Final pass

I think I've got it now. I'm now interpreting it as defaultValue instead
of initialValue, which helps a lot. I also added deprecation warnings
for <Broadcast> and <Subscriber> which should help people upgrade.

Only remaining question for me is: can I ship code that uses Symbol() to
the browser? Do I need a shim for that?

Author: mjackson

modules/Broadcast.js

@@ -1,6 +1,9 @@
 import React from "react";
 import PropTypes from "prop-types";
 import invariant from "invariant";
+import createDeprecationWarning from "./createDeprecationWarning";
+
+const deprecationWarning = createDeprecationWarning();
 
 function createBroadcast(initialValue) {
   let currentValue = initialValue;
@@ -68,6 +71,13 @@ class Broadcast extends React.Component {
     };
   }
 
+  componentWillMount() {
+    deprecationWarning(
+      "<Broadcast> is deprecated and will be removed in the next major release. " +
+        "Please use createBroadcast instead. See https://goo.gl/QAF37J for more info."
+    );
+  }
+
   componentWillReceiveProps(nextProps) {
     invariant(
       this.props.channel === nextProps.channel,

modules/Subscriber.js

@@ -1,6 +1,9 @@
 import React from "react";
 import PropTypes from "prop-types";
 import invariant from "invariant";
+import createDeprecationWarning from "./createDeprecationWarning";
+
+const deprecationWarning = createDeprecationWarning();
 
 /**
  * A <Subscriber> pulls the value for a channel off of context.broadcasts
@@ -40,6 +43,11 @@ class Subscriber extends React.Component {
   }
 
   componentWillMount() {
+    deprecationWarning(
+      "<Subscriber> is deprecated and will be removed in the next major release. " +
+        "Please use createBroadcast instead. See https://goo.gl/QAF37J for more info."
+    );
+
     const broadcast = this.getBroadcast();
 
     if (broadcast) {

modules/__tests__/createBroadcast-test.js

@@ -1,56 +1,64 @@
-import React from "react"
-import ReactDOM from "react-dom"
-import { Simulate } from "react-dom/test-utils"
-import createBroadcast from "../createBroadcast"
+import React from "react";
+import ReactDOM from "react-dom";
+import { Simulate } from "react-dom/test-utils";
+import createBroadcast from "../createBroadcast";
 
 describe("createBroadcast", () => {
   it("creates a Broadcast component", () => {
-    const { Broadcast } = createBroadcast()
-    expect(typeof Broadcast).toBe("function")
-  })
+    const { Broadcast } = createBroadcast();
+    expect(typeof Broadcast).toBe("function");
+  });
 
   it("creates a Subscriber component", () => {
-    const { Subscriber } = createBroadcast()
-    expect(typeof Subscriber).toBe("function")
-  })
-})
+    const { Subscriber } = createBroadcast();
+    expect(typeof Subscriber).toBe("function");
+  });
+});
+
+describe("A <Broadcast>", () => {
+  it("knows its default value", () => {
+    const defaultValue = "bubblegum";
+    const { Broadcast } = createBroadcast(defaultValue);
+    expect(defaultValue).toEqual(Broadcast.defaultValue);
+  });
+});
 
 describe("A <Subscriber>", () => {
-  let node
+  let node;
   beforeEach(() => {
-    node = document.createElement("div")
-  })
+    node = document.createElement("div");
+  });
 
   it("gets the initial broadcast value on the initial render", done => {
-    const initialValue = "cupcakes"
-    const { Broadcast, Subscriber } = createBroadcast(initialValue)
+    const defaultValue = "cupcakes";
+    const { Broadcast, Subscriber } = createBroadcast(defaultValue);
 
-    let actualValue
+    let actualValue;
 
     ReactDOM.render(
       <Broadcast>
         <Subscriber
           children={value => {
-            actualValue = value
-            return null
+            actualValue = value;
+            return null;
           }}
         />
       </Broadcast>,
       node,
       () => {
-        expect(actualValue).toBe(initialValue)
-        done()
+        expect(actualValue).toBe(defaultValue);
+        done();
       }
-    )
-  })
+    );
+  });
 
   it("gets the updated broadcast value as it changes", done => {
-    const { Broadcast, Subscriber } = createBroadcast("cupcakes")
+    const { Broadcast, Subscriber } = createBroadcast("cupcakes");
 
     class Parent extends React.Component {
       state = {
-        value: Broadcast.initialValue
-      }
+        value: Broadcast.defaultValue
+      };
 
       render() {
         return (
@@ -61,40 +69,66 @@ describe("A <Subscriber>", () => {
             />
             <Child />
           </Broadcast>
-        )
+        );
       }
     }
 
-    let childDidRender = false
+    let childDidRender = false;
 
     class Child extends React.Component {
-      // Make sure we can bypass a sCU=false!
+      // Make sure we can bypass sCU=false!
       shouldComponentUpdate() {
-        return false
+        return false;
       }
 
       render() {
         return (
           <Subscriber
             children={value => {
               if (childDidRender) {
-                expect(value).toBe("bubblegum")
-                done()
+                expect(value).toBe("bubblegum");
+                done();
               } else {
-                expect(value).toBe(Broadcast.initialValue)
+                expect(value).toBe(Broadcast.defaultValue);
               }
 
-              childDidRender = true
+              childDidRender = true;
 
-              return null
+              return null;
             }}
           />
-        )
+        );
       }
     }
 
     ReactDOM.render(<Parent />, node, function() {
-      Simulate.click(this.button)
-    })
-  })
-})
+      Simulate.click(this.button);
+    });
+  });
+
+  describe("under a <Broadcast> with a value different from the default", () => {
+    it("gets the broadcast value on the initial render", () => {
+      const defaultValue = "bubblegum";
+      const { Broadcast, Subscriber } = createBroadcast(defaultValue);
+
+      const node = document.createElement("div");
+
+      let actualValue;
+
+      ReactDOM.render(
+        <Broadcast value="cupcakes">
+          <Subscriber
+            children={value => {
+              actualValue = value;
+              return null;
+            }}
+          />
+        </Broadcast>,
+        node,
+        () => {
+          expect(actualValue).toEqual("cupcakes");
+        }
+      );
+    });
+  });
+});