espower

espower

Power Assert feature instrumentor based on the ECMAScript AST.

DESCRIPTION

espower is a core module of power-assert family.

espower detects and manipulates assertion expression (JavaScript Code) in the form of ECMAScript AST defined in The ESTree Spec (formerly known as Mozilla SpiderMonkey Parser API), to instrument power-assert feature into returned new AST object. AST in, AST out. Since 0.11.0, espower can transform ES6 AST as well.

Please note that espower is a beta version product. Pull-requests, issue reports and patches are always welcomed. See power-assert project for more documentation.

CHANGELOG

See CHANGELOG

API

var modifiedAst = espower(originalAst, [options])

return type
object

espower function manipulates originalAst then returns modifiedAst that is also an AST node object defined in The ESTree Spec. If destructive option is falsy, originalAst will be unchanged. If destructive option is truthy, originalAst will be manipulated directly and returned modifiedAst will be the same instance of originalAst.

espower function throws EspowerError when

• originalAst is already instrumented
• originalAst does not contain location information
• options argument is not valid

originalAst

type	default value
object	N/A

originalAst should be an AST node object defined in The ESTree Spec.

options

type	default value
object	(return value of espower.defaultOptions())

Configuration options. If not passed, default options will be used.

options.destructive

type	default value
boolean	false

Modify originalAst destructively or not.

If false, espower clones originalAst deeply, so originalAst will be unchanged. If true, originalAst will be manipulated directly and returned modifiedAst will be the same instance of originalAst.

options.patterns

type	default value
Array of string	objects shown below

[
    'assert(value, [message])',
    'assert.ok(value, [message])',
    'assert.equal(actual, expected, [message])',
    'assert.notEqual(actual, expected, [message])',
    'assert.strictEqual(actual, expected, [message])',
    'assert.notStrictEqual(actual, expected, [message])',
    'assert.deepEqual(actual, expected, [message])',
    'assert.notDeepEqual(actual, expected, [message])'
]

Target patterns for power assert feature instrumentation.

If callee name (for example, assert.equal) matches exactly and number of arguments is satisfied, then the assertion will be modified. Detection is done by escallmatch. Any arguments enclosed in bracket (for example, [message]) means optional parameters. Without bracket means mandatory parameters.

(optional) options.path

type	default value
string	N/A

Filepath of originalAst. If passed, espower stores filepath information for reporting. This property is optional.

(optional) options.sourceMap

type	default value
object or string	N/A

A raw (either as a string which can be JSON.parse'd, or an object) SourceMap associated with originalAst. This property is optional. If given, espower uses options.sourceMap to adjust information in the power-assert output.

var options = espower.defaultOptions();

Returns default options object for espower function. In other words, returns

{
    destructive: false,
    patterns: [
        'assert(value, [message])',
        'assert.ok(value, [message])',
        'assert.equal(actual, expected, [message])',
        'assert.notEqual(actual, expected, [message])',
        'assert.strictEqual(actual, expected, [message])',
        'assert.notStrictEqual(actual, expected, [message])',
        'assert.deepEqual(actual, expected, [message])',
        'assert.notDeepEqual(actual, expected, [message])'
    ]
}

EXAMPLE

For given test file example_test.js below,

var assert = require('power-assert'),
    truthy = 'true',
    falsy = 'false';
assert(falsy);
assert.equal(truthy, falsy);

Apply espower then generate modified code to console,

var espower = require('espower'),
    esprima = require('esprima'),
    escodegen = require('escodegen'),
    fs = require('fs'),
    path = require('path');

var filepath = path.join(__dirname, 'example_test.js');
var jsAst = esprima.parse(fs.readFileSync(filepath), {tolerant: true, loc: true, tokens: true});
var modifiedAst = espower(jsAst, {path: filepath});

console.log(escodegen.generate(modifiedAst));

Output:

var assert = require('power-assert'), truthy = 'true', falsy = 'false';
assert(assert._expr(assert._capt(falsy, 'arguments/0'), {
    content: 'assert(falsy)',
    filepath: '/path/to/example_test.js',
    line: 4
}));
assert.equal(assert._expr(assert._capt(truthy, 'arguments/0'), {
    content: 'assert.equal(truthy, falsy)',
    filepath: '/path/to/example_test.js',
    line: 5
}), assert._expr(assert._capt(falsy, 'arguments/1'), {
    content: 'assert.equal(truthy, falsy)',
    filepath: '/path/to/example_test.js',
    line: 5
}));

INSTALL

via npm

Install

$ npm install --save-dev espower

use espower module on browser

espower function is exported

<script type="text/javascript" src="./path/to/node_modules/espower/build/espower.js"></script>

via bower

Install

$ bower install --save-dev espower

Then load (espower function is exported)

<script type="text/javascript" src="./path/to/bower_components/espower/build/espower.js"></script>

AUTHOR

• Takuto Wada

LICENSE

Licensed under the MIT license.

Changelog

0.11.0 (2015-04-18)

Bug Fixes

• throw Error if AST is already instrumented (1d47bdc3)

Features

• ES6 support