fix(compat): deprecate Observable.if/throw (#3527)

* fix(compat): deprecate Observable.if/throw

* build: point circular deps check against output files

.dependency-cruiser.json

@@ -97,7 +97,7 @@
       "severity": "error",
       "comment": "Error in case we have circular dependencies",
       "from": {
-        "path": "^src"
+        "path": "^dist/esm5"
       },
       "to": {
         "circular": true

compat/add/observable/if.ts

@@ -1,4 +1,3 @@
 import { Observable, iif } from 'rxjs';
 
-//tslint:disable-next-line:no-any TypeScript doesn't like `if`
-(Observable as any).if = iif;
+Observable.if = iif;

compat/add/observable/throw.ts

@@ -1,6 +1,6 @@
 import { Observable, throwError as staticThrowError } from 'rxjs';
 
-(Observable as any).throw = staticThrowError;
+Observable.throw = staticThrowError;
 Observable.throwError = staticThrowError;
 
 declare module 'rxjs/internal/Observable' {

package.json

@@ -119,7 +119,7 @@
     "test_browser": "npm-run-all build_spec_browser && opn spec/support/mocha-browser-runner.html",
     "test": "mocha --require ts-node/register --opts spec-build/support/coverage.opts \"spec-build/**/*-spec.ts\"",
     "test:cover": "cross-env TS_NODE_FAST=true nyc npm test",
-    "test:circular": "dependency-cruise --validate .dependency-cruiser.json -x \"^node_modules\" src",
+    "test:circular": "dependency-cruise --validate .dependency-cruiser.json -x \"^node_modules\" dist/esm5",
     "test:systemjs": "node integration/systemjs/systemjs-compatibility-spec.js",
     "tests2png": "mkdirp tmp/docs/img && cross-env TS_NODE_FAST=true mocha --compilers ts:ts-node/register --opts spec/support/tests2png.opts \"spec/**/*-spec.ts\"",
     "watch": "watch \"echo triggering build && npm run build_spec && npm run test && echo build completed\" src -d -u -w=15",

src/internal/Observable.ts

@@ -4,6 +4,7 @@ import { Subscription } from './Subscription';
 import { TeardownLogic } from './types';
 import { toSubscriber } from './util/toSubscriber';
 import { iif } from './observable/iif';
+import { throwError } from './observable/throwError';
 import { observable as Symbol_observable } from '../internal/symbol/observable';
 import { OperatorFunction, PartialObserver, Subscribable } from '../internal/types';
 import { pipeFromArray } from './util/pipe';
@@ -252,10 +253,18 @@ export class Observable<T> implements Subscribable<T> {
     return source && source.subscribe(subscriber);
   }
 
-  // TODO(benlesh): determine if this is still necessary
-  // `if` and `throw` are special snow flakes, the compiler sees them as reserved words
-  /** @nocollapse */
+  // `if` and `throw` are special snow flakes, the compiler sees them as reserved words. Deprecated in
+  // favor of iif and throwError functions.
+  /**
+   * @nocollapse
+   * @deprecated In favor of iif creation function: import { iif } from 'rxjs';
+   */
   static if: typeof iif;
+  /**
+   * @nocollapse
+   * @deprecated In favor of throwError creation function: import { throwError } from 'rxjs';
+   */
+  static throw: typeof throwError;
 
   /**
    * An interop point defined by the es7-observable spec https://github.com/zenparsing/es-observable