vfile-location

vfile utility to convert between point (line/column) and offset (range) based locations

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • Location([file][, start])
    • Location#indices
    • Location#offset([point])
    • Location#place
    • Location#point([offset])
    • Location#start
  • Column
  • Indices
  • Line
  • Offset
  • Point
  • SerializedPoint
• Types
• Contribute

What is this?

This is a tiny but useful package that facilitates conversions between points and offsets in a file.

When should I use this?

This utility is useful when adding positional information to unist nodes, or when building packages that require location data, such as a set of lint rules.

Install

This package is ESM only.

In Node.js (version 18+) with yarn:

1yarn add @flex-development/vfile-location

See Git - Protocols | Yarn  for details regarding installing from Git.

In Deno with esm.sh:

1import { Location } from 'https://esm.sh/@flex-development/vfile-location'

In browsers with esm.sh:

1<script type="module">
2  import { Location } from 'https://esm.sh/@flex-development/vfile-location'
3</script>

Use

1import { Location, type Point } from '@flex-development/vfile-location'
2import { read } from 'to-vfile'
3import type * as unist from 'unist'
4import type { VFile, Value } from 'vfile'
5
6const point: Point = { column: 1, line: 21, offset: 474 }
7const pt: Point = { column: 2, line: 47, offset: 1124 }
8
9const file: VFile = await read('hrt.ts')
10const val: Value = String(file).slice(point.offset, pt.offset + 1)
11
12const location: Location = new Location(file)
13const loc: Location = new Location(val, point)
14
15console.log(location.offset({ ...point, offset: undefined })) // => point.offset
16console.log(location.point(point.offset)) // => point
17
18console.log(loc.offset({ ...pt, offset: undefined })) // => pt.offset
19console.log(loc.point(pt.offset)) // => pt

API

This package exports the identifier Location. There is no default export.

Location([file][, start])

Create a new location index to translate between point and offset based locations in file.

Pass a start point to make relative conversions. Any point or offset accessed will be relative to the given point.

An incremental index can be built when file is null or undefined, in which case indices (and place) must be updated manually.

• file (Value | VFile | null | undefined) — file to index
• start (Point | null | undefined) — point before first character

Location#indices

(Indices) Map, where each key/value pair is either the index of a character in the file (offset) and a point, or a line and column in the file and an offset. Both the key and value are relative to start.

Location#offset([point])

Get an offset for point.

👉 The offset for point is greater than or equal to 0 when point is valid, and -1 when point is invalid.

Parameters

• point (unist.Point | null | undefined) — place in file

Returns

(Offset) Index of character in file or -1.

Location#place

(Point) Current point.

👉 Useful for building an incremental index. This point is deeply equal to start when a file is auto-indexed and never altered.

Location#point([offset])

Get a point for offset.

👉 point.column and point.line are greater than or equal to 1 when offset is valid, and -1 when offset is invalid.

Parameters

• offset (Offset | null | undefined) — index of character in file

Returns

(Point) Place in file.

Location#start

(Readonly<Point>) Point before first character in file.

Column

Column in a source file (1-indexed integer) (TypeScript type).

1type Column = number

Indices

Map, where each key/value pair is either the index of a character in a source file (offset) and a point, or a line and column in the source file and an offset (TypeScript type).

1type Indices = { [offset: Offset]: Point; [point: SerializedPoint]: Offset }

Line

Line in a source file (1-indexed integer) (TypeScript type).

1type Line = number

Offset

Index of a character in a source file (0-indexed integer) (TypeScript type).

1type Offset = number

Point

One place in a source file (TypeScript interface).

Properties

• column (Column) — column in source file (1-indexed integer)
• line (Line) — line in source file (1-indexed integer)
• offset (Offset) — index of character in source file (0-indexed integer)

SerializedPoint

String representing one place in a source file (TypeScript type).

1type SerializedPoint = `${Line}:${Column}`

Types

This package is fully typed with TypeScript.

Contribute

See CONTRIBUTING.md.

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