feature: rich info error

index.js

@@ -47,7 +47,7 @@ var _engine = {
             .then(() => this.parse(html))
             .then(tpl => this.render(tpl, ctx, opts))
             .catch(e => {
-                if (e instanceof Errors.RenderBreak) {
+                if (e instanceof Errors.RenderBreakError) {
                     return e.html;
                 }
                 throw e;
@@ -145,7 +145,7 @@ factory.evalValue = Syntax.evalValue;
 factory.Types = {
     ParseError: Errors.ParseError,
     TokenizationEroor: Errors.TokenizationError,
-    RenderBreak: Errors.RenderBreak,
+    RenderBreakError: Errors.RenderBreakError,
     AssertionError: Errors.AssertionError
 };
 

src/parser.js

@@ -52,16 +52,18 @@ module.exports = function(Tag, Filter) {
 
     function parseToken(token, tokens) {
         try {
-            switch (token.type) {
-                case 'tag':
-                    return parseTag(token, tokens);
-                case 'output':
-                    return parseOutput(token.value);
-                case 'html':
-                    return token;
+            var tpl = null;
+            if (token.type === 'tag') {
+                tpl = parseTag(token, tokens);
+            } else if (token.type === 'output') {
+                tpl = parseOutput(token.value);
+            } else { // token.type === 'html'
+                tpl = token;
             }
+            tpl.token = token;
+            return tpl;
         } catch (e) {
-            throw new ParseError(e.message, token.input, token.line, e);
+            throw new ParseError(e, token);
         }
     }
 
@@ -78,7 +80,7 @@ module.exports = function(Tag, Filter) {
         str = str.substr(match.index + match[0].length);
 
         var filters = [];
-        while(match = lexical.filter.exec(str)){
+        while (match = lexical.filter.exec(str)) {
             filters.push([match[0].trim()]);
         }
 
@@ -95,6 +97,9 @@ module.exports = function(Tag, Filter) {
     }
 
     return {
-        parse, parseTag, parseStream, parseOutput
+        parse,
+        parseTag,
+        parseStream,
+        parseOutput
     };
 };

src/render.js

@@ -1,9 +1,9 @@
 const Syntax = require('./syntax.js');
 const Promise = require('any-promise');
 const mapSeries = require('./util/promise.js').mapSeries;
-const RenderBreak = require('./util/error.js').RenderBreak;
+const RenderBreakError = require('./util/error.js').RenderBreakError;
+const RenderError = require('./util/error.js').RenderError;
 const assert = require('./util/assert.js');
-const _ = require('./util/underscore.js');
 
 var render = {
 
@@ -15,10 +15,11 @@ var render = {
             return renderTemplate.call(this, tpl)
                 .then(partial => html += partial)
                 .catch(e => {
-                    if(e instanceof RenderBreak){
+                    if(e instanceof RenderBreakError){
                         e.resolvedHTML = html;                
+                        throw e;
                     }
-                    throw e;
+                    throw new RenderError(e, tpl);
                 });
         }).then(() => html);
 
@@ -27,7 +28,8 @@ var render = {
                 return this.renderTag(template, scope)
                     .then(partial => partial === undefined ? '' : partial);
             } else if (template.type === 'output') {
-                return Promise.resolve(this.evalOutput(template, scope))
+                return Promise.resolve()
+                    .then(() => this.evalOutput(template, scope))
                     .then(partial => partial === undefined ? '' : stringify(partial));
             } else { // template.type === 'html'
                 return Promise.resolve(template.value);
@@ -37,10 +39,10 @@ var render = {
 
     renderTag: function(template, scope) {
         if (template.name === 'continue') {
-            return Promise.reject(new RenderBreak('continue'));
+            return Promise.reject(new RenderBreakError('continue'));
         }
         if (template.name === 'break') {
-            return Promise.reject(new RenderBreak('break'));
+            return Promise.reject(new RenderBreakError('break'));
         }
         return template.render(scope);
     },
@@ -53,7 +55,7 @@ var render = {
                 if (scope.get('liquid.strict_filters')) {
                     throw filter.error;
                 } else { 
-                    val = ''
+                    val = '';
                     return true;
                 }
             }

