init

.editorconfig

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+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.md]
+trim_trailing_whitespace = false

.gitattributes

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+* text=auto

.gitignore

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+coverage
+node_modules

.travis.yml

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+dist: trusty
+branches:
+  except: /^v\d/
+language: node_js
+node_js: node
+script: npm run-script pretest && npm run-script coverage
+after_script:
+  - npm install istanbul-coveralls
+  - node node_modules/.bin/istanbul-coveralls

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2017 Shinnosuke Watanabe
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

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+# get-processor-ids-from-stylelint-options
+
+[![NPM version](https://img.shields.io/npm/v/get-processor-ids-from-stylelint-options.svg)](https://www.npmjs.com/package/get-processor-ids-from-stylelint-options)
+[![Build Status](https://travis-ci.org/shinnn/get-processor-ids-from-stylelint-options.svg?branch=master)](https://travis-ci.org/shinnn/get-processor-ids-from-stylelint-options)
+[![Coverage Status](https://img.shields.io/coveralls/shinnn/get-processor-ids-from-stylelint-options.svg)](https://coveralls.io/github/shinnn/get-processor-ids-from-stylelint-options?branch=master)
+
+Get [stylelint](https://stylelint.io/) [processor](https://stylelint.io/user-guide/processors/) identifiers from a [stylelint option object](https://stylelint.io/user-guide/node-api/#options)
+
+```javascript
+const getProcessorIdsFromStylelintOptions = require('get-processor-ids-from-stylelint-options');
+
+getProcessorIdsFromStylelintOptions({
+  config: {
+    processors: [
+      '@mapbox/stylelint-processor-markdown',
+      ['./custom-proessor.js', {
+        optionOne: true,
+        optionTwo: false
+      }]
+    ]
+  }
+}); //=> Set {'@mapbox/stylelint-processor-markdown', './custom-processor.js'}
+```
+
+## Installation
+
+[Use npm.](https://docs.npmjs.com/cli/install)
+
+```
+npm install get-processor-ids-from-stylelint-options
+```
+
+## API
+
+```javascript
+const getProcessorIdsFromStylelintOptions = require('get-processor-ids-from-stylelint-options');
+```
+
+### getProcessorIdsFromStylelintOptions([*options*])
+
+*options*: `Object` ([stylelint API options](https://github.com/stylelint/stylelint/blob/master/docs/user-guide/node-api.md#options))  
+Return: `Set<string>`
+
+```javascript
+getProcessorIdsFromStylelintOptions({
+  config: {
+    processors: [
+      './processor0.js',
+      './processor1.js'
+    ]
+  }
+}); //=> Set {'./processor0.js', ./processor1.js'}
+
+getProcessorIdsFromStylelintOptions({
+  configOverrides: {
+    processors: '/processor/can/be/a/string/instead/of/an/array.js'
+  }
+}); //=> Set {'/processor/can/be/a/string/instead/of/an/array.js'}
+
+getProcessorIdsFromStylelintOptions({
+  config: {},
+  configOverrides: {
+    processors: 'configOverrides/will/be/ignored/when/both/config/and/configOverrides/are/provided'
+  }
+}); //=> Set {}
+
+getProcessorIdsFromStylelintOptions(); //=> Set {}
+```
+
+## License
+
+Copyright (c) 2017 [Shinnosuke Watanabe](https://github.com/shinnn)
+
+Licensed under [the MIT License](./LICENSE).

index.js

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+/*!
+ * get-processor-ids-from-stylelint-options | MIT (c) Shinnosuke Watanabe
+ * https://github.com/shinnn/get-processor-ids-from-stylelint-options
+*/
+'use strict';
+
+const {inspect} = require('util');
+
+const isPlainObject = require('lodash/isPlainObject');
+
+const props = new Set(['config', 'configOverrides']);
+
+module.exports = function getProcessorIdsFromStylelintOptions(...args) {
+  const argLen = args.length;
+
+  if (argLen === 0) {
+    return new Set();
+  }
+
+  if (argLen !== 1) {
+    throw new TypeError(`Expected 0 or 1 argument ([object]), but got ${argLen} arguments instead.`);
+  }
+
+  const options = args[0];
+
+  if (!isPlainObject(options)) {
+    throw new TypeError(`Expected the argument to be an object of stylelint API options, but got ${
+      inspect(options)
+    }.`);
+  }
+
+  for (const prop of props) {
+    const val = options[prop];
+
+    if (val) {
+      if (!isPlainObject(val)) {
+        throw new TypeError(`Expected \`${prop}\` option in stylelint API to be an object, but it was ${
+          inspect(val)
+        }.`);
+      }
+
+      if (val.processors) {
+        if (typeof val.processors === 'string') {
+          return new Set([val.processors]);
+        }
+
+        if (Array.isArray(val.processors)) {
+          const ids = new Set();
+
+          for (const processor of val.processors) {
+            ids.add(Array.isArray(processor) ? processor[0] : processor);
+          }
+
+          return ids;
+        }
+
+        throw new TypeError(
+          `\`processors\` property in the sytylelint config must be an array or a string, but it was ${
+            inspect(val.processors)
+          }.`
+        );
+      }
+    }
+  }
+
+  return new Set();
+};

