New Rule: param-property-in-constructor

README.md

@@ -335,6 +335,7 @@ Core rules are included in the `tslint` package.
 * `one-variable-per-declaration` disallows multiple variable definitions in the same statement.
   * `"ignore-for-loop"` allows multiple variable definitions in for loop statement.
 * `only-arrow-functions` disallows traditional `function () { ... }` declarations, preferring `() => { ... }` arrow lambdas.
+* `param-property-in-constructor` Disallows `private`, `public`, or `protected` constructor parameter properties to be accessed without the `this.` prefix.
 * `quotemark` enforces consistent single or double quoted string literals. Rule options (at least one of `"double"` or `"single"` is required):
     * `"single"` enforces single quotes.
     * `"double"` enforces double quotes.

src/rules/paramPropertyInConstructorRule.ts

@@ -0,0 +1,96 @@
+/**
+ * @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 * as Lint from "../lint";
+import * as ts from "typescript";
+
+export class Rule extends Lint.Rules.AbstractRule {
+    /* tslint:disable:object-literal-sort-keys */
+    public static metadata: Lint.IRuleMetadata = {
+        ruleName: "param-property-in-constructor",
+        description: "Disallows constructor parameter properties to be accessed without the 'this.' prefix",
+        rationale: Lint.Utils.dedent`
+            This helps enforce consistancy.
+            When a constructor parameter is accessed without the 'this.' prefix, it is actually not acessing the same thing.
+            Example: 
+            class Foo {
+                constructor(public num: number) {
+                    this.num = 10;
+                    num = 5;  //this should be disallowed!
+                }
+            }
+            const f = new Foo();
+            alert(f.num);  // will display 10`,
+        optionsDescription: "Not configurable.",
+        options: null,
+        optionExamples: ["true"],
+        type: "functionality",
+    };
+    /* tslint:enable:object-literal-sort-keys */
+
+    public static FAILURE_STRING_FACTORY = (paramName: string) => {
+        return `The constructor parameter '${paramName}' should only be accessed with the 'this' keyword: 'this.${paramName}'`;
+    }
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        const languageService = Lint.createLanguageService(sourceFile.fileName, sourceFile.getFullText());
+        return this.applyWithWalker(new ParamPropInCtorWalker(sourceFile, this.getOptions(), languageService));
+    }
+}
+
+export class ParamPropInCtorWalker extends Lint.RuleWalker {
+
+    constructor(sourceFile: ts.SourceFile, options: Lint.IOptions, private languageService: ts.LanguageService) {
+        super(sourceFile, options);
+        this.languageService = languageService;
+    }
+
+    public visitConstructorDeclaration(node: ts.ConstructorDeclaration) {
+        if (node.parameters && node.parameters.length > 0) {
+            const fileName = this.getSourceFile().fileName;
+            for (let param of node.parameters) {
+                if (param.modifiers != null && param.modifiers.length > 0) {
+                    this.validateParam(param, fileName);
+                }
+            }
+        }
+        super.visitConstructorDeclaration(node);
+    }
+
+    private validateParam(param: ts.ParameterDeclaration, fileName: string) {
+        const highlights = this.languageService.getDocumentHighlights(fileName, param.name.getStart(), [fileName]);
+
+        if ((highlights !== null && highlights[0].highlightSpans.length > 0)) {
+            const paramName = param.name.getText();
+            highlights[0].highlightSpans.forEach((span: ts.HighlightSpan, idx: number) => {
+                // Ignore the 1st reference which is the actual parameter definition
+                if (idx !== 0 && !this.spanHasThisUsage(span, fileName)) {
+                    const msg = Rule.FAILURE_STRING_FACTORY(paramName);
+                    this.addFailure(this.createFailure(span.textSpan.start, span.textSpan.length, msg));
+                }
+            });
+        }
+    }
+
+    private spanHasThisUsage(span: ts.HighlightSpan, fileName: string) {
+        const endPos = span.textSpan.start + span.textSpan.length;
+        const nameSpanInfo = this.languageService.getNameOrDottedNameSpan(fileName, span.textSpan.start, endPos);
+
+        // If the difference between these two is exactly 5 characters it accounts for the missing `this.`!
+        return nameSpanInfo.length - span.textSpan.length === 5;
+    }
+}

