Fix bug where exceptions were silently swallowed with synchronous render

fixes #678, #1116, #1127, and #1164. Closes #689

CHANGELOG.md

@@ -1,6 +1,15 @@
 Changelog
 =========
 
+3.1.6 (unreleased)
+------------------
+
+* Fix bug where exceptions were silently swallowed with synchronous render.
+  Fixes [#678](https://github.com/mozilla/nunjucks/issues/678),
+  [#1116](https://github.com/mozilla/nunjucks/issues/1116),
+  [#1127](https://github.com/mozilla/nunjucks/issues/1127), and
+  [#1164](https://github.com/mozilla/nunjucks/issues/1164)
+
 3.1.5 (Dec 13 2018)
 -------------------
 

nunjucks/src/environment.js

@@ -468,7 +468,11 @@ class Template extends Obj {
     this.rootRenderFunc(this.env, context, frame, globalRuntime, (err, res) => {
       if (didError) {
         // prevent multiple calls to cb
-        return;
+        if (cb) {
+          return;
+        } else {
+          throw err;
+        }
       }
       if (err) {
         err = lib._prettifyError(this.path, this.env.opts.dev, err);

tests/compiler.js

@@ -795,6 +795,14 @@
     });
 
     if (!isSlim) {
+      it('should throw exceptions when called synchronously', function() {
+        var tmpl = new Template('{% from "doesnotexist" import foo %}');
+        function templateRender() {
+          tmpl.render();
+        }
+        expect(templateRender).to.throwException(/template not found: doesnotexist/);
+      });
+
       it('should include error line in raised TemplateError', function(done) {
         var tmplStr = [
           '{% set items = ["a", "b",, "c"] %}',