src/tag.js

@@ -1,10 +1,12 @@
 const lexical = require('./lexical.js');
+const _ = require('./util/underscore.js');
 const Promise = require('any-promise');
 const Syntax = require('./syntax.js');
 const assert = require('./util/assert.js');
 
 function hash(markup, scope) {
-    var obj = {}, match;
+    var obj = {},
+        match;
     lexical.hashCapture.lastIndex = 0;
     while (match = lexical.hashCapture.exec(markup)) {
         var k = match[1],
@@ -20,9 +22,22 @@ module.exports = function() {
     var _tagInstance = {
         render: function(scope) {
             var obj = hash(this.token.args, scope);
-            return this.tagImpl.render && this.tagImpl.render(scope, obj) || Promise.resolve('');
+            var impl = this.tagImpl;
+            if (typeof impl.render !== 'function') {
+                return Promise.resolve('');
+            }
+            return Promise.resolve()
+                .then(() => typeof impl.render === 'function' ?
+                    impl.render(scope, obj) : '')
+                .catch(function(e) {
+                    if (_.isError(e)) {
+                        throw e;
+                    }
+                    var msg = `Please reject with an Error in ${impl.render}, got ${e}`;
+                    throw new Error(msg);
+                });
         },
-        parse: function(token, tokens){
+        parse: function(token, tokens) {
             this.type = 'tag';
             this.token = token;
             this.name = token.name;
@@ -30,7 +45,7 @@ module.exports = function() {
             var tagImpl = tagImpls[this.name];
             assert(tagImpl, `tag ${this.name} not found`);
             this.tagImpl = Object.create(tagImpl);
-            if(this.tagImpl.parse){
+            if (this.tagImpl.parse) {
                 this.tagImpl.parse(token, tokens);
             }
         }
@@ -51,6 +66,8 @@ module.exports = function() {
     }
 
     return {
-        construct, register, clear
+        construct,
+        register,
+        clear
     };
 };

src/tokenizer.js

@@ -4,9 +4,9 @@ const _ = require('./util/underscore.js');
 const assert = require('../src/util/assert.js');
 
 function parse(html) {
-    var tokens = [];
-    assert(_.isString(html), new TokenizationError('illegal input type'));
+    assert(_.isString(html), 'illegal input type');
 
+    var tokens = [];
     var syntax = /({%(.*?)%})|({{(.*?)}})/g;
     var result, htmlFragment, token;
     var lastMatchEnd = 0, lastMatchBegin = -1, parsedLinesCount = 0;
@@ -27,8 +27,7 @@ function parse(html) {
 
             var match = token.value.match(lexical.tagLine);
             if (!match) {
-                throw new TokenizationError(`illegal tag: ${token.raw}`,
-                    token.input, token.line);
+                throw new TokenizationError(`illegal tag syntax`, token);
             }
             token.name = match[1];
             token.args = match[2];
@@ -36,8 +35,7 @@ function parse(html) {
             tokens.push(token);
         }
         // output
-        else {
-            token = factory('output', 3, result);
+        else { token = factory('output', 3, result);
             tokens.push(token);
         }
         lastMatchEnd = syntax.lastIndex;
@@ -60,17 +58,10 @@ function parse(html) {
             raw: match[offset],
             value: match[offset + 1].trim(),
             line: getLineNum(match),
-            input: getLineContent(match)
+            input: html
         };
     }
 
