forked from palantir/tslint
/
noUnboundMethodRule.ts
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/
noUnboundMethodRule.ts
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/**
* @license
* Copyright 2017 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 {
hasModifier,
isCallExpression,
isDeleteExpression,
isIdentifier,
isPropertyAccessExpression,
isTypeOfExpression,
} from "tsutils";
import * as ts from "typescript";
import * as Lint from "../index";
const OPTION_IGNORE_STATIC = "ignore-static";
const OPTION_WHITELIST = "whitelist";
const OPTION_ALLOW_TYPEOF = "allow-typeof";
const OPTION_ALLOW_DELETE = "allow-delete";
const OPTION_WHITELIST_EXAMPLE = [
true,
{
[OPTION_IGNORE_STATIC]: true,
[OPTION_WHITELIST]: ["expect"],
[OPTION_ALLOW_TYPEOF]: true,
},
];
interface Options {
allowDelete: boolean;
allowTypeof: boolean;
ignoreStatic: boolean;
whitelist: Set<string>;
}
interface OptionsInput {
[OPTION_ALLOW_DELETE]?: boolean;
[OPTION_ALLOW_TYPEOF]?: boolean;
[OPTION_IGNORE_STATIC]?: boolean;
[OPTION_WHITELIST]?: string[];
}
export class Rule extends Lint.Rules.TypedRule {
/* tslint:disable:object-literal-sort-keys */
public static metadata: Lint.IRuleMetadata = {
ruleName: "no-unbound-method",
description: "Warns when a method is used outside of a method call.",
optionsDescription: Lint.Utils.dedent`
You may additionally pass "${OPTION_IGNORE_STATIC}" to ignore static methods, or an options object.
The object may have the following properties:
* "${OPTION_IGNORE_STATIC}" - to ignore static methods.
* "${OPTION_ALLOW_DELETE}" - ignore methods referenced in a delete expression.
* "${OPTION_ALLOW_TYPEOF}" - ignore methods referenced in a typeof expression.
* "${OPTION_WHITELIST}" - ignore method references in parameters of specifed function calls.
`,
options: {
anyOf: [
{
type: "string",
enum: [OPTION_IGNORE_STATIC],
},
{
type: "object",
properties: {
[OPTION_ALLOW_DELETE]: { type: "boolean" },
[OPTION_ALLOW_TYPEOF]: { type: "boolean" },
[OPTION_IGNORE_STATIC]: { type: "boolean" },
[OPTION_WHITELIST]: {
type: "array",
items: { type: "string" },
minLength: 1,
},
},
},
],
},
optionExamples: [true, [true, OPTION_IGNORE_STATIC], OPTION_WHITELIST_EXAMPLE],
rationale: Lint.Utils.dedent`
Class functions don't preserve the class scope when passed as standalone variables.
For example, this code will log the global scope (\`window\`/\`global\`), not the class instance:
\`\`\`
class MyClass {
public log(): void {
console.log(this);
}
}
const instance = new MyClass();
const log = instance.log;
log();
\`\`\`
You need to either use an arrow lambda (\`() => {...}\`) or call the function with the correct scope.
\`\`\`
class MyClass {
public logArrowBound = (): void => {
console.log(bound);
};
public logManualBind(): void {
console.log(this);
}
}
const instance = new MyClass();
const logArrowBound = instance.logArrowBound;
const logManualBind = instance.logManualBind.bind(instance);
logArrowBound();
logManualBind();
\`\`\`
`,
type: "functionality",
typescriptOnly: true,
requiresTypeInfo: true,
};
/* tslint:enable:object-literal-sort-keys */
public static FAILURE_STRING =
"Avoid referencing unbound methods which may cause unintentional scoping of 'this'.";
public applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
return this.applyWithFunction(
sourceFile,
walk,
parseArguments(this.ruleArguments),
program.getTypeChecker(),
);
}
}
function parseArguments(args: Array<string | OptionsInput>): Options {
const options: Options = {
allowDelete: false,
allowTypeof: false,
ignoreStatic: false,
whitelist: new Set(),
};
for (const arg of args) {
if (typeof arg === "string") {
if (arg === OPTION_IGNORE_STATIC) {
options.ignoreStatic = true;
}
} else {
options.allowDelete = arg[OPTION_ALLOW_DELETE] || false;
options.allowTypeof = arg[OPTION_ALLOW_TYPEOF] || false;
options.ignoreStatic = arg[OPTION_IGNORE_STATIC] || false;
options.whitelist = new Set(arg[OPTION_WHITELIST]);
}
}
return options;
}
function walk(ctx: Lint.WalkContext<Options>, tc: ts.TypeChecker) {
return ts.forEachChild(ctx.sourceFile, function cb(node): void {
if (isPropertyAccessExpression(node) && !isSafeUse(node)) {
const symbol = tc.getSymbolAtLocation(node);
const declaration = symbol === undefined ? undefined : symbol.valueDeclaration;
const isMethodAccess =
declaration !== undefined && isMethod(declaration, ctx.options.ignoreStatic);
const shouldBeReported = isMethodAccess && !isWhitelisted(node, ctx.options);
if (shouldBeReported) {
ctx.addFailureAtNode(node, Rule.FAILURE_STRING);
}
}
return ts.forEachChild(node, cb);
});
}
function isMethod(node: ts.Node, ignoreStatic: boolean): boolean {
switch (node.kind) {
case ts.SyntaxKind.MethodDeclaration:
case ts.SyntaxKind.MethodSignature:
return !(ignoreStatic && hasModifier(node.modifiers, ts.SyntaxKind.StaticKeyword));
default:
return false;
}
}
function isSafeUse(node: ts.Node): boolean {
const parent = node.parent;
switch (parent.kind) {
case ts.SyntaxKind.CallExpression:
return (parent as ts.CallExpression).expression === node;
case ts.SyntaxKind.TaggedTemplateExpression:
return (parent as ts.TaggedTemplateExpression).tag === node;
// E.g. `obj.method.bind(obj) or obj.method["prop"]`.
case ts.SyntaxKind.PropertyAccessExpression:
case ts.SyntaxKind.ElementAccessExpression:
return true;
// Allow most binary operators, but don't allow e.g. `myArray.forEach(obj.method || otherObj.otherMethod)`.
case ts.SyntaxKind.BinaryExpression:
return (parent as ts.BinaryExpression).operatorToken.kind !== ts.SyntaxKind.BarBarToken;
case ts.SyntaxKind.NonNullExpression:
case ts.SyntaxKind.AsExpression:
case ts.SyntaxKind.TypeAssertionExpression:
case ts.SyntaxKind.ParenthesizedExpression:
return isSafeUse(parent);
// Allow use in conditions
case ts.SyntaxKind.ConditionalExpression:
return (parent as ts.ConditionalExpression).condition === node;
case ts.SyntaxKind.IfStatement:
case ts.SyntaxKind.WhileStatement:
case ts.SyntaxKind.DoStatement:
case ts.SyntaxKind.ForStatement:
case ts.SyntaxKind.PrefixUnaryExpression:
return true;
default:
return false;
}
}
function isWhitelisted(node: ts.Node, options: Options): boolean {
const { whitelist, allowTypeof, allowDelete } = options;
if (isDeleteExpression(node.parent)) {
return allowDelete;
}
if (isTypeOfExpression(node.parent)) {
return allowTypeof;
}
if (isCallExpression(node.parent) && isIdentifier(node.parent.expression)) {
const expression = node.parent.expression;
const callingMethodName = expression.text;
return whitelist.has(callingMethodName);
}
return false;
}