doc-snippets is a simple tool that allows you to extract and inject snippets from code into markdown files.

Using NPM:

npm install --save-dev doc-snippets

Using Yarn:

yarn add -D doc-snippets

doc-snippets extracts and injects snippets by using tokens:

• To mark a snippet:
  • $start: snippet-name - The start of a snippet and its name (required)
  • $end - The end of a snippet.
• To inject a snippet:
  • $snippet: snippet-name - This gets replaced by the snippet with the given name.

The snippet name is a string containing any characters except whitespace.

As soon as doc-snippets encounters any form of whitespace (space, tab, newline), the snippet name capture ends.

The doc-snippets CLI is configured using a JSON file that contains a doc-snippets object. By default, this file is package.json.

The configuration object has the following structure (and default values):

"doc-snippets": {
  "extract": {
    "include": "./**/*.{js,ts,json,yaml,txt,md,graphql,cue}",
    "ignore": "./**/node_modules/**",
    "dir": "./src"
  },
  "inject": {
    "include": "./**/*.md",
    "ignore": [],
    "dir": "./src/docs"
  },
  "startTokens": [
    {
      "pattern": "$start: ",
      "inline": false
    }
  ],
  "endTokens": [
    {
      "pattern": "$end",
      "inline": false
    }
  ],
  "injectToken": "$snippet: ",
  "outputDir": "./docs"
}

The extract and inject objects both have the same structure:

• include - a string or array of strings containing paths to include. The paths are formatted as Glob patterns following the node-glob specification
• ignore - same as include, this is a string or array of strings containing paths to ignore. It follows the same Glob pattern specification as include
• dir - the base directory for injection and extraction. include and ignore use this directory as their base when searching for files.

The extract object specifies which files will be parsed for snippets to extract.

The inject object specifies which files will be copied into outputDir and have snippets injected into them.

Example extract object:

"extract": {
  "include": ["sample.sql", "./**/*.{js,ts}"],
  "ignore": "./**/node_modules/**",
  "dir": "./src"
}

In this example, extract will perform its search within the ./src directory.

It will include:

• ./src/sample.sql
• All files within ./src and its subdirectories ending in .js and .ts

It will ignore:

• All directories and subdirectories of any node_modules directory found within ./src and its subdirectories.

The same principles apply for the inject object.

Extraction tokens mark the beginning and end of our snippets.

The tokens have two properties:

• pattern - the exact string that denotes the token
• inline - defines whether the token is a regular or inline extraction token

By default, extraction tokens are designed to be written within their own lines. Anything else written within the token's line will be ignored when extracting snippets.

Let's take a look at an example:

// $start: hello-snippet we can add comments here
const greeting = "Hello World!";
console.log(greeting);
// $end

Using the default configuration, this code will yield a snippet called hello-snippet with the following contents:

const greeting = "Hello World!";
console.log(greeting);

To allow for more flexible snippet extraction, we can use inline extraction tokens.

For example, let's configure our extraction tokens as follows:

{
  //...
  "startTokens": [
    {
      "pattern": "/* #start: {SNIPPET_NAME} */",
      "inline": true
    }
  ],
  "endTokens": [
    {
      "pattern": "/* #end */",
      "inline": true
    }
  ]
}

Note that there is a special token within the start token's pattern property: {SNIPPET_NAME}. This denotes where in the inline token the snippet name will appear.

In addition, let's assume that we have a file with the following code:

const greeting = /* #start: hello-inline-snippet */"Hello World!";
console.log(greeting);/* #end */

Snippet extraction would now yield a snippet named hello-inline-snippet with the following contents:

"Hello World!";
console.log(greeting);

Inline extraction tokens can be useful when you need to extract only part of your line.

Regular and inline extraction tokens can be used at the same time, and snippet extraction will always search for any end token after it encounters any start token.

For reference:

• When a regular start token is encoutered, snippet extraction starts at the beginning of the next line.
• When an inline start token is encountered, snippet extraction starts immediately after the token ends.
• When a regular end token is encountered, snippet extraction ends at the end of the previous line.
• When an inline end token is encountered, snippet extraction ends at the beginning of the token.

⚠️ Regular and inline snippets containing the same substring ⚠️

If we have the following configuration for our end tokens:

"endTokens": [
  {
    "pattern": "$end"
  }
  {
    "pattern": "/* $end */",
    "inline": true
  }
],

the $end regular token will always match before the inline /* $end */ token due to the way Regex matching works in Javascript.

To avoid these collisions, make sure to specify inline extraction tokens which don't contain any of your regular injection tokens as exact substrings within them.

An easy remedy for the above configuration is simply replacing /* $end */ with /* #end */:

"endTokens": [
  {
    "pattern": "$end"
  }
  {
    "pattern": "/* #end */",
    "inline": true
  }
],

The injectionToken is the exact string which will be replaced by your snippet during injection. The snippet must follow immediately after the injectionToken.

For example, if you have the following injectionToken:

{
  // Note the space character at the end
  "injectionToken": "$snippet: "
}

the following text would be replaced by a snippet called hello-snippet:

$snippet: hello-snippet

The outputDir is the output directory for the documentation injected with snippets.

doc-snippets comes with a CLI tool which is designed to handle most scenarios.

The CLI combine is the only currently supported command, and can be used as follows:

doc-snippets combine

The combine command reads a "doc-snippets" section from a configuration file (by default this is package.json) and performs snippet extraction and injection, and outputs documentation with injected snippets into an outputDir.

All configuration options can be overridden using combine's command options.

• -c --config <path> - Path to configuration file (default: './package.json')
• -o --output-dir <path> - Combined documentation output directory
• --extract-dir <path> - The base directory within which to search for snippets
• --extract-include <paths...> - Include specified paths or glob patterns in snippet extraction
• --extract-ignore <paths...> - Ignore specified paths or glob patterns in snippet extraction
• --inject-dir <path> - The base directory within which to search for injectable files
• --inject-include <paths...> - Include specified paths or glob patterns in snippet injection
• --inject-ignore <paths...> - Ignore specified paths or glob patterns in snippet injection
• --start-tokens <tokens...> - Tokens marking the start of the snippet
• --end-tokens <tokens...> - Tokens marking the end of the snippet
• --inline-start-tokens <tokens...> - Inline Tokens marking the start of the snippet
• --inline-end-tokens <tokens...> - Inline Tokens marking the end of the snippet
• --inject-token <token> - Token marking the point of snippet injection

If you want to use doc-snippets programatically, it offers two exported functions:

import { extractSnippets, injectSnippetsIntoFile } from "doc-snippets";

const searchOptions = {
  include: ["sample.sql", "./**/*.{js,ts}"],
  ignore: "./**/node_modules/**",
  dir: "./src",
};

//Returns snippets as `Record<string, string>`.
const startTokens = [
  {
    pattern: "$start: "
  },
  {
    pattern: "/* #start: {SNIPPET_NAME} */",
    inline: true
  }
];

const endTokens = [
  {
    pattern: "$end"
  },
  {
    pattern: "/* #end */",
    inline: true
  }
];

const snippets = await extractSnippets(searchOptions, startTokens, endTokens);

//Injects `snippets` into `./dest/readme.md` replacing all instances of `$snippet: snippet-name` with the appropriate snippet
await injectSnippetsIntoFile(snippets, "./dest/readme.md", "$snippet: ");