-    function getLineContent(match) {
-        var idx1 = match.input.lastIndexOf('\n', match.index);
-        var idx2 = match.input.indexOf('\n', match.index);
-        if (idx2 === -1) idx2 = match.input.length;
-        return match.input.slice(idx1 + 1, idx2);
-    }
-
     function getLineNum(match) {
         var lines = match.input.slice(lastMatchBegin + 1, match.index).split('\n');
         parsedLinesCount += lines.length - 1;

src/util/error.js

@@ -1,46 +1,58 @@
-function TokenizationError(message, input, line) {
-    if(Error.captureStackTrace){
+const _ = require('./underscore.js');
+
+function TokenizationError(message, token) {
+    if (Error.captureStackTrace) {
         Error.captureStackTrace(this, this.constructor);
     }
     this.name = this.constructor.name;
 
-    this.message = message;
-    this.input = input;
-    this.line = line;
+    this.input = token.input;
+    this.line = token.line;
+
+    var context = mkContext(token.input, token.line);
+    this.message = message + '\n' + context;
 }
 TokenizationError.prototype = Object.create(Error.prototype);
 TokenizationError.prototype.constructor = TokenizationError;
 
-function ParseError(message, input, line, e) {
-    if(Error.captureStackTrace){
-        Error.captureStackTrace(this, this.constructor);
-    } else{
-        this.stack = "";
-    }
-    this.stack += (this.stack ? "\nFrom " : "From ") + e.stack;
-
+function ParseError(e, token) {
     this.name = this.constructor.name;
-    this.originalError = e;
+    this.stack = e.stack;
 
-    this.message = message;
-    this.input = input;
-    this.line = line;
+    this.input = token.input;
+    this.line = token.line;
+
+    var context = mkContext(token.input, token.line);
+    this.message = e.message + '\n' + context;
 }
 ParseError.prototype = Object.create(Error.prototype);
 ParseError.prototype.constructor = ParseError;
 
-function RenderBreak(message){
-    if(Error.captureStackTrace){
+function RenderError(e, tpl) {
+    this.name = this.constructor.name;
+    this.stack = e.stack;
+
+    this.input = tpl.token.input;
+    this.line = tpl.token.line;
+
+    var context = mkContext(tpl.token.input, tpl.token.line);
+    this.message = e.message + '\n' + context;
+}
+RenderError.prototype = Object.create(Error.prototype);
+RenderError.prototype.constructor = RenderError;
+
+function RenderBreakError(message) {
+    if (Error.captureStackTrace) {
         Error.captureStackTrace(this, this.constructor);
     }
     this.name = this.constructor.name;
-    this.message = message;
+    this.message = message || '';
 }
-RenderBreak.prototype = Object.create(Error.prototype);
-RenderBreak.prototype.constructor = RenderBreak;
+RenderBreakError.prototype = Object.create(Error.prototype);
+RenderBreakError.prototype.constructor = RenderBreakError;
 
-function AssertionError(message){
-    if(Error.captureStackTrace){
+function AssertionError(message) {
+    if (Error.captureStackTrace) {
         Error.captureStackTrace(this, this.constructor);
     }
     this.name = this.constructor.name;
@@ -49,6 +61,35 @@ function AssertionError(message){
 AssertionError.prototype = Object.create(Error.prototype);
 AssertionError.prototype.constructor = AssertionError;
 
+function mkContext(input, line) {
+    var lines = input.split('\n');
+    var begin = Math.max(line - 2, 1);
+    var end = Math.min(line + 3, lines.length);
+
+    var context = _
+        .range(begin, end + 1)
+        .map(l => [
+            (l === line) ? '>> ' : '   ',
+            align(l, end),
+            '| ',
+            lines[l - 1]
+        ].join(''))
+        .join('\n');
+
+    return context;
+}
+
+function align(n, max) {
+    var length = (max + '').length;
+    var str = n + '';
+    var blank = Array(length - str.length).join(' ');
+    return blank + str;
+}
+
 module.exports = {
-    TokenizationError, ParseError, RenderBreak, AssertionError
+    TokenizationError,
+    ParseError,
+    RenderBreakError,
+    AssertionError,
+    RenderError
 };

src/util/underscore.js

@@ -7,6 +7,13 @@ function isString(value) {
     return value instanceof String || typeof value === 'string';
 }
 
