snapdragon-position

Snapdragon util and plugin for patching the position on an AST node.

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Install

Install with npm:

$ npm install --save snapdragon-position

What does this do?

Adds a .position 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 .position() method to the instance and patches the lexer.lex() and lexer.handle() methods to automatically add position objects to tokens.

There is a more detailed example below.

Heads up!

If you would prefer for the property name to be token.loc rather than token.position, use snapdragon-location 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.

position

Sets the start position and returns a function for setting the end position on a token.

Params

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

Example

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

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

const pos = position(lexer);
const token = pos(lexer.advance());
console.log(token);

.plugin

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

Example

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

.location

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

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

Example

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

.position

Returns a function for getting the current position.

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

Example

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

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

Params

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

Example

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

Params

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

Example

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

const start = new position.Location(lexer);
lexer.advance();
const end = new position.Location(lexer);
console.log(new position.Position(start, end, lexer));
// Position {
//   source: undefined,
//   start: Location { index: 0, column: 1, line: 1 },
//   end: Location { 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 position = require('snapdragon-position');
const Lexer = require('snapdragon-lexer');
const lexer = new Lexer('foo/bar');
lexer.use(position());

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

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

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

Token {
  type: 'text',
  value: 'foo',
  match: [ 'foo', index: 0, input: 'foo/*' ],
  position: {
    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;
  position: Position;
}

Position objects

The token.position property contains source string position information on the token.

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

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

Location objects

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

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

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