package.json

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+{
+  "name": "get-processor-ids-from-stylelint-options",
+  "version": "1.0.0",
+  "description": "Get stylelint processor identifiers from given stylelint API options",
+  "repository": "shinnn/get-processor-ids-from-stylelint-options",
+  "author": "Shinnosuke Watanabe (https://github.com/shinnn)",
+  "scripts": {
+    "pretest": "eslint --fix --format=codeframe index.js test.js",
+    "test": "node --throw-deprecation test.js",
+    "coverage": "istanbul cover --print=both test.js"
+  },
+  "license": "MIT",
+  "files": [
+    "index.js"
+  ],
+  "keywords": [
+    "mode",
+    "file",
+    "stat",
+    "lstat",
+    "int",
+    "integer",
+    "number",
+    "promise",
+    "async",
+    "asynchronous"
+  ],
+  "dependencies": {
+    "lodash": "^4.17.4"
+  },
+  "devDependencies": {
+    "@shinnn/eslint-config-node": "^3.0.0",
+    "eslint": "^3.16.0",
+    "istanbul": "^0.4.5",
+    "tape": "^4.6.3"
+  },
+  "eslintConfig": {
+    "extends": "@shinnn/node"
+  }
+}

test.js

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+'use strict';
+
+const {inspect} = require('util');
+
+const main = require('.');
+const test = require('tape');
+const cloneDeep = require('lodash/cloneDeep');
+
+test('getProcessorIdsFromStylelintOptions()', t => {
+  const option = {
+    configOverrides: {
+      processors: '@mapbox/stylelint-processor-markdown'
+    }
+  };
+  const clonedOption = cloneDeep(option);
+
+  const result = main(option);
+
+  t.ok(result instanceof Set, 'should return a Set instance.');
+  t.deepEqual(
+    [...result],
+    ['@mapbox/stylelint-processor-markdown'],
+    'should get stylelint processor identifiers.'
+  );
+
+  t.deepEqual(option, clonedOption, 'should not mutate arguments.');
+
+  t.strictEqual(
+    inspect(main({
+      config: {
+        processors: [
+          ['stylelint-processor-arbitrary-tags', {startTag: '***'}],
+          './custom-processor.js'
+        ]
+      },
+      configOverrides: {
+        processors: 'stylelint-processor-html'
+      }
+    }), {breakLength: Infinity}),
+    'Set { \'stylelint-processor-arbitrary-tags\', \'./custom-processor.js\' }',
+    'should ignore `configOverrides` if `config` is provided.'
+  );
+
+  t.strictEqual(
+    main({
+      config: {
+        processors: []
+      }
+    }).size,
+    0,
+    'should return an empty set if the config has an empty `processor` option.'
+  );
+
+  t.strictEqual(
+    main({
+      config: {}
+    }).size,
+    0,
+    'should return an empty set if the config doesn\'t have `processor` option.'
+  );
+
+  t.strictEqual(
+    main({}).size,
+    0,
+    'should return an empty set if the object has neither `config` nor `configOverrides`.'
+  );
+
+  t.strictEqual(
+    main().size,
+    0,
+    'should return an empty set if it takes no arguments.'
+  );
+
+  t.throws(
+    () => main({}, {}),
+    /^TypeError.*Expected 0 or 1 argument \(\[object]\), but got 2 arguments instead\./,
+    'should throw an error when it takes too many arguments.'
+  );
+
+  t.throws(
+    () => main(['Hi']),
+    /^TypeError.*Expected the argument to be an object of stylelint API options, but got \[ 'Hi' ]\./,
+    'should throw an error when it takes a non-plain object.'
+  );
+
+  t.throws(
+    () => main({
+      config: Buffer.from('?'),
+      configOverrides: {}
+    }),
+    /^TypeError.*Expected `config` option in stylelint API to be an object, but it was <Buffer 3f>\./,
+    'should throw an error when the config object is not a plain object.'
+  );
+
+  t.throws(
+    () => main({
+      config: {
+        processors: new Map()
+      }
+    }),
+    /^TypeError.*`processors` property in the sytylelint config must be an array or a string, but it was Map \{\}\./,
+    'should throw an error when `processor` option is neither an array nor a string.'
+  );
+
+  t.end();
+});