Don't throw if hypothesisConfig() isn't a function

src/annotator/config/settings.js

@@ -84,14 +84,9 @@ function query(url) {
  *
  * If there's no window.hypothesisConfig() function then return {}.
  *
- * If there is a window.hypothesisConfig but it isn't a function then throw an
- * error.
- *
  * @param {Window} window_ - The window to search for a hypothesisConfig() function
  * @return {Object} - Any config settings returned by hypothesisConfig()
  *
- * @throws {TypeError} - If window.hypothesisConfig() isn't a function
- *
  */
 function configFuncSettingsFrom(window_) {
   if (!window_.hasOwnProperty('hypothesisConfig')) {
@@ -100,7 +95,8 @@ function configFuncSettingsFrom(window_) {
 
   if (typeof window_.hypothesisConfig !== 'function') {
     var docs = 'https://h.readthedocs.io/projects/client/en/latest/publishers/config/#window.hypothesisConfig';
-    throw new TypeError('hypothesisConfig must be a function, see: ' + docs);
+    console.warn('hypothesisConfig must be a function, see: ' + docs);
+    return {};
   }
 
   return window_.hypothesisConfig();

src/annotator/config/test/index-test.js

@@ -136,14 +136,6 @@ describe('annotator.config', function() {
     });
   });
 
-  context('when configFuncSettingsFrom() throws an error', function() {
-    it('throws the same error', function() {
-      fakeSettings.configFuncSettingsFrom.throws(new TypeError());
-
-      assert.throws(function() { configFrom(fakeWindow()); }, TypeError);
-    });
-  });
-
   describe('showHighlights', function() {
     [
       {

src/annotator/config/test/settings-test.js

@@ -2,7 +2,14 @@
 
 var settings = require('../settings');
 
+var sandbox = sinon.sandbox.create();
+
 describe('annotation.config.settings', function() {
+
+  afterEach('reset the sandbox', function() {
+    sandbox.restore();
+  });
+
   describe('#app', function() {
     function appendLinkToDocument(href) {
       var link = document.createElement('link');
@@ -197,13 +204,25 @@ describe('annotation.config.settings', function() {
     });
 
     context("when window.hypothesisConfig() isn't a function", function() {
-      it('throws an error', function() {
-        var fakeWindow = { hypothesisConfig: 42 };
+      beforeEach('stub console.warn()', function() {
+        sandbox.stub(console, 'warn');
+      });
 
-        assert.throws(
-          function() { settings.configFuncSettingsFrom(fakeWindow); },
-          TypeError
-        );
+      function fakeWindow() {
+        return {hypothesisConfig: 42};
+      }
+
+      it('returns {}', function() {
+        assert.deepEqual(settings.configFuncSettingsFrom(fakeWindow()), {});
+      });
+
+      it('logs a warning', function() {
+        settings.configFuncSettingsFrom(fakeWindow());
+
+        assert.calledOnce(console.warn);
+        assert.isTrue(console.warn.firstCall.args[0].startsWith(
+          'hypothesisConfig must be a function'
+        ));
       });
     });