[new-rule] newline-per-chained-call (#3278)

src/configs/all.ts

@@ -198,6 +198,7 @@ export const rules = {
     "match-default-export-name": true,
     "new-parens": true,
     "newline-before-return": true,
+    "newline-per-chained-call": true,
     "no-angle-bracket-type-assertion": true,
     "no-boolean-literal-compare": true,
     "no-consecutive-blank-lines": true,

src/rules/newlinePerChainedCallRule.ts

@@ -0,0 +1,84 @@
+/**
+ * @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 {
+    isCallExpression,
+    isElementAccessExpression,
+    isPropertyAccessExpression,
+    isSameLine,
+} from "tsutils";
+import * as ts from "typescript";
+import * as Lint from "..";
+
+export class Rule extends Lint.Rules.AbstractRule {
+    /* tslint:disable:object-literal-sort-keys */
+    public static metadata: Lint.IRuleMetadata = {
+        ruleName: "newline-per-chained-call",
+        description: Lint.Utils.dedent`
+            Requires that chained method calls be broken apart onto separate lines.`,
+        rationale: Lint.Utils.dedent`
+            This style helps to keep code 'vertical', avoiding the need for side-scrolling in IDEs or text editors.`,
+        optionsDescription: "Not configurable",
+        options: null,
+        type: "style",
+        typescriptOnly: false,
+    };
+    /* tslint:enable:object-literal-sort-keys */
+    public static FAILURE_STRING = "When chaining calls, put method calls on new lines.";
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithWalker(
+            new NewlinePerChainedCallWalker(sourceFile, this.ruleName, undefined),
+        );
+    }
+}
+
+class NewlinePerChainedCallWalker extends Lint.AbstractWalker<void> {
+    public walk(sourceFile: ts.SourceFile) {
+        const checkForSameLine = (node: ts.Node): void => {
+            if (
+                isCallExpression(node) &&
+                isPropertyAccessExpression(node.expression) &&
+                isSameLine(
+                    sourceFile,
+                    node.expression.expression.end,
+                    node.expression.name.pos,
+                ) &&
+                hasChildCall(node.expression)
+            ) {
+                this.addFailure(
+                    node.expression.name.pos - 1,
+                    node.expression.name.end,
+                    Rule.FAILURE_STRING,
+                );
+            }
+            return ts.forEachChild(node, checkForSameLine);
+        };
+        return ts.forEachChild(sourceFile, checkForSameLine);
+    }
+}
+
+function hasChildCall(node: ts.PropertyAccessExpression): boolean {
+    let { expression } = node;
+    while (
+        isPropertyAccessExpression(expression) ||
+        isElementAccessExpression(expression)
+    ) {
+        ({ expression } = expression);
+    }
+    return expression.kind === ts.SyntaxKind.CallExpression;
+}

test/rules/newline-per-chained-call/default/test.ts.lint

@@ -0,0 +1,120 @@
+this.getFoo()[0].toString();
+                ~~~~~~~~~ [ERROR]
+
+this.foo()["bar"]().buzz();
+                   ~~~~~ [ERROR]
+
+this.foo()["bar"]();
+
+foo().bar();
+     ~~~~ [ERROR]
+
+const y: string[] = _observable
+                        .map(function(item) { return item.helloYay().another() }
+                                                                    ~~~~~~~~ [ERROR]
+                        .operator()    
+                        .another(function(result) { return result.hello.Yay! }).wrong();
+                                                                               ~~~~~~ [ERROR]
+
+SomeClass.propA.helloYay((a: number) => {
+    return a + 1;
+});
+
+this.some.nested();
+
+const y: string[] = _observable
+                        .map(function(item) { return item.helloYay! })
+                        .operator()    
+                        .another(function(result) { return result.hello.Yay! });
+
+
+const y: string[] = _observable.map(item => item.helloYay).operator().another(function(result) { return result.helloYay! });
+                                                                     ~~~~~~~~ [ERROR]
+                                                          ~~~~~~~~~ [ERROR]
+
+const x: string[] = _observable.map(item => item.helloYay);
+
+SomeClass.propA.propB.helloYay();
+
+SomeClass
+    .propA
+    .propB
+    .helloYay();
+
+SomeClass
+    .propA
+    .propB.helloYay();
+
+SomeClass
+    .propA
+    .propB
+    .helloYay(function() {
+        return 1;
+    }).test();
+      ~~~~~ [ERROR]
+
+SomeClass
+    .propA
+    .propB
+    .helloYay(function() {
+        return 1;
+    }).  test();
+      ~~~~~~~ [ERROR]
+
+SomeClass
+    .propA
+    .propB
+    .helloYay(function() {
+        return 1;
+    }).
+      ~
+    test();
+~~~~~~~~ [ERROR]
+
+SomeClass.propA.propB.methodB(() => {
+    return "hello Yay!";
+}).helloYay((a: number) => {
+  ~~~~~~~~~ [ERROR]
+    return a + 1;
+});
+
+SomeClass.propA.propB.methodB(() => {
+    return "hello Yay!";
+})
+.helloYay((a: number) => {
+    return a + 1;
+});
+
+SomeClass.propA.propB.methodB(() => {
+    return "hello Yay!";
+})
+.helloYay((a: number) => {
+    return obj.method()
+                .chainedButOkay(
+                    objB.nested().superNestedCall()
+                                 ~~~~~~~~~~~~~~~~ [ERROR]
+                )
+});
+
+SomeClass.propA.propB.methodB(() => {
+    return "hello Yay!";
+})
+.helloYay((a: number) => {
+    return obj.method()
+                .chainedButOkay(
+                    objB.nested()
+                        .superNestedCall()
+                )
+});
+
+SomeClass
+    .propA
+    .propB
+    .methodC(() => {
+        return "hello Yay!";
+    })
+    .helloYay(() => {
+        return 1;
+    });
+
+[ERROR]: When chaining calls, put method calls on new lines.

test/rules/newline-per-chained-call/default/tslint.json

@@ -0,0 +1,5 @@
+{
+    "rules": {
+        "newline-per-chained-call": true
+    }
+}

tslint.json

@@ -54,6 +54,7 @@
       "static-before-instance",
       "variables-before-functions"
     ],
+    "newline-per-chained-call": false,
     "no-console": {
       "options": ["log"]
     },