Extract a new configFuncSettingsFrom() function

Extract some code for reading config settings from a
window.hypothesisConfig() function out of
annotator.config.config#configFrom() and into a new, separate function
annotator.config.settings#configFuncSettingsFrom().

This function can now be unit-tested separately and the long
configFrom() function gets a bit shorter.

src/annotator/config/index.js

@@ -3,8 +3,6 @@
 var settings = require('./settings');
 var sharedSettings = require('../../shared/settings');
 
-var docs = 'https://h.readthedocs.io/en/latest/embedding.html';
-
 /**
  * Reads the Hypothesis configuration from the environment.
  *
@@ -53,14 +51,7 @@ function configFrom(window_) {
       err);
   }
 
-  // Parse config from `window.hypothesisConfig` function
-  if (window_.hasOwnProperty('hypothesisConfig')) {
-    if (typeof window_.hypothesisConfig === 'function') {
-      Object.assign(config, window_.hypothesisConfig());
-    } else {
-      throw new TypeError('hypothesisConfig must be a function, see: ' + docs);
-    }
-  }
+  Object.assign(config, settings.configFuncSettingsFrom(window_));
 
   // Convert legacy keys/values in config to corresponding current
   // configuration.

src/annotator/config/settings.js

@@ -41,7 +41,44 @@ function query(url) {
   return null;
 }
 
+/**
+ * Return an object containing config settings from window.hypothesisConfig().
+ *
+ * Return an object containing config settings returned by the
+ * window.hypothesisConfig() function provided by the host page:
+ *
+ *   {
+ *     fooSetting: 'fooValue',
+ *     barSetting: 'barValue',
+ *     ...
+ *   }
+ *
+ * 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')) {
+    return {};
+  }
+
+  if (typeof window_.hypothesisConfig !== 'function') {
+    var docs = 'https://h.readthedocs.io/en/latest/embedding.html';
+    throw new TypeError('hypothesisConfig must be a function, see: ' + docs);
+  }
+
+  return window_.hypothesisConfig();
+}
+
 module.exports = {
   annotations: annotations,
   query: query,
+  configFuncSettingsFrom: configFuncSettingsFrom,
 };

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

@@ -37,6 +37,7 @@ describe('annotator.config', function() {
   beforeEach('reset fakeSettings', function() {
     fakeSettings.annotations = sinon.stub();
     fakeSettings.query = sinon.stub();
+    fakeSettings.configFuncSettingsFrom = sinon.stub().returns({});
   });
 
   afterEach('reset the sandbox', function() {
@@ -109,51 +110,42 @@ describe('annotator.config', function() {
     });
   });
 
-  context("when there's a window.hypothesisConfig() function", function() {
-    it('reads arbitrary settings from hypothesisConfig() into config', function() {
+  it('gets config settings from window.hypothesisConfig()', function() {
     var window_ = fakeWindow();
-      window_.hypothesisConfig = sinon.stub().returns({foo: 'bar'});
 
-      var config = configFrom(window_);
+    configFrom(window_);
+
+    assert.calledOnce(fakeSettings.configFuncSettingsFrom);
+    assert.calledWithExactly(fakeSettings.configFuncSettingsFrom, window_);
+  });
+
+  context('when configFuncSettingsFrom() returns an object', function() {
+    it('reads arbitrary settings from configFuncSettingsFrom() into config', function() {
+      fakeSettings.configFuncSettingsFrom.returns({foo: 'bar'});
+
+      var config = configFrom(fakeWindow());
 
       assert.equal(config.foo, 'bar');
     });
 
     specify('hypothesisConfig() settings override js-hypothesis-config ones', function() {
-      var window_ = fakeWindow();
-      window_.hypothesisConfig = sinon.stub().returns({
+      fakeSettings.configFuncSettingsFrom.returns({
         foo: 'fooFromHypothesisConfigFunc'});
       fakeSharedSettings.jsonConfigsFrom.returns({
         foo: 'fooFromJSHypothesisConfigObj',
       });
 
-      var config = configFrom(window_);
+      var config = configFrom(fakeWindow());
 
       assert.equal(config.foo, 'fooFromHypothesisConfigFunc');
     });
-
-    context('if hypothesisConfig() returns a non-object value', function() {
-      it("doesn't add anything into the config", function() {
-        var window_ = fakeWindow();
-        window_.hypothesisConfig = sinon.stub().returns(42);
-
-        var config = configFrom(window_);
-
-        delete config.app; // We don't care about config.app for this test.
-        assert.deepEqual({}, config);
-      });
-    });
   });
 
-  context("when window.hypothesisConfig() isn't a function", function() {
-    it('throws a TypeError', function() {
-      var window_ = fakeWindow();
-      window_.hypothesisConfig = 'notAFunction';
+  context('when configFuncSettingsFrom() throws an error', function() {
+    it('throws the same error', function() {
+      fakeSettings.configFuncSettingsFrom.throws(new TypeError());
 
-      assert.throws(
-        function() { configFrom(window_); }, TypeError,
-        'hypothesisConfig must be a function, see: https://h.readthedocs.io/en/latest/embedding.html'
-      );
+      assert.throws(function() { configFrom(fakeWindow()); }, TypeError);
     });
   });
 

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

@@ -111,4 +111,35 @@ describe('annotation.config.settings', function() {
       });
     });
   });
+
+  describe('#configFuncSettingsFrom', function() {
+    context("when there's no window.hypothesisConfig() function", function() {
+      it('returns {}', function() {
+        var fakeWindow = {};
+
+        assert.deepEqual(settings.configFuncSettingsFrom(fakeWindow), {});
+      });
+    });
+
+    context("when window.hypothesisConfig() isn't a function", function() {
+      it('throws an error', function() {
+        var fakeWindow = { hypothesisConfig: 42 };
+
+        assert.throws(
+          function() { settings.configFuncSettingsFrom(fakeWindow); },
+          TypeError
+        );
+      });
+    });
+
+    context('when window.hypothesisConfig() is a function', function() {
+      it('returns whatever window.hypothesisConfig() returns', function () {
+        // It just blindly returns whatever hypothesisConfig() returns
+        // (even if it's not an object).
+        var fakeWindow = { hypothesisConfig: sinon.stub().returns(42) };
+
+        assert.equal(settings.configFuncSettingsFrom(fakeWindow), 42);
+      });
+    });
+  });
 });