Merge pull request #930 from wycats/visitor-update
Add parent tracking and mutation to AST visitors
This commit is contained in:
Kevin Decker
@@ -204,6 +204,12 @@ var scanner = new ImportScanner();
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scanner.accept(ast);
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```
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The current node's ancestors will be maintained in the `parents` array, with the most recent parent listed first.
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The visitor may also be configured to operate in mutation mode by setting the `mutation` field to true. When in this mode, handler methods may return any valid AST node and it will replace the one they are currently operating on. Returning `false` will remove the given value (if valid) and returning `undefined` will leave the node in tact. This return structure only apply to mutation mode and non-mutation mode visitors are free to return whatever values they wish.
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Implementors that may need to support mutation mode are encouraged to utilize the `acceptKey`, `acceptRequired` and `acceptArray` helpers which provide the conditional overwrite behavior as well as implement sanity checks where pertinent.
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## JavaScript Compiler
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The `Handlebars.JavaScriptCompiler` object has a number of methods that may be customized to alter the output of the compiler:
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@@ -1,66 +1,109 @@
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/*jshint unused: false */
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function Visitor() {}
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import Exception from "../exception";
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import AST from "./ast";
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function Visitor() {
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this.parents = [];
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}
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Visitor.prototype = {
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constructor: Visitor,
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mutating: false,
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// Visits a given value. If mutating, will replace the value if necessary.
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acceptKey: function(node, name) {
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var value = this.accept(node[name]);
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if (this.mutating) {
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// Hacky sanity check:
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if (value && (!value.type || !AST[value.type])) {
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throw new Exception('Unexpected node type "' + value.type + '" found when accepting ' + name + ' on ' + node.type);
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}
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node[name] = value;
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}
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},
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// Performs an accept operation with added sanity check to ensure
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// required keys are not removed.
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acceptRequired: function(node, name) {
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this.acceptKey(node, name);
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if (!node[name]) {
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throw new Exception(node.type + ' requires ' + name);
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}
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},
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// Traverses a given array. If mutating, empty respnses will be removed
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// for child elements.
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acceptArray: function(array) {
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for (var i = 0, l = array.length; i < l; i++) {
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this.acceptKey(array, i);
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if (!array[i]) {
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array.splice(i, 1);
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i--;
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l--;
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}
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}
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},
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accept: function(object) {
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return object && this[object.type](object);
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if (!object) {
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return;
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}
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if (this.current) {
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this.parents.unshift(this.current);
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}
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this.current = object;
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var ret = this[object.type](object);
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this.current = this.parents.shift();
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if (!this.mutating || ret) {
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return ret;
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} else if (ret !== false) {
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return object;
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}
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},
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Program: function(program) {
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var body = program.body,
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i, l;
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for(i=0, l=body.length; i<l; i++) {
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this.accept(body[i]);
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}
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this.acceptArray(program.body);
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},
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MustacheStatement: function(mustache) {
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this.accept(mustache.sexpr);
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this.acceptRequired(mustache, 'sexpr');
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},
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BlockStatement: function(block) {
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this.accept(block.sexpr);
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this.accept(block.program);
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this.accept(block.inverse);
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this.acceptRequired(block, 'sexpr');
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this.acceptKey(block, 'program');
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this.acceptKey(block, 'inverse');
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},
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PartialStatement: function(partial) {
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this.accept(partial.partialName);
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this.accept(partial.context);
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this.accept(partial.hash);
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this.acceptRequired(partial, 'sexpr');
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},
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ContentStatement: function(content) {},
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CommentStatement: function(comment) {},
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ContentStatement: function(/* content */) {},
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CommentStatement: function(/* comment */) {},
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SubExpression: function(sexpr) {
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var params = sexpr.params, paramStrings = [], hash;
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this.accept(sexpr.path);
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for(var i=0, l=params.length; i<l; i++) {
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this.accept(params[i]);
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}
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this.accept(sexpr.hash);
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this.acceptRequired(sexpr, 'path');
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this.acceptArray(sexpr.params);
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this.acceptKey(sexpr, 'hash');
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},
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PathExpression: function(path) {},
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PathExpression: function(/* path */) {},
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StringLiteral: function(string) {},
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NumberLiteral: function(number) {},
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BooleanLiteral: function(bool) {},