+function isError(value) {
+    var signature = Object.prototype.toString.call(value);
+    // [object XXXError]
+    return signature.substr(-6, 5) === 'Error' ||
+        (typeof value.message == 'string' && typeof value.name == 'string');
+}
+
 /*
  * Iterates over own enumerable string keyed properties of an object and invokes iteratee for each property. 
  * The iteratee is invoked with three arguments: (value, key, object). 
@@ -88,9 +95,34 @@ function isObject(value) {
     return value !== null && typeof value === 'object';
 }
 
+/*
+ * A function to create flexibly-numbered lists of integers, 
+ * handy for each and map loops. start, if omitted, defaults to 0; step defaults to 1. 
+ * Returns a list of integers from start (inclusive) to stop (exclusive), 
+ * incremented (or decremented) by step, exclusive. 
+ * Note that ranges that stop before they start are considered to be zero-length instead of 
+ * negative — if you'd like a negative range, use a negative step.
+ */
+function range(start, stop, step) {
+    if (arguments.length === 1) {
+        stop = start;
+        start = 0;
+    }
+    step = step || 1;
+
+    var arr = [];
+    for (var i = start; i < stop; i += step) {
+        arr.push(i);
+    }
+    return arr;
+}
+
 exports.isString = isString;
 exports.isArray = isArray;
 exports.isObject = isObject;
+exports.isError = isError;
+
+exports.range = range;
 
 exports.forOwn = forOwn;
 exports.assign = assign;

tags/for.js

@@ -1,8 +1,7 @@
 const Liquid = require('..');
-const Promise = require('any-promise');
 const lexical = Liquid.lexical;
 const mapSeries = require('../src/util/promise.js').mapSeries;
-const RenderBreak = Liquid.Types.RenderBreak;
+const RenderBreakError = Liquid.Types.RenderBreakError;
 const assert = require('../src/util/assert.js');
 const re = new RegExp(`^(${lexical.identifier.source})\\s+in\\s+` +
     `(${lexical.value.source})` +
@@ -23,11 +22,11 @@ module.exports = function(liquid) {
             this.elseTemplates = [];
 
             var p, stream = liquid.parser.parseStream(remainTokens)
-                .on('start', x => p = this.templates)
-                .on('tag:else', token => p = this.elseTemplates)
-                .on('tag:endfor', token => stream.stop())
+                .on('start', () => p = this.templates)
+                .on('tag:else', () => p = this.elseTemplates)
+                .on('tag:endfor', () => stream.stop())
                 .on('template', tpl => p.push(tpl))
-                .on('end', x => {
+                .on('end', () => {
                     throw new Error(`tag ${tagToken.raw} not closed`);
                 });
 
@@ -71,7 +70,7 @@ module.exports = function(liquid) {
                     .renderTemplates(this.templates, scope)
                     .then(partial => html += partial)
                     .catch(e => {
-                        if (e instanceof RenderBreak) {
+                        if (e instanceof RenderBreakError) {
                             html += e.resolvedHTML;
                             if (e.message === 'continue') return;
                         }
@@ -79,7 +78,7 @@ module.exports = function(liquid) {
                     })
                     .then(() => scope.pop());
             }).catch((e) => {
-                if (e instanceof RenderBreak && e.message === 'break') {
+                if (e instanceof RenderBreakError && e.message === 'break') {
                     return;
                 }
                 throw e;

test/tag.js

@@ -41,12 +41,14 @@ describe('tag', function() {
         tag.register('foo', {
             render: spy
         });
-        tag.construct({
-            type: 'tag',
-            value: 'foo',
-            name: 'foo'
-        }, []).render(scope, {});
-        expect(spy).to.have.been.called;
+        return tag
+            .construct({
+                type: 'tag',
+                value: 'foo',
+                name: 'foo'
+            }, [])
+            .render(scope, {})
+            .then(() => expect(spy).to.have.been.called);
     });
 
