@discoveryjs/scan-fs

@discoveryjs/scan-fs

An utility for seeking files by file system scanning and optionally populating file info with processing their content. It's like a Webpack's loaders but for extracting data from a FS and files.

Is a part of Discovery.js projects.

• How to use
• API
  • scanFs(options?: Options | string): Promise<ScanResult>
  • normalizeOptions(options: Options | string = {}): NormalizedOptions
  • Types
• Examples
• License

How to use

Install:

npm install @discoveryjs/scan-fs

Use:

import { scanFs } from '@discoveryjs/scan-fs';
// or const { scanFs } = require('@discoveryjs/scan-fs')

const { files, symlinks, errors } = scanFs({
  /* options */
});

API

scanFs(options?: Options | string): Promise

Main method that scans a file system for files and symlinks, returns an object with the following fields:

• basedir - a directory path which is using to make an absolute path for files and symlinks
• files – a list of files that meet a path requirements and match to one of rules if any
• symlinks – a list of symlinks that meet a path requirements
• errors – a list of errors occuried during file processing or symlink resolving
• pathsScanned – a number of paths which was examinated during a scanning
• filesTested – a number of file paths which was examinated by rules

A value of options parameter is a string (which equivalent to { basedir: <string> } object) or an object with all optional fields:

Note: options argument is also optional which equivalent to a call scanFs({}) or scanFs({ basedir: process.pwd() }).

• basedir

  Type: string
  Default: process.cwd()

  Base directory to scan and resolve paths to. All the paths in a result are relative to basedir.

• include

  Type: string, string[] or null
  Default: null

  A list of directories to scan relative to basedir. When used, a scanned file path must start with one of the directories from the list. include has priority over exclude option, i.e. include wins when the same path is used in include and exclude options. Paths should be specified in POSIX disregarding of used operating system.

• exclude

  Type: string, string[] or null
  Default: null

  A list of directories to avoid scan relative to basedir. When used, a file relative path must not start with any of the directories from the list. Paths should be specified in POSIX disregarding of used operating system.

• rules

  Type: Rule or Rule[]
  Default: [{}]

  rules defines which files should be added to a result and how to process them. When not set no any file will be matched. A first rule that can be applied wins, so other rules are skipping.

• resolveSymlinks

  Type: boolean
  Default: false

  Try to resolve the canonical pathname for symbolic links, the result is storing in realpath of Symlink. In case a resolving is failed or disabled the realpath field will contain null. On failure, an error is emitting with reason resolve-symlink.

• onError

  Type: function(error) or null
  Default: null

  A handler that is used when an error is occuring during FS scan or file processing. By default nothing happens, but adds to errors array which can be reached by errors field of a result.

A rule is an object with following fields (all are optional):

• test

  Type: RegExp, RegExp[] or null
  Default: null

  A list of RegExps that applies to a POSIX path relative to options.basedir.

• include

  Type: string, string[] or null
  Default: null

  The same as for options.include but applies on a rule's level. When used it also populates options.include.

• exclude

  Type: string, string[] or null
  Default: undefnullined

  The same as for options.exclude but applies on a rule's level.

• extract

  Type: function(file: File, content: string, rule: MatchRule)
  Default: undefined

  A function that extract some data from a file content. Such a function receives three arguments:

  • file – an instance of File
  • content – a string or Buffer (depends on encoding option, see below) which contain a content of file
  • rule – rule object with normalized options and basedir (as a value of options.basedir)

  On failure, an error is emitting with reason extract.

• encoding

  Type: BufferEncoding or null
  Default: 'utf8'

  Specifies an enconding for content parameter of extract callback when used. Allowed values are the same as for Node.js's Buffer (see Buffers and character encodings). When option value is set to null, the value of content is Buffer instead of string

• only

  Type: boolean
  Default: false

  When only is true only single rule applies. If several rules have truthy value for only, then first rule wins. The option is useful for debugging.

normalizeOptions(options: Options = {}): NormalizedOptions

This method is used internally to normalize options, which is reducing checking and potential errors during a FS scan. The method can be useful to understand how scanFs() transforms passed options.

Types

type Rule = {
  only?: boolean;
  test?: RegExp | RegExp[];
  include?: string | string[];
  exclude?: string | string[];
  extract?: ExtractCallback;
  encoding?: BufferEncoding | null;
};
type Options = {
  basedir?: string;
  include?: string | string[];
  exclude?: string | string[];
  rules?: Rule | Rule[];
  resolveSymlinks?: boolean;
  onError?: boolean | ((error: Error) => void);
};

type AcceptCallback = (relpath: string) => boolean;
type ExtractCallback = (file: File, content: string | Buffer, rule: MatchRule) => void;
type MatchRule = {
  basedir: string;
  accept: AcceptCallback;
  extract: ExtractCallback | null;
  encoding: BufferEncoding | null;
  config: Rule;
  test: RegExp[] | null;
  include: string[] | null;
  exclude: string[] | null;
};
type NormalizedOptions = {
  basedir: string;
  include: string[];
  exclude: string[];
  rules: MatchRule[];
  resolveSymlinks: boolean;
  onError: (error: Error) => void;
};

type ScanResult = {
  basedir: string;
  files: File[];
  symlinks: Symlink[];
  errors: ScanError[];
  pathsScanned: number;
  filesTested: number;
};

type File = {
  path: string;
  posixPath: string;
  errors?: Array<{ message: string; details: any }>;
  error(message: string, details: any): void;
};
type Symlink = {
  path: string;
  posixPath: string;
  realpath: string | null;
};
type ScanError = Error & {
  reason: 'resolve-symlink' | 'extract';
  path: string;
  toJSON(): { reason: string; path: string; message: string };
};

Examples

Find all package.json files from node_modules and extract name and dependencies from each one:

import { scanFs } from '@discoveryjs/scan-fs';

const { files } = await scanFs({
  exclude: ['.git', 'node_modules'],
  rules: [
    {
      test: /\/package.json$/,
      extract(file, content) {
        const pkg = JSON.parse(content);
        file.name = pkg.name;
        file.dependencies = pkg.dependencies;
      }
    }
  ]
});

for (const file of files) {
  console.log(file);
}

License

MIT