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StringLiteral: function(/* string */) {},
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NumberLiteral: function(/* number */) {},
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BooleanLiteral: function(/* bool */) {},
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Hash: function(hash) {
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var pairs = hash.pairs;
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for(var i=0, l=pairs.length; i<l; i++) {
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this.accept(pairs[i]);
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}
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this.acceptArray(hash.pairs);
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},
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HashPair: function(pair) {
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this.accept(pair.value);
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this.acceptRequired(pair, 'value');
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}
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};
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+108
-3
@@ -1,7 +1,7 @@
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/*global Handlebars */
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/*global Handlebars, shouldThrow */
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describe('Visitor', function() {
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if (!Handlebars.Visitor) {
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if (!Handlebars.Visitor || !Handlebars.print) {
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return;
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}
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@@ -23,9 +23,15 @@ describe('Visitor', function() {
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};
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visitor.BooleanLiteral = function(bool) {
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equal(bool.value, true);
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equal(this.parents.length, 4);
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equal(this.parents[0].type, 'SubExpression');
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equal(this.parents[1].type, 'SubExpression');
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equal(this.parents[2].type, 'BlockStatement');
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equal(this.parents[3].type, 'Program');
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};
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visitor.PathExpression = function(id) {
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equal(/foo\.bar$/.test(id.original), true);
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equal(/(foo\.)?bar$/.test(id.original), true);
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};
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visitor.ContentStatement = function(content) {
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equal(content.value, ' ');
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@@ -36,4 +42,103 @@ describe('Visitor', function() {
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visitor.accept(Handlebars.parse('{{#foo.bar (foo.bar 1 "2" true) foo=@foo.bar}}{{!comment}}{{> bar }} {{/foo.bar}}'));
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});
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it('should return undefined');
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describe('mutating', function() {
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describe('fields', function() {
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it('should replace value', function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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visitor.StringLiteral = function(string) {
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return new Handlebars.AST.NumberLiteral(42, string.locInfo);
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};
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var ast = Handlebars.parse('{{foo foo="foo"}}');
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visitor.accept(ast);
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equals(Handlebars.print(ast), '{{ PATH:foo [] HASH{foo=NUMBER{42}} }}\n');
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});
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it('should treat undefined resonse as identity', function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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var ast = Handlebars.parse('{{foo foo=42}}');
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visitor.accept(ast);
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equals(Handlebars.print(ast), '{{ PATH:foo [] HASH{foo=NUMBER{42}} }}\n');
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});
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it('should remove false responses', function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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visitor.Hash = function() {
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return false;
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};
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var ast = Handlebars.parse('{{foo foo=42}}');
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visitor.accept(ast);
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equals(Handlebars.print(ast), '{{ PATH:foo [] }}\n');
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});
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it('should throw when removing required values', function() {
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shouldThrow(function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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visitor.SubExpression = function() {
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return false;
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};
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var ast = Handlebars.parse('{{foo 42}}');
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visitor.accept(ast);
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}, Handlebars.Exception, 'MustacheStatement requires sexpr');
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});
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it('should throw when returning non-node responses', function() {
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shouldThrow(function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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visitor.SubExpression = function() {
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return {};
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};
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var ast = Handlebars.parse('{{foo 42}}');
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visitor.accept(ast);
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}, Handlebars.Exception, 'Unexpected node type "undefined" found when accepting sexpr on MustacheStatement');
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});
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});
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describe('arrays', function() {
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it('should replace value', function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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visitor.StringLiteral = function(string) {
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return new Handlebars.AST.NumberLiteral(42, string.locInfo);
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};
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var ast = Handlebars.parse('{{foo "foo"}}');
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visitor.accept(ast);
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equals(Handlebars.print(ast), '{{ PATH:foo [NUMBER{42}] }}\n');
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});
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it('should treat undefined resonse as identity', function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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var ast = Handlebars.parse('{{foo 42}}');
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visitor.accept(ast);
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equals(Handlebars.print(ast), '{{ PATH:foo [NUMBER{42}] }}\n');
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});
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it('should remove false responses', function() {
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var visitor = new Handlebars.Visitor();
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visitor.mutating = true;
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visitor.NumberLiteral = function() {
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return false;
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};
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var ast = Handlebars.parse('{{foo 42}}');
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visitor.accept(ast);
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equals(Handlebars.print(ast), '{{ PATH:foo [] }}\n');
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});
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});
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});
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});
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