     it('should call tag.render with resolved hash', function() {
@@ -61,11 +63,11 @@ describe('tag', function() {
             name: 'foo',
             args: 'aa:foo bb: arr[0] cc: 2.3'
         };
-        tag.construct(token, []).render(scope, {});
-        expect(spy).to.have.been.calledWithMatch(scope, {
-            aa: 'bar',
-            bb: 2,
-            cc: 2.3
-        });
+        return tag.construct(token, []).render(scope, {})
+            .then(() => expect(spy).to.have.been.calledWithMatch(scope, {
+                aa: 'bar',
+                bb: 2,
+                cc: 2.3
+            }));
     });
 });

test/tags/for.js

@@ -52,27 +52,30 @@ describe('tags/for', function() {
             .to.eventually.equal('12345');
     });
     it('should support for with break', function() {
-        src = '{% for i in (one..5) %}' +
+        var src = '{% for i in (one..5) %}' +
             '{% if i == 4 %}{% break %}{% endif %}' +
             '{{ i }}' +
             '{% endfor %}';
+        //return liquid.parseAndRender(src, ctx).catch(e => {
+            //console.log(e.stack);
+        //});
         return expect(liquid.parseAndRender(src, ctx))
             .to.eventually.equal('123');
     });
 
     it('should support for with limit', function() {
-        src = '{% for i in (1..5) limit:2 %}{{ i }}{% endfor %}';
+        var src = '{% for i in (1..5) limit:2 %}{{ i }}{% endfor %}';
         return expect(liquid.parseAndRender(src, ctx))
             .to.eventually.equal('12');
     });
     it('should support for with limit and offset', function() {
-        src = '{% for i in (1..10) limit:2 offset:5%}{{ i }}{% endfor %}';
+        var src = '{% for i in (1..10) limit:2 offset:5%}{{ i }}{% endfor %}';
         return expect(liquid.parseAndRender(src, ctx))
             .to.eventually.equal('67');
     });
 
     it('should support for reversed', function() {
-        src = '{% for i in (1..5) limit:2 reversed %}{{ i }}{% endfor %}';
+        var src = '{% for i in (1..5) limit:2 reversed %}{{ i }}{% endfor %}';
         return expect(liquid.parseAndRender(src, ctx))
             .to.eventually.equal('21');
     });

