fix(unused): Support flatMap.

fixtures/flat-map/fixture.ts

@@ -0,0 +1,5 @@
+import { Observable } from "rxjs/Observable";
+import "rxjs/add/observable/of";
+import "rxjs/add/operator/mergeMap";
+
+const ob = Observable.of(1).flatMap((value) => [value + 1]);

fixtures/flat-map/tsconfig.json

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

source/fixtures-spec.ts

@@ -67,6 +67,16 @@ describe("fixtures", function (): void {
             });
         });
 
+        describe("flat-map", () => {
+
+            it("should effect no errors", () => {
+
+                const result = lint("flat-map");
+
+                expect(result).to.have.property("errorCount", 0);
+            });
+        });
+
         describe("import-wholesale", () => {
 
             it("should effect 'rxjs-no-wholesale' errors", () => {

source/support/knowns.ts

@@ -9,36 +9,43 @@ import * as path from "path";
 import * as resolve from "resolve";
 import * as semver from "semver";
 
-function read(dir: string): { [key: string]: boolean } {
-
-    let entry;
-    try {
-        entry = resolve.sync("rxjs");
-    } catch (error) {
-        /*tslint:disable-next-line:no-console*/
-        console.warn("Cannot find rxjs in node_modules; some rxjs-tslint-rules will be ineffectual.");
+let aliasOperators: { [key: string]: string } = { flatMap: "mergeMap" };
+let dist: string | undefined = undefined;
+let prototypeMethods: { [key: string]: boolean } = {};
+
+try {
+
+    const entry = resolve.sync("rxjs");
+    dist = path.dirname(entry);
+
+    const root = dist.replace(/node_modules[\/\\]rxjs[\/\\](.*)$/, (match) => match);
+    const { version } = require(path.join(root, "package.json"));
+    prototypeMethods = semver.satisfies(version, "<5.5.0-beta.5") ? {} : { pipe: true, toPromise: true };
+
+} catch (error) {
+    /*tslint:disable-next-line:no-console*/
+    console.warn("Cannot find rxjs in node_modules; some rxjs-tslint-rules will be ineffectual.");
+}
+
+function read(dir: string): { [key: string]: string } {
+
+    if (!dist) {
         return {};
     }
 
-    const dist = path.dirname(entry);
-
     // In RxJS 5.5.0-beta.5, toPromise was moved into the prototype.
     // However, to avoid breakage, the file in the add/operator directory was
     // left in-place.
 
-    const root = dist.replace(/node_modules[\/\\]rxjs[\/\\](.*)$/, (match) => match);
-    const { version } = require(path.join(root, "package.json"));
-    const ignored = semver.satisfies(version, "<5.5.0-beta.5") ? {} : { "toPromise": true };
-
     const names = fs.readdirSync(path.join(dist, dir));
     return names
         .filter((name) => /^[a-z]\w+\.js$/.test(name))
         .map((name) => name.replace(/\.js/, ""))
-        .filter((name) => !ignored[name])
-        .reduce((acc, name) => ({ ...acc, [name]: true }), {});
+        .filter((name) => !prototypeMethods[name])
+        .reduce((acc, name) => ({ ...acc, [name]: name }), {});
 }
 
 export const knownObservables = read("add/observable");
-export const knownOperators = read("add/operator");
-export const knownPrototypeMethods = { pipe: true, toPromise: true };
+export const knownOperators = { ...read("add/operator"), ...aliasOperators };
+export const knownPrototypeMethods = { forEach: true, ...prototypeMethods };
 export const knownStaticMethods = { create: true };

source/support/used-walker.ts

@@ -30,13 +30,15 @@ export class UsedWalker extends AddedWalker {
 
                 if (isReferenceType(type)) {
                     if (knownOperators.hasOwnProperty(name) && couldBeType(type.target, "Observable")) {
-                        UsedWalker.add(this.usedOperators, name, propertyAccessExpression.name);
+                        const actual = knownOperators[name];
+                        UsedWalker.add(this.usedOperators, actual, propertyAccessExpression.name);
                     } else if (knownPrototypeMethods.hasOwnProperty(name) && couldBeType(type.target, "Observable")) {
                         UsedWalker.add(this.usedPrototypeMethods, name, propertyAccessExpression.name);
                     }
                 } else {
                     if (knownObservables.hasOwnProperty(name) && couldBeType(type, "Observable")) {
-                        UsedWalker.add(this.usedObservables, name, propertyAccessExpression.name);
+                        const actual = knownObservables[name];
+                        UsedWalker.add(this.usedObservables, actual, propertyAccessExpression.name);
                     } else if (knownStaticMethods.hasOwnProperty(name) && couldBeType(type, "Observable")) {
                         UsedWalker.add(this.usedStaticMethods, name, propertyAccessExpression.name);
                     }