grunt-transform

The grunt task to walk the syntax tree, and apply the transformation whenever necessary

Based on Espree (an actively-maintained fork of Esprima) API and used the same AST

Getting Started

This plugin requires Grunt ~0.4.5

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install grunt-transform --save-dev

Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:

grunt.loadNpmTasks('grunt-transform');

grunt-transform task

Run this task with the grunt transform command.

Task targets, files and options may be specified according to the grunt Configuring tasks guide.

Options

tree

Type: Object
Default: {range: true}

A complete list of available options:

Option	When set to true
range	Nodes have an index-based location range (array)
loc	Nodes have line and column-based location info
raw	Literals have extra property which stores the verbatim source
tokens	An extra array containing all found tokens
comment	An extra array containing all line and block comments
tolerant	An extra array containing all errors found, attempts to continue parsing when an error is encountered

For more details see the Esprima documentation

features

Type: Object
Default: {blockBindings: true}

A complete list of available ECMAScript 6 features:

Feature	When set to true
arrowFunctions	Enable parsing of arrow functions
blockBindings	Enable parsing of let/const
destructuring	Enable parsing of destructured arrays and objects
regexYFlag	Enable parsing of regular expression y flag
regexUFlag	Enable parsing of regular expression u flag
templateStrings	Enable parsing of template strings
binaryLiterals	Enable parsing of binary literals
octalLiterals	Enable parsing of ES6 octal literals
unicodeCodePointEscapes	Enable parsing unicode code point escape sequences
defaultParams	Enable parsing of default parameters
restParams	Enable parsing of rest parameters
forOf	Enable parsing of for-of statement
objectLiteralComputedProperties	Enable parsing computed object literal properties
objectLiteralShorthandMethods	Enable parsing of shorthand object literal methods
objectLiteralShorthandProperties	Enable parsing of shorthand object literal properties
objectLiteralDuplicateProperties	Allow duplicate object literal properties (except 'proto')
generators	Enable parsing of generators/yield
spread	Enable parsing spread operator
classes	Enable parsing classes
modules	Enable parsing of modules
jsx	Enable React JSX parsing
globalReturn	Enable return in global scope

For more details see the Espree documentation

process

Type: Function (traverse, source)
Default: (traverse, source) => source;

This option as an advanced way to control the file contents that are created.

A complete list of available arguments:

Argument	When set to true
traverse	An object with pre and post visitors
source	Source code

Depth-first traversal types

Pre-order type:

1. Display the data part of root element (or current element)
2. Traverse the left subtree by recursively calling the pre-order function.
3. Traverse the right subtree by recursively calling the pre-order function.

Post-order type:

1. Traverse the left subtree by recursively calling the post-order function.
2. Traverse the right subtree by recursively calling the post-order function.
3. Display the data part of root element (or current element).

The trace of a traversal is called a sequentialisation of the tree. The traversal trace is a list of each visited root node. No one sequentialisation according to pre-, in- or post-order describes the underlying tree uniquely. Given a tree with distinct elements, either pre-order or post-order paired with in-order is sufficient to describe the tree uniquely.

For more details see the ast-traverse documentation

Usage Example

var Alter = require('string-alter');
 
module.exports = function (grunt) {
    grunt.config.init({
        transform: {
            test: {
                options: {
                    tree: {
                        loc: true
                    },
 
                    process: function (traverse, source) {
                        var alter = new Alter(source);
 
                        traverse.pre(function (node) {
                            if (node.type === 'FunctionDeclaration') {
                                var where = JSON.stringify(node.loc, null, '\t');
 
                                alter.wrap(
                                    node.range[0],
                                    node.range[1],
                                    'try {',
                                    '} catch (error) { console.log("FD:",' + where + ') }'
                                );
                            }
                        });
 
                        return alter.apply();
                    }
                },
 
                files: {
                    'cache/actual.js': [ 'tests/fixtures/**/*.js' ]
                }
            }
        },
    });
 
    grunt.loadNpmTasks('grunt-transform');
    grunt.registerTask('default', ['transform']);
};

Input

function foo () {
    return 1;
}

Output

try {
    function foo () {
        return 1;
    }
}
catch (error) {
    console.log("FD:",{
        "start": {
            "line": 13,
            "column": 0
        },
        "end": {
            "line": 15,
            "column": 1
        }
    );
}

A list of popular ast transformers

falafel
burrito
string-alter

Tests

grunt test

License

MIT

Links

Esprima online parser
Esprima documentation
Espree
Depth-first search
Tree traversal

Task submitted by Alexander Abashkin