Catharsis

A JavaScript parser for Google Closure Compiler type expressions.

Catharsis is designed to be:

• Accurate. Catharsis is based on a PEG.js grammar that's designed to handle any valid type expression. It uses a Mocha test suite to verify the parser's accuracy.
• Fast. Parse results are cached, so the parser is invoked only when necessary.
• Flexible. Catharsis can convert parse results back into type expressions. In addition, it provides a lenient mode that can recover from common errors in type expressions.

Example

var catharsis = require('catharsis');

var type;
var malformedType;
var parsedType;
var parsedMalformedType;

// normal parsing
try {
    type = '!Object';
    parsedType = catharsis.parse(type);
    console.log('%j', parsedType);  // {"type":"NameExpression,"name":"Object","nullable":false}
}
catch(e) {
    console.error('unable to parse %s: %s', type, e);
}

// lenient parsing
try {
    malformedType = 'number|string';  // should be (number|string)
    parsedMalformedType = catharsis.parse(malformedType, {lenient: true});
}
catch (e) {
    console.error('you will not see this error, thanks to lenient mode!');
}

console.log(catharsis.stringify(parsedType));           // !Object
console.log(catharsis.stringify(parsedMalformedType));  // number|string
console.log(catharsis.stringify(parsedMalformedType,    // (number|string)
    {useCache: false}));

See the test/specs/ directory for more examples of Catharsis' parse results.

Methods

parse(type, options)

Parse the Closure Compiler type type, and return the parse results. Throws an error if the type cannot be parsed.

When called without options, Catharsis attempts to parse type expressions in the same way as Closure Compiler. When the lenient option is enabled, Catharsis can also parse several kinds of malformed type expressions:

• The string function is treated as a function type with no parameters.
• The period may be omitted from type applications. For example, Array.<string> and Array<string> will be parsed in the same way.
• The enclosing parentheses may be omitted from type unions. For example, (number|string) and number|string will be parsed in the same way.
• Name expressions may contain the characters # and ~.
• Name expressions may contain a reserved word.
• Record types may use types other than name expressions for keys.

Parameters

• type: A string containing a Closure Compiler type expression.
• options: Options for parsing the type expression.
  • options.lenient: Specifies whether to enable lenient mode. Defaults to false.
  • options.useCache: Specifies whether to use the cache of parsed types. Defaults to true.

Returns

An object containing the parse results. See the test/specs/ directory for examples of the parse results for different type expressions.

The object also includes two non-enumerable properties:

• lenient: A boolean indicating whether the type expression was parsed in lenient mode.
• typeExpression: A string containing the type expression that was parsed.

stringify(parsedType, options)

Stringify the parsed Closure Compiler type expression parsedType, and return the type expression. If validation is enabled, throws an error if the stringified type expression cannot be parsed.

Parameters

• parsedType: An object containing a parsed Closure Compiler type expression.
• options: Options for stringifying the parse results.
  • options.htmlSafe: Specifies whether to return an HTML-safe string that replaces left angle brackets (<) with the corresponding entity (<). Note: Characters in name expressions are not escaped.
  • options.useCache: Specifies whether to use the cache of stringified parse results. If the cache is enabled, and the parsed type expression includes a typeExpression property, the typeExpression property will be returned as-is. Defaults to true.
  • options.validate: Specifies whether to validate the stringified parse results by attempting to parse them as a type expression. Defaults to false.

Returns

A string containing the type expression.

Installation

With npm:

npm install catharsis

Or without:

git clone git://github.com/hegemonic/catharsis.git

Roadmap and known issues

Take a look at the issue tracker to see what's in store for Catharsis.

Bug reports, feature requests, and pull requests are always welcome! If you're working on a large pull request, please contact me in advance so I can help things go smoothly.

Note: The parse tree's format should not be considered final until Catharsis reaches version 1.0. I'll do my best to provide release notes for any changes.

Changelog

• 0.4.1 (March 2013):
  • The parse() and stringify() methods now honor all of the specified options.
  • When lenient parsing is enabled, name expressions can now contain a reserved word.
• 0.4.0 (March 2013):
  • Catharsis now supports a lenient parsing option that can parse several kinds of malformed type expressions. See the documentation for details.
  • The objects containing parse results are now frozen.
  • The objects containing parse results now have two non-enumerable properties:
    • lenient: A boolean indicating whether the type expression was parsed in lenient mode.
    • typeExpression: A string containing the original type expression.
  • The stringify() method now honors the useCache option. If a parsed type includes a typeExpression property, and useCache is not set to false, the stringified type will be identical to the original type expression.
• 0.3.1 (March 2013): Type expressions that begin with a reserved word, such as integer, are now parsed correctly.
• 0.3.0 (March 2013):
  • The parse() and stringify() methods are now synchronous, and the parseSync() and stringifySync() methods have been removed. Note: This change is not backwards-compatible with previous versions.
  • The parse results now use a significantly different format from previous versions. The new format is more expressive and is similar, but not identical, to the format used by the doctrine parser. Note: This change is not backwards-compatible with previous versions.
  • Name expressions that contain a reserved word now include a reservedWord: true property.
  • Union types that are optional or nullable, or that can be passed a variable number of times, are now parsed and stringified correctly.
  • Optional function types and record types are now parsed and stringified correctly.
  • Function types now longer include new or this properties unless the properties are defined in the type expression. In addition, the new and this properties can now use any type expression.
  • In record types, the key for a field type can now use any type expression.
  • Standalone single-character literals, such as ALL (*), are now parsed and stringified correctly.
  • null and undefined literals with additional properties, such as repeatable, are now stringified correctly.
• 0.2.0 (November 2012):
  • Added stringify() and stringifySync() methods, which convert a parsed type to a type expression.
  • Simplified the parse results for function signatures. Note: This change is not backwards-compatible with previous versions.
  • Corrected minor errors in README.md.
• 0.1.1 (November 2012): Added opts argument to parse() and parseSync() methods. Note: The change to parse() is not backwards-compatible with previous versions.
• 0.1.0 (November 2012): Initial release.

License

MIT license.