src/tsconfig.json

@@ -129,6 +129,7 @@
         "rules/oneVariablePerDeclarationRule.ts",
         "rules/onlyArrowFunctionsRule.ts",
         "rules/orderedImportsRule.ts",
+        "rules/paramPropertyInConstructorRule.ts",
         "rules/quotemarkRule.ts",
         "rules/radixRule.ts",
         "rules/restrictPlusOperandsRule.ts",

test/rules/param-property-in-constructor/test.ts.lint

@@ -0,0 +1,65 @@
+class FailingExample1 {
+    constructor(fruit: string, public num: number, private animal: string, protected mineral: string) {
+        //Both usage here are OK since `fruit` is a regular parameter and not a class property
+        fruit = "banana";
+        this.fruit = "persimmon";
+
+        this.num = 10;
+        num = 5;
+        ~~~ [The constructor parameter 'num' should only be accessed with the 'this' keyword: 'this.num']
+
+        animal = "aardvark";
+        ~~~~~~ [The constructor parameter 'animal' should only be accessed with the 'this' keyword: 'this.animal']
+        this.animal = "skunk";
+
+        mineral = "Gypsum";
+        ~~~~~~~ [The constructor parameter 'mineral' should only be accessed with the 'this' keyword: 'this.mineral']
+        this.mineral = "Fluorite";
+    }
+}
+
+class FailingExample2 {
+    constructor(public thing: Object) {
+        const wow=thing.doTheThing()
+                  ~~~~~ [The constructor parameter 'thing' should only be accessed with the 'this' keyword: 'this.thing']
+        console.log(wow, thing.amazingDvdCollection);
+                         ~~~~~ [The constructor parameter 'thing' should only be accessed with the 'this' keyword: 'this.thing']
+
+        const pasta = thing.nested.makePasta();
+                      ~~~~~ [The constructor parameter 'thing' should only be accessed with the 'this' keyword: 'this.thing']
+
+        thing = {};
+        ~~~~~ [The constructor parameter 'thing' should only be accessed with the 'this' keyword: 'this.thing']
+
+        this.thing.doSomethingElse();
+    }
+}
+
+class PassingExample1 {
+    //This is OK since `thing` is a regular parameter and not a class property here
+    constructor(thing: Object) {
+        const wow=thing.doTheThing()
+        console.log(wow,thing.amazingDvdCollection);
+        const pasta = thing.nested.makePasta();
+        thing = {};
+        this.thing.doSomethingElse();
+    }
+}
+
+class PassingExample2 {
+    constructor(a: string, private b: string, public c: string, protected d: string) {
+        this.a = "aaa";
+        this.b = "bbb";
+        this.c = "ccc";
+        this.d = "ddd";
+    }
+}
+
+class PassingExample3 {
+    constructor(a: Object, private b: Object, public c: Object, protected d: Object) {
+        this.a.doThing();
+        this.b.doOtherThing();
+        this.c.doAnotherThing();
+        this.d.doLastThing();
+    }
+}

test/rules/param-property-in-constructor/tslint.json

@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "param-property-in-constructor": true
+  }
+}

test/tsconfig.json

@@ -125,6 +125,7 @@
         "../src/rules/oneVariablePerDeclarationRule.ts",
         "../src/rules/onlyArrowFunctionsRule.ts",
         "../src/rules/orderedImportsRule.ts",
+        "../src/rules/paramPropertyInConstructorRule.ts",
         "../src/rules/quotemarkRule.ts",
         "../src/rules/radixRule.ts",
         "../src/rules/restrictPlusOperandsRule.ts",