snapdragon-location

Adds a location object to snapdragon token or AST node.

Please consider following this project's author, Jon Schlinkert, and consider starring the project to show your :heart: and support.

Install

Install with npm:

$ npm install --save snapdragon-location

What does this do?

Adds a .loc object to tokens that looks something like this:

{
  source: 'string',
  start: { index: 0, column: 1, line: 1 },
  end: { index: 3, column: 4, line: 1 },
  range: [0, 3] // getter
}

When used as snapdragon-lexer plugin, this adds a .location() method to the instance and patches the lexer.lex() and lexer.handle() methods to automatically add location objects to tokens.

There is a more detailed example below.

Heads up!

If you prefer .position over .loc, use snapdragon-position instead.

API

The main export is a function that can be used as a plugin with snapdragon-lexer, or called directly with an instance of snapdragon-lexer.

location

Sets the start location and returns a function for setting the end location.

Params

• name {String|Object}: (optional) Snapdragon Lexer or Tokenizer instance, or the name to use for the location property on the token. Default is toc.
• target {Object}: Snapdragon Lexer or Tokenizer instance
• returns {Function}: Returns a function that takes a token as its only argument

Example

const location = require('snapdragon-location');
const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');

lexer.capture('slash', /^\//);
lexer.capture('text', /^\w+/);

const loc = location(lexer);
const token = loc(lexer.advance());
console.log(token);

.plugin

Use as a plugin to add a .location method to your snapdragon-lexer or [snapdragon-tokenizer][] instance to automatically add a location object to tokens when the .lex() or .handle() methods are used.

Example

const Lexer = require('snapdragon-lexer');
const location = require('snapdragon-location');
const lexer = new Lexer();
lexer.use(location());

.position

Get the current source position, with index, column and line. Used by .location() to create the "start" and "end" positions.

• returns {Object}: Returns an object with the current source position.

Example

const Lexer = require('snapdragon-lexer');
const lexer = new Lexer();
console.log(lexer.position());
//=> Position { index: 0, column: 0, line: 1 };

.location

Returns a function for getting the current location.

• returns {Function}: Returns a function that takes a token as its only argument, and patches a .loc property onto the token.

Example

const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');
lexer.use(location());

lexer.set('text', function(tok) {
  // get start location before advancing lexer
  const loc = this.location();
  const match = this.match(/^\w+/);
  if (match) {
    // get end location after advancing lexer (with .match)
    return loc(this.token(match));
  }
});

Params

• start {Object}: (required) Starting position
• end {Object}: (required) Ending position
• target {Object}: (optional) Snapdragon Lexer or Tokenizer instance
• returns {Object}

Example

const Lexer = require('snapdragon-lexer');
const Position = require('snapdragon-location').Position;
const lexer = new Lexer('foo/bar');
lexer.capture('text', /^\w+/);
lexer.advance();
console.log(new Position(lexer));
//=> Position { index: 3, column: 4, line: 1 }

Params

• start {Object}: (required) Starting position
• end {Object}: (required) Ending position
• target {Object}: (optional) Snapdragon Lexer or Tokenizer instance
• returns {Object}

Example

const Lexer = require('snapdragon-lexer');
const location = require('snapdragon-position');
const lexer = new Lexer('foo/bar')
  .capture('slash', /^\//)
  .capture('text', /^\w+/);

const start = new location.Position(lexer);
lexer.advance();
const end = new location.Position(lexer);
console.log(new location.Location(start, end, lexer));
// Location {
//   source: undefined,
//   start: Position { index: 0, column: 1, line: 1 },
//   end: Position { index: 3, column: 4, line: 1 } }

Plugin usage

When used as a plugin, this adds a .position() method to a snapdragon-lexer instance, for adding position information to tokens.

Example

const location = require('snapdragon-location');
const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');
lexer.use(location());

lexer.capture('slash', /^\//);
lexer.capture('text', /^\w+/);

var token = lexer.advance();
console.log(token);

Adds a .loc object to the token, like this:

Token {
  type: 'text',
  value: 'foo',
  match: [ 'foo', index: 0, input: 'foo/*' ],
  loc: {
    start: { index: 0, column: 1, line: 1 },
    end: { index: 3, column: 4, line: 1 },
    range: [0, 3] // getter
  } 
}

Token objects

See the Token documentation for more details about the Token object.

interface Token {
  type: string;
  value: string;
  match: array | undefined;
  loc: Location;
}

Location objects

The token.loc property contains source string location information on the token.

interface Location {
  source: string | undefined;
  start: Position;
  end: Position;
  range: array (getter)
}

• source {string|undefined} - the source location provided by lexer.options.source. Typically this is a filename, but could also be string or any user defined value.
• start {object} - start position object, which is the position of the first character of the lexed source string.
• end {object} - end position object, which is the position of the last character of the lexed source string.
• range {array} - getter that returns an array with the following values: [loc.start.index, loc.end.index]

Position objects

Each Position object consists of an index number (0-based), a column number (0-based), and a line number (1-based):

interface Position {
  index: number; // >= 0
  column: number; // >= 0,
  line: number; // >= 1
}

• line {string|undefined} - the source location provided by lexer.options.source. Typically this is a filename, but could also be string or any user defined value.
• column {object} - start position object, which is the position of the first character of the lexed source string.
• end {object} - end position object, which is the position of the last character of the lexed source string.

Example usage

const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/*', { source: 'string' });
lexer.use(location());
lexer.capture('star', /^\*/);
lexer.capture('slash', /^\//);
lexer.capture('text', /^\w+/);

lexer.tokenize();
console.log(lexer.tokens);

Results in:

[
  {
    type: 'text',
    val: 'foo',
    match: ['foo', index: 0, input: 'foo/*'],
    loc: {
      source: 'string',
      start: { index: 0, column: 1, line: 1 },
      end: { index: 3, column: 4, line: 1 },
      range: [0, 3]
    }
  },
  {
    type: 'slash',
    val: '/',
    match: ['/', index: 0, input: '/*'],
    loc: {
      source: 'string',
      start: { index: 3, column: 4, line: 1 },
      end: { index: 4, column: 5, line: 1 },
      range: [3, 4]
    }
  },
  {
    type: 'star',
    val: '*',
    match: ['*', index: 0, input: '*'],
    loc: {
      source: 'string',
      start: { index: 4, column: 5, line: 1 },
      end: { index: 5, column: 6, line: 1 },
      range: [4, 5]
    }
  }
]

About

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

Please read the contributing guide for advice on opening issues, pull requests, and coding standards.

Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

$ npm install && npm test

(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)

To generate the readme, run the following command:

$ npm install -g verbose/verb#dev verb-generate-readme && verb

Related projects

You might also be interested in these projects:

• snapdragon-capture: Snapdragon plugin that adds a capture method to the parser instance. | homepage
• snapdragon-node: Snapdragon utility for creating a new AST node in custom code, such as plugins. | homepage
• snapdragon-util: Utilities for the snapdragon parser/compiler. | homepage

Author

Jon Schlinkert

• linkedin/in/jonschlinkert
• github/jonschlinkert
• twitter/jonschlinkert

License

Copyright © 2018, Jon Schlinkert. Released under the MIT License.

This file was generated by verb-generate-readme, v0.6.0, on January 08, 2018.