test/util/error.js

@@ -13,92 +13,310 @@ describe('error', function() {
 
     describe('TokenizationError', function() {
         it('should throw TokenizationError when tag illegal', function() {
-            return engine.parseAndRender('{% . a %}', {}).catch(function(err) {
-                expect(err.name).to.equal('TokenizationError');
-                expect(err.message).to.equal('illegal tag: {% . a %}');
-                expect(err.input).to.equal('{% . a %}');
-                expect(err.line).to.equal(1);
-            });
+            return expect(engine.parseAndRender('{% . a %}', {})).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('TokenizationError');
+                    expect(err.message).to.contain('illegal tag syntax');
+                });
         });
-        it('should throw TokenizationError when tag syntax illegal', function() {
-            return engine.parseAndRender('{% . a }', {}).catch(function(err) {
-                expect(err.name).to.equal('TokenizationError');
-                expect(err.message).to.equal('illegal tag: {% . a }');
-                expect(err.input).to.equal('{% . a }');
-                expect(err.line).to.equal(1);
-            });
+        it('should contain template content in err.message', function() {
+            var html = ['1st', '2nd', 'X{% . a %} Y', '4th'];
+            var message = [
+                'illegal tag syntax',
+                '   1| 1st',
+                '   2| 2nd',
+                '>> 3| X{% . a %} Y',
+                '   4| 4th'
+            ];
+            return expect(engine.parseAndRender(html.join('\n'))).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.message).to.equal(message.join('\n'));
+                    expect(err.name).to.equal('TokenizationError');
+                });
         });
-        it('should throw TokenizationError when filter syntax illegal', function() {
-            return engine.parseAndRender('{{ a|| }}', {}).catch(function(err) {
-                expect(err.name).to.equal('TokenizationError');
-                expect(err.message).to.equal('{{ a|| }');
-                expect(err.input).to.equal('{{ a|| }');
-                expect(err.line).to.equal(1);
+        it('should contain the whole template content in err.input', function() {
+            var html = 'bar\nfoo{% . a %}\nfoo';
+            return expect(engine.parseAndRender(html)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.input).to.equal(html);
+                });
+        });
+        it('should contain line number in err.line', function() {
+            return expect(engine.parseAndRender('1\n2\n{% . a %}\n4', {})).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('TokenizationError');
+                    expect(err.line).to.equal(3);
+                });
+        });
+        it('should contain stack in err.stack', function() {
+            return expect(engine.parseAndRender('{% . a %}')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.stack).to.contain('illegal tag syntax');
+                    expect(err.stack).to.contain('at Object.parse');
+                });
+        });
+        it('should contain file path in err.file', function() {
+            var html = '<html>\n<head>\n\n{% . a %}\n\n';
+            mock({
+                "/foo.html": html
             });
+            return expect(engine.renderFile('/foo.html')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    mock.restore();
+                    expect(err.name).to.equal('TokenizationError');
+                    expect(err.file).to.equal('/foo.html');
+                });
         });
     });
 
-    describe('TypeError', function() {
+    describe('RenderError', function() {
+        beforeEach(function() {
+            engine = require('../..')();
+            engine.registerTag('throwingTag', {
+                render: function() {
+                    throw new Error('intended render error');
+                }
+            });
+            engine.registerTag('rejectingTag', {
+                render: function() {
+                    return Promise.reject(new Error('intended render reject'));
+                }
+            });
+            engine.registerFilter('throwingFilter', () => {
+                throw new Error('throwed by filter');
+            });
+        });
+        it('should throw RenderError when tag throws', function() {
+            var src = '{%throwingTag%}';
+            return expect(engine.parseAndRender(src)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('RenderError');
+                    expect(err.message).to.contain('intended render error');
+                });
+        });
+        it('should throw RenderError when tag rejects', function() {
+            var src = '{%rejectingTag%}';
+            return expect(engine.parseAndRender(src)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('RenderError');
+                    expect(err.message).to.contain('intended render reject');
+                });
+        });
+        it('should throw RenderError when filter throws', function() {
+            var src = '{{1|throwingFilter}}';
+            return expect(engine.parseAndRender(src)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('RenderError');
+                    expect(err.message).to.contain('throwed by filter');
+                });
+        });
         it('should not throw when variable undefined by default', function() {
             return expect(engine.parseAndRender('X{{a}}Y')).to.eventually.equal('XY');
         });
-        it('should throw TypeError when variable not defined', function() {
+        it('should throw RenderError when variable not defined', function() {
             return expect(strictEngine.parseAndRender('{{a}}')).to.eventually
                 .be.rejected
-                .then(function(e){
-                    expect(e).to.have.property('name', 'TypeError');
-                    expect(e).to.have.property('message', 'undefined variable: a');
+                .then(function(e) {
+                    expect(e).to.have.property('name', 'RenderError');
+                    expect(e.message).to.contain('undefined variable: a');
                 });
         });
-        it('should throw TypeError when filter not defined', function() {
+        it('should throw RenderError when filter not defined', function() {
             return expect(strictEngine.parseAndRender('{{1 | a}}')).to.eventually
                 .be.rejected
-                .then(function(e){
-                    expect(e).to.have.property('name', 'TypeError');
-                    expect(e).to.have.property('message', 'undefined filter: a');
+                .then(function(e) {
+                    expect(e).to.have.property('name', 'RenderError');
+                    expect(e.message).to.contain('undefined filter: a');
+                });
+        });
+        it('should contain template content in err.message', function() {
+            var html = ['1st', '2nd', '3rd', 'X{%throwingTag%} Y', '5th', '6th', '7th'];
+            var message = [
+                'intended render error',
+                '   2| 2nd',
+                '   3| 3rd',
+                '>> 4| X{%throwingTag%} Y',
+                '   5| 5th',
+                '   6| 6th',
+                '   7| 7th'
+            ];
+            return expect(engine.parseAndRender(html.join('\n'))).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.message).to.equal(message.join('\n'));
+                    expect(err.name).to.equal('RenderError');
+                });
+        });
+        it('should contain the whole template content in err.input', function() {
+            var html = 'bar\nfoo{%throwingTag%}\nfoo';
+            return expect(engine.parseAndRender(html)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.input).to.equal(html);
+                    expect(err.name).to.equal('RenderError');
+                });
+        });
+        it('should contain line number in err.line', function() {
+            var src = '1\n2\n{{1|throwingFilter}}\n4';
+            return expect(engine.parseAndRender(src)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.line).to.equal(3);
+                    expect(err.name).to.equal('RenderError');
+                });
+        });
+        it('should contain stack in err.stack', function() {
+            return expect(engine.parseAndRender('{%rejectingTag%}')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.stack).to.contain('intended render reject');
+                    expect(err.stack).to.contain('at Object.engine.registerTag.render');
+                });
+        });
+
+        it('should contain file path in err.file', function() {
+            var html = '<html>\n<head>\n\n{% throwingTag %}\n\n';
+            mock({
+                "/foo.html": html
+            });
+            return expect(engine.renderFile('/foo.html')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    mock.restore();
+                    expect(err.name).to.equal('RenderError');
+                    expect(err.file).to.equal('/foo.html');
                 });
         });
     });
 
