (node.propertyName != undefined && isComputedPropertyName(node.propertyName)) {
recur(node.propertyName);
}
} else if (isPropertyAccessExpression(node)) {
// Ignore `y` in `x.y`, but recurse to `x`.
recur(node.expression);
} else if (isIdentifier(node)) {
checkIdentifier(node);
} else {
ts.forEachChild(node, recur);
}
});
function checkIdentifier(node: ts.Identifier): void {
if (!ctx.options.has(node.text)) {
return;
}
const symbol = checker.getSymbolAtLocation(node);
const declarations = symbol === undefined ? undefined : symbol.declarations;
if (declarations === undefined || declarations.length === 0) {
return;
}
const isAmbientGlobal = declarations.some(decl => decl.getSourceFile().isDeclarationFile);
if (isAmbientGlobal) {
ctx.addFailureAtNode(node, Rule.FAILURE_STRING(node.text));
}
}
}