feat(no-subject-value): Add BehaviorSubject rule.

README.md

@@ -80,7 +80,8 @@ The package includes the following rules (none of which are enabled by default):
 | `rxjs-no-ignored-subscribe` | Disallows the calling of subscribe without specifying arguments. | None |
 | `rxjs-no-operator` | Disallows importation from the `operator` directory. Useful if you prefer ['lettable' operators](https://github.com/ReactiveX/rxjs/blob/master/doc/lettable-operators.md) - which are located in the `operators` directory. | None |
 | `rxjs-no-patched` | Disallows the calling of patched methods. Methods must be imported and called explicitly - not via `Observable` or `Observable.prototype`. | See below |
-| `rxjs-no-subject-unsubscribe` | Disallows the calling of `unsubscribe` directly upon `Subject` instances. For an explanation of why this can be a problem, see [this](https://stackoverflow.com/a/45112125/6680611) Stack Overflow answer. | None |
+| `rxjs-no-subject-unsubscribe` | Disallows calling the `unsubscribe` method of a `Subject` instance. For an explanation of why this can be a problem, see [this](https://stackoverflow.com/a/45112125/6680611) Stack Overflow answer. | None |
+| `rxjs-no-subject-value` | Disallows accessing the `value` property of a `BehaviorSubject` instance. | None |
 | `rxjs-no-tap` | An alias for `rxjs-no-do`. | None |
 | `rxjs-no-unused-add` | Disallows the importation of patched observables or operators that are not used in the module. | None |
 | `rxjs-no-wholesale` | Disallows the wholesale importation of `rxjs` or `rxjs/Rx`. | None |

docs/index.md

@@ -20,7 +20,8 @@ The package includes the following rules (none of which are enabled by default):
 | `rxjs-no-ignored-subscribe` | Disallows the calling of subscribe without specifying arguments. | None |
 | `rxjs-no-operator` | Disallows importation from the `operator` directory. Useful if you prefer ['lettable' operators](https://github.com/ReactiveX/rxjs/blob/master/doc/lettable-operators.md) - which are located in the `operators` directory. | None |
 | `rxjs-no-patched` | Disallows the calling of patched methods. Methods must be imported and called explicitly - not via `Observable` or `Observable.prototype`. | See below |
-| `rxjs-no-subject-unsubscribe` | Disallows the calling of `unsubscribe` directly upon `Subject` instances. For an explanation of why this can be a problem, see [this](https://stackoverflow.com/a/45112125/6680611) Stack Overflow answer. | None |
+| `rxjs-no-subject-unsubscribe` | Disallows calling the `unsubscribe` method of a `Subject` instance. For an explanation of why this can be a problem, see [this](https://stackoverflow.com/a/45112125/6680611) Stack Overflow answer. | None |
+| `rxjs-no-subject-value` | Disallows accessing the `value` property of a `BehaviorSubject` instance. | None |
 | `rxjs-no-tap` | An alias for `rxjs-no-do`. | None |
 | `rxjs-no-unused-add` | Disallows the importation of patched observables or operators that are not used in the module. | None |
 | `rxjs-no-wholesale` | Disallows the wholesale importation of `rxjs` or `rxjs/Rx`. | None |

fixtures/behavior-subject-value/fixture.ts

@@ -0,0 +1,5 @@
+import { BehaviorSubject } from "rxjs/BehaviorSubject";
+
+const subject = new BehaviorSubject<number>(1);
+console.log(subject.value);
+console.log(subject.getValue());

fixtures/behavior-subject-value/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "baseUrl": ".",
+    "lib": ["es2015"],
+    "noEmit": true,
+    "paths": {
+      "rxjs": ["../node_modules/rxjs"]
+    },
+    "skipLibCheck": true,
+    "target": "es5"
+  },
+  "include": ["fixture.ts"]
+}

fixtures/behavior-subject-value/tslint.json

@@ -0,0 +1,8 @@
+{
+  "defaultSeverity": "error",
+  "jsRules": {},
+  "rules": {
+    "rxjs-no-subject-value": { "severity": "error" }
+  },
+  "rulesDirectory": "../../build/rules"
+}

source/fixtures-spec.ts

@@ -489,6 +489,17 @@ describe("fixtures", function (): void {
             });
         });
 
+        describe("behavior-subject-value", () => {
+
+            it("should effect an 'rxjs-no-subject-value' error", () => {
+
+                const result = lint("behavior-subject-value", "tslint.json");
+
+                expect(result).to.have.property("errorCount", 2);
+                result.failures.forEach(failure => expect(failure).to.have.property("ruleName", "rxjs-no-subject-value"));
+            });
+        });
+
         describe("subject-add-subscription", () => {
 
             it("should effect an 'rxjs-no-subject-unsubscribe' error", () => {

source/rules/rxjsNoSubjectUnsubscribeRule.ts

@@ -12,7 +12,7 @@ import { couldBeType, isReferenceType } from "../support/util";
 export class Rule extends Lint.Rules.TypedRule {
 
     public static metadata: Lint.IRuleMetadata = {
-        description: "Disallows the calling of unsubscribe directly upon subject instances.",
+        description: "Disallows calling the unsubscribe method of a subject instance.",
         options: null,
         optionsDescription: "Not configurable.",
         requiresTypeInfo: true,
@@ -21,7 +21,7 @@ export class Rule extends Lint.Rules.TypedRule {
         typescriptOnly: true
     };
 
-    public static FAILURE_STRING = "Calling unsubscribe on subjects is forbidden";
+    public static FAILURE_STRING = "Calling unsubscribe on a subject is forbidden";
 
     public applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
 

source/rules/rxjsNoSubjectValueRule.ts

@@ -0,0 +1,53 @@
+/**
+ * @license Use of this source code is governed by an MIT-style license that
+ * can be found in the LICENSE file at https://github.com/cartant/rxjs-tslint-rules
+ */
+/*tslint:disable:no-use-before-declare*/
+
+import * as Lint from "tslint";
+import * as ts from "typescript";
+
+import { couldBeType, isReferenceType } from "../support/util";
+
+export class Rule extends Lint.Rules.TypedRule {
+
+    public static metadata: Lint.IRuleMetadata = {
+        description: "Disallows accessing the value property of a BehaviorSubject instance.",
+        options: null,
+        optionsDescription: "Not configurable.",
+        requiresTypeInfo: true,
+        ruleName: "rxjs-no-subject-value",
+        type: "functionality",
+        typescriptOnly: true
+    };
+
+    public static FAILURE_STRING = "Accessing the value property of a BehaviorSubject is forbidden";
+
+    public applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
+
+        return this.applyWithWalker(new Walker(sourceFile, this.getOptions(), program));
+    }
+}
+
+export class Walker extends Lint.ProgramAwareRuleWalker {
+
+    protected visitCallExpression(node: ts.CallExpression): void {
+
+        node.forEachChild((child) => {
+
+            if (child.kind === ts.SyntaxKind.PropertyAccessExpression) {
+
+                const propertyAccessExpression = child as ts.PropertyAccessExpression;
+                const name = propertyAccessExpression.name.getText();
+                const typeChecker = this.getTypeChecker();
+                const type = typeChecker.getTypeAtLocation(propertyAccessExpression.expression);
+
+                if (((name === "value") || (name === "getValue")) && isReferenceType(type) && couldBeType(type.target, "BehaviorSubject")) {
+                    this.addFailureAtNode(propertyAccessExpression.name, Rule.FAILURE_STRING);
+                }
+            }
+        });
+
+        super.visitCallExpression(node);
+    }
+}