check-examples.md

check-examples

• Options
  • captionRequired
  • exampleCodeRegex and rejectExampleCodeRegex
  • paddedIndent
  • reportUnusedDisableDirectives
• Options for Determining ESLint Rule Applicability (allowInlineConfig, noDefaultExampleRules, matchingFileName, configFile, checkEslintrc, and baseConfig)
  • Rules Disabled by Default Unless noDefaultExampleRules is Set to true
  • Options for checking other than @example (checkDefaults, checkParams, or checkProperties)
• Context and settings
• Failing examples
• Passing examples

NOTE: This rule only works in ESLint 7. For ESLint 9, please see our processors section.

Ensures that (JavaScript) examples within JSDoc adhere to ESLint rules. Also has options to lint the default values of optional @param/@arg/@argument and @property/@prop tags or the values of @default/@defaultvalue tags.

Options

The options below all default to no-op/false except as noted.

captionRequired

JSDoc specs use of an optional <caption> element at the beginning of @example.

The option captionRequired insists on a <caption> being present at the beginning of any @example.

Used only for @example.

exampleCodeRegex and rejectExampleCodeRegex

JSDoc does not specify a formal means for delimiting code blocks within @example (it uses generic syntax highlighting techniques for its own syntax highlighting). The following options determine whether a given @example tag will have the check-examples checks applied to it:

• exampleCodeRegex - Regex which whitelists lintable examples. If a parenthetical group is used, the first one will be used, so you may wish to use (?:...) groups where you do not wish the first such group treated as one to include. If no parenthetical group exists or matches, the whole matching expression will be used. An example might be "^```(?:js|javascript)([\\s\\S]*)```\s*$" to only match explicitly fenced JavaScript blocks. Defaults to only using the u flag, so to add your own flags, encapsulate your expression as a string, but like a literal, e.g., /```js.*```/gi. Note that specifying a global regular expression (i.e., with g) will allow independent linting of matched blocks within a single @example.
• rejectExampleCodeRegex - Regex blacklist which rejects non-lintable examples (has priority over exampleCodeRegex). An example might be "^`" to avoid linting fenced blocks which may indicate a non-JavaScript language. See exampleCodeRegex on how to add flags if the default u is not sufficient.

If neither is in use, all examples will be matched. Note also that even if captionRequired is not set, any initial <caption> will be stripped out before doing the regex matching.

paddedIndent

This integer property allows one to add a fixed amount of whitespace at the beginning of the second or later lines of the example to be stripped so as to avoid linting issues with the decorative whitespace. For example, if set to a value of 4, the initial whitespace below will not trigger indent rule errors as the extra 4 spaces on each subsequent line will be stripped out before evaluation.

/**
 * @example
 *     anArray.filter((a) => {
 *       return a.b;
 *     });
 */

Only applied to @example linting.

reportUnusedDisableDirectives

If not set to false, reportUnusedDisableDirectives will report disabled directives which are not used (and thus not needed). Defaults to true. Corresponds to ESLint's --report-unused-disable-directives.

Inline ESLint config within @example JavaScript is allowed (or within @default, etc.), though the disabling of ESLint directives which are not needed by the resolved rules will be reported as with the ESLint --report-unused-disable-directives command.

Options for Determining ESLint Rule Applicability (allowInlineConfig, noDefaultExampleRules, matchingFileName, configFile, checkEslintrc, and baseConfig)

The following options determine which individual ESLint rules will be applied to the JavