Improve exception handling

packages/blaze/exceptions.js

@@ -1,4 +1,5 @@
 var debugFunc;
+var customFn;
 
 // We call into user code in many places, and it's nice to catch exceptions
 // propagated from user code immediately so that the whole system doesn't just
@@ -22,12 +23,26 @@ var debugFunc;
 // useful in unit tests that test error messages.
 Blaze._throwNextException = false;
 
+/**
+ * Allows to set a custom exceptions handler.
+ * @param fn {function} the function where exceptions will be piped
+ */
+Blaze.setExceptionHandler = function (fn) {
+  customFn = fn;
+};
+
 Blaze._reportException = function (e, msg) {
   if (Blaze._throwNextException) {
     Blaze._throwNextException = false;
     throw e;
   }
 
+  // if we have a custom exception handler we pipe the exception
+  // directly into it and omit the Meteor._debug handler here
+  if (customFn) {
+    return customFn(msg, e)
+  }
+
   if (! debugFunc)
     // adapted from Tracker
     debugFunc = function () {
@@ -43,14 +58,19 @@ Blaze._reportException = function (e, msg) {
 };
 
 Blaze._wrapCatchingExceptions = function (f, where) {
-  if (typeof f !== 'function')
+  if (typeof f !== 'function') {
     return f;
+  }
 
   return function () {
     try {
       return f.apply(this, arguments);
     } catch (e) {
-      Blaze._reportException(e, 'Exception in ' + where + ':');
+      if (Meteor.isPackageTest) {
+        throw e;
+      } else {
+        Blaze._reportException(e, `Exception in ${where}:`);
+      }
     }
   };
 };

packages/blaze/lookup.js

@@ -24,7 +24,7 @@ var bindIfIsFunction = function (x, target) {
 var bindDataContext = function (x) {
   if (typeof x === 'function') {
     return function () {
-      var data = Blaze.getData();
+      let data = Blaze.getData();
       if (data == null)
         data = {};
       return x.apply(data, arguments);
@@ -36,40 +36,30 @@ var bindDataContext = function (x) {
 Blaze._OLDSTYLE_HELPER = {};
 
 Blaze._getTemplateHelper = function (template, name, tmplInstanceFunc) {
-  // XXX COMPAT WITH 0.9.3
-  var isKnownOldStyleHelper = false;
-
   if (template.__helpers.has(name)) {
-    var helper = template.__helpers.get(name);
+    let helper = template.__helpers.get(name);
     if (helper === Blaze._OLDSTYLE_HELPER) {
-      isKnownOldStyleHelper = true;
-    } else if (helper != null) {
-      return wrapHelper(bindDataContext(helper), tmplInstanceFunc);
+      throw new Meteor.Error("not-suported", "We removed support for old style templates");
+    } else if (helper !== null) {
+      return wrapHelper(
+        bindDataContext(helper),
+        tmplInstanceFunc,
+        `${template.viewName} ${name}`
+      );
     } else {
       return null;
     }
   }
 
-  // old-style helper
+  // all unkown-old style helpers
   if (name in template) {
-    // Only warn once per helper
-    if (! isKnownOldStyleHelper) {
-      template.__helpers.set(name, Blaze._OLDSTYLE_HELPER);
-      if (! template._NOWARN_OLDSTYLE_HELPERS) {
-        Blaze._warn('Assigning helper with `' + template.viewName + '.' +
-                    name + ' = ...` is deprecated.  Use `' + template.viewName +
-                    '.helpers(...)` instead.');
-      }
-    }
-    if (template[name] != null) {
-      return wrapHelper(bindDataContext(template[name]), tmplInstanceFunc);
-    }
+    throw new Meteor.Error("not-suported", "We removed support for old style templates");
   }
 
   return null;
 };
 
-var wrapHelper = function (f, templateFunc) {
+var wrapHelper = function (f, templateFunc, name) {
   if (typeof f !== "function") {
     return f;
   }
@@ -79,7 +69,7 @@ var wrapHelper = function (f, templateFunc) {
     var args = arguments;
 
     return Blaze.Template._withTemplateInstanceFunc(templateFunc, function () {
-      return Blaze._wrapCatchingExceptions(f, 'template helper').apply(self, args);
+      return Blaze._wrapCatchingExceptions(f, name).apply(self, args);
     });
   };
 };
@@ -134,7 +124,10 @@ Blaze._getTemplate = function (name, templateInstance) {
 
 Blaze._getGlobalHelper = function (name, templateInstance) {
   if (Blaze._globalHelpers[name] != null) {
-    return wrapHelper(bindDataContext(Blaze._globalHelpers[name]), templateInstance);
+    return wrapHelper(
+      bindDataContext(Blaze._globalHelpers[name]),
+      templateInstance,
+      `global helper ${name}`);
   }
   return null;
 };

packages/spacebars-tests/template_tests.js

@@ -3782,20 +3782,26 @@ Tinytest.add(
 
     // Test old-style helper
     tmpl.foo = 'hello';
-    var div = renderToDiv(tmpl);
-    test.equal(canonicalizeHtml(div.innerHTML), 'hello');
+    test.throws(function () {
+      var div = renderToDiv(tmpl);
+      test.equal(canonicalizeHtml(div.innerHTML), 'hello');
+    }, /We removed support for old style templates/)
 
     // Test that replacing a helper still works (i.e. we don't cache them).
     // We can change this behavior if we need to, but it is more breaking
     // to do so.  It breaks some unit tests, for example.
     tmpl.foo = 'world';
-    var div = renderToDiv(tmpl);
-    test.equal(canonicalizeHtml(div.innerHTML), 'world');
+
+    test.throws(function () {
+      var div = renderToDiv(tmpl);
+      test.equal(canonicalizeHtml(div.innerHTML), 'world');
+    }, /We removed support for old style templates/)
 
     // Test that you can delete an old-style helper with `delete`.
     // As with the previous case, we can break this functionality, but
     // we should do it intentionally.
     delete tmpl.foo;
+
     var div = renderToDiv(tmpl);
     test.equal(canonicalizeHtml(div.innerHTML), '');
   }

packages/spacebars-tests/templating_tests.js

@@ -468,7 +468,7 @@ Tinytest.add("spacebars-tests - templating_tests - template arg", function (test
 Tinytest.add("spacebars-tests - templating_tests - helpers", function (test) {
   var tmpl = Template.test_template_helpers_a;
 
-  tmpl._NOWARN_OLDSTYLE_HELPERS = true;
+  // tmpl._NOWARN_OLDSTYLE_HELPERS = true;
   tmpl.foo = 'z';
   tmpl.helpers({bar: 'b'});
   // helpers(...) takes precendence of assigned helper