New rule: no-floating-promises

src/rules/noFloatingPromisesRule.ts

@@ -0,0 +1,104 @@
+/**
+ * @license
+ * Copyright 2016 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 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-floating-promises",
+        description: "Promises returned by functions must be handled appropriately.",
+        optionsDescription: Lint.Utils.dedent`
+            A list of \'string\' names of any additional classes that should also be handled as Promises.
+        `,
+        options: {
+            type: "list",
+            listType: {
+                type: "array",
+                items: {type: "string"},
+            },
+        },
+        optionExamples: ["true", `[true, "JQueryPromise"]`],
+        rationale: "Unhandled Promises can cause unexpected behavior, such as resolving at unexpected times.",
+        type: "functionality",
+        typescriptOnly: false,
+    };
+    /* tslint:enable:object-literal-sort-keys */
+
+    public static FAILURE_STRING = "Promises must be handled appropriately";
+
+    public applyWithProgram(sourceFile: ts.SourceFile, langSvc: ts.LanguageService): Lint.RuleFailure[] {
+        const walker = new NoFloatingPromisesWalker(sourceFile, this.getOptions(), langSvc.getProgram());
+
+        for (const className of this.getOptions().ruleArguments) {
+            walker.addPromiseClass(className);
+        }
+
+        return this.applyWithWalker(walker);
+    }
+}
+
+class NoFloatingPromisesWalker extends Lint.ProgramAwareRuleWalker {
+    private static barredParentKinds: { [x: number]: boolean } = {
+        [ts.SyntaxKind.Block]: true,
+        [ts.SyntaxKind.ExpressionStatement]: true,
+        [ts.SyntaxKind.SourceFile]: true,
+    };
+
+    private promiseClasses = ["Promise"];
+
+    public addPromiseClass(className: string) {
+        this.promiseClasses.push(className);
+    }
+
+    public visitCallExpression(node: ts.CallExpression): void {
+        this.checkNode(node);
+        super.visitCallExpression(node);
+    }
+
+    public visitExpressionStatement(node: ts.ExpressionStatement): void {
+        this.checkNode(node);
+        super.visitExpressionStatement(node);
+    }
+
+    private checkNode(node: ts.CallExpression | ts.ExpressionStatement) {
+        if (node.parent && this.kindCanContainPromise(node.parent.kind)) {
+            return;
+        }
+
+        const typeChecker = this.getTypeChecker();
+        const type = typeChecker.getTypeAtLocation(node);
+
+        if (this.symbolIsPromise(type.symbol)) {
+            this.addFailure(this.createFailure(node.getStart(), node.getWidth(), Rule.FAILURE_STRING));
+        }
+    }
+
+    private symbolIsPromise(symbol?: ts.Symbol) {
+        if (!symbol) {
+            return false;
+        }
+
+        return this.promiseClasses.indexOf(symbol.name) !== -1;
+    }
+
+    private kindCanContainPromise(kind: ts.SyntaxKind) {
+        return !NoFloatingPromisesWalker.barredParentKinds[kind];
+    }
+}

test/rules/no-floating-promises/jquerypromise/test.ts.lint

@@ -0,0 +1,17 @@
+class Promise { }
+class JQueryPromise { }
+class NotAPromise { }
+
+const returnsPromise = () => new Promise();
+const returnsJQueryPromise = () => new JQueryPromise();
+const returnsNotAPromise = () => new NotAPromise();
+
+returnsPromise();
+~~~~~~~~~~~~~~~~       [0]
+
+returnsJQueryPromise();
+~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+returnsNotAPromise();
+
+[0]: Promises must be handled appropriately

test/rules/no-floating-promises/jquerypromise/tslint.json

@@ -0,0 +1,8 @@
+{
+  "linterOptions": {
+    "typeCheck": true
+  },
+  "rules": {
+    "no-floating-promises": [true, "JQueryPromise"]
+  }
+}

test/rules/no-floating-promises/promises/test.ts.lint

@@ -0,0 +1,141 @@
+class Promise {
+    then(): Promise;
+}
+
+function returnsPromiseFunction() {
+    return new Promise();
+}
+
+const returnsPromiseVariable = () => new Promise();
+
+class ReturnsPromiseClass {
+    returnsPromiseMemberFunction() {
+        return new Promise();
+    }
+
+    returnsPromiseMemberVariable = () => new Promise();
+
+    static returnsPromiseStaticFunction = () => new Promise();
+}
+
+let a = returnsPromiseFunction();
+let b = returnsPromiseVariable();
+let c = new ReturnsPromiseClass().returnsPromiseMemberFunction();
+let d = new ReturnsPromiseClass().returnsPromiseMemberVariable();
+let e = ReturnsPromiseClass.returnsPromiseStaticFunction();
+
+returnsPromiseFunction();
+~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+returnsPromiseFunction().then();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+returnsPromiseVariable();
+~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+returnsPromiseVariable().then();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+new ReturnsPromiseClass().returnsPromiseMemberFunction();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+new ReturnsPromiseClass().returnsPromiseMemberFunction().then();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+new ReturnsPromiseClass().returnsPromiseMemberVariable();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+new ReturnsPromiseClass().returnsPromiseMemberVariable().then();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+ReturnsPromiseClass.returnsPromiseStaticFunction();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+ReturnsPromiseClass.returnsPromiseStaticFunction().then();
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+(function () {
+    let a = returnsPromiseFunction();
+
+    returnsPromiseFunction();
+    ~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    returnsPromiseFunction().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberFunction();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberFunction().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberVariable();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberVariable().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    ReturnsPromiseClass.returnsPromiseStaticFunction();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    ReturnsPromiseClass.returnsPromiseStaticFunction().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+})();
+
+(() => {
+    let a = returnsPromiseFunction();
+
+    returnsPromiseFunction();
+    ~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    returnsPromiseFunction().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberFunction();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberFunction().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberVariable();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    new ReturnsPromiseClass().returnsPromiseMemberVariable().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    ReturnsPromiseClass.returnsPromiseStaticFunction();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+
+    ReturnsPromiseClass.returnsPromiseStaticFunction().then();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~       [0]
+})();
+
+[].push(returnsPromiseFunction());
+
+[].push(returnsPromiseFunction().then());
+
+[].push(ReturnsPromiseClass.returnsPromiseStaticFunction());
+
+[].push(ReturnsPromiseClass.returnsPromiseStaticFunction().then());
+
+while (returnsPromiseFunction());
+
+while (returnsPromiseFunction().then());
+
+for (let i = 0; i < returnsPromiseFunction(); i += 1);
+
+for (let i = 0; i < returnsPromiseFunction().then(); i += 1);
+
+for (let i in returnsPromiseFunction());
+
+for (let i in returnsPromiseFunction().then());
+
+for (const promise of returnsPromiseFunction());
+
+for (const promise of returnsPromiseFunction().then());
+
+let promise = Math.random() > .5
+    ? returnsPromiseFunction()
+    : returnsPromiseFunction().then();
+
+[0]: Promises must be handled appropriately

test/rules/no-floating-promises/promises/tslint.json

@@ -0,0 +1,8 @@
+{
+  "linterOptions": {
+    "typeCheck": true
+  },
+  "rules": {
+    "no-floating-promises": true
+  }
+}