     describe('ParseError', function() {
-        it('should throw correct error info', function() {
-            var src = '{%if true%}\naaa{%endif%}\n{% -a %}\n3';
-            return engine.parseAndRender(src).catch(function(err) {
-                expect(err.name).to.equal('ParseError');
-                expect(err.input).to.equal('{% -a %}');
-                expect(err.line).to.equal(3)
-                expect(err.stack).to.contain('From AssertionError: tag -a not found');
+        beforeEach(function() {
+            engine = require('../..')();
+            engine.registerTag('throwsOnParse', {
+                parse: function() {
+                    throw new Error('intended parse error');
+                }
             });
         });
-        it('should throw correct error info for files', function() {
-            mock({
-                "/foo.html": '<html>\n<head>\n\n{% raw %}\n\n'
-            });
-            return engine.renderFile('/foo.html').catch(function(err) {
-                mock.restore();
-                expect(err.name).to.equal('ParseError');
-                expect(err.input).to.equal('{% raw %}');
-                expect(err.line).to.equal(4);
-                expect(err.file).to.equal('/foo.html');
-            });
+        it('should throw ParseError when tag not closed', function() {
+            return expect(engine.parseAndRender('{% if %}')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('ParseError');
+                    expect(err.message).to.contain('tag {% if %} not closed');
+                });
+        });
+        it('should throw ParseError when tag parse throws', function() {
+            var src = '{%throwsOnParse%}';
+            return expect(engine.parseAndRender(src)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('ParseError');
+                    expect(err.message).to.contain('intended parse error');
+                });
+        });
+        it('should throw ParseError when tag not found', function() {
+            var src = '{%if true%}\naaa{%endif%}\n{% -a %}\n3';
+            return expect(engine.parseAndRender(src)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('ParseError');
+                    expect(err.message).to.contain('tag -a not found');
+                });
         });
 
         it('should throw ParseError when tag not exist', function() {
-            return engine.parseAndRender('{% a %}').catch(function(err) {
-                expect(err.name).to.equal('ParseError');
-                expect(err.message).to.equal('tag a not found');
-                expect(err.input).to.equal('{% a %}');
-                expect(err.line).to.equal(1);
-            });
+            return expect(engine.parseAndRender('{% a %}')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.name).to.equal('ParseError');
+                    expect(err.message).to.contain('tag a not found');
+                });
         });
 
-        it('should throw ParseError when tag not closed', function() {
-            return engine.parseAndRender('{% if %}').catch(function(err) {
-                expect(err.name).to.equal('ParseError');
-                expect(err.message).to.equal('tag {% if %} not closed');
-                expect(err.input).to.equal('{% if %}');
-                expect(err.line).to.equal(1);
+        it('should contain template content in err.message', function() {
+            var html = ['1st', '2nd', '3rd', 'X{% a %} {% enda %} Y', '5th', '6th', '7th'];
+            var message = [
+                'tag a not found',
+                '   2| 2nd',
+                '   3| 3rd',
+                '>> 4| X{% a %} {% enda %} Y',
+                '   5| 5th',
+                '   6| 6th',
+                '   7| 7th'
+            ];
+            return expect(engine.parseAndRender(html.join('\n'))).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.message).to.equal(message.join('\n'));
+                    expect(err.name).to.equal('ParseError');
+                });
+        });
+
+        it('should handle err.message when context not enough', function() {
+            var html = ['1st', 'X{% a %} {% enda %} Y', '3rd', '4th'];
+            var message = [
+                'tag a not found',
+                '   1| 1st',
+                '>> 2| X{% a %} {% enda %} Y',
+                '   3| 3rd',
+                '   4| 4th'
+            ];
+            return expect(engine.parseAndRender(html.join('\n'))).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.message).to.equal(message.join('\n'));
+                });
+        });
+
+        it('should contain the whole template content in err.input', function() {
+            var html = 'bar\nfoo{% a %}\nfoo';
+            return expect(engine.parseAndRender(html)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.input).to.equal(html);
+                });
+        });
+
+        it('should contain line number in err.line', function() {
+            var html = '<html>\n<head>\n\n{% raw %}\n\n';
+            return expect(engine.parseAndRender(html)).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.line).to.equal(4);
+                });
+        });
+
+        it('should contain stack in err.stack', function() {
+            return expect(engine.parseAndRender('{% -a %}')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    expect(err.stack).to.contain('AssertionError: tag -a not found');
+                    expect(err.stack).to.contain('at Object._tagInstance.parse');
+                });
+        });
+
+        it('should contain file path in err.file', function() {
+            var html = '<html>\n<head>\n\n{% raw %}\n\n';
+            mock({
+                "/foo.html": html
             });
+            return expect(engine.renderFile('/foo.html')).to.eventually
+                .be.rejected
+                .then(function(err) {
+                    mock.restore();
+                    expect(err.name).to.equal('ParseError');
+                    expect(err.file).to.equal('/foo.html');
+                });
         });
     });
 });

test/util/underscore.js

@@ -1,11 +1,28 @@
 const chai = require("chai");
 const sinon = require('sinon');
 const expect = chai.expect;
+const Errors = require('../../src/util/error.js');
 chai.use(require("sinon-chai"));
 
 var _ = require('../../src/util/underscore.js');
 
 describe('util/underscore', function() {
+    describe('.isError()', function() {
+        it('should return true for new Error', function() {
+            expect(_.isError(new Error())).to.be.true;
+        });
+        it('should return true for RenderError', function() {
+            var tpl = {
+                token: {
+                    input: 'xx'
+                }
+            };
+            expect(_.isError(new Errors.RenderError(new Error(), tpl))).to.be.true;
+        });
+        it('should return true for RenderBreakError', function() {
+            expect(_.isError(new Errors.RenderBreakError())).to.be.true;
+        });
+    });
     describe('.isString()', function() {
         it('should return true for literal string', function() {
             expect(_.isString('foo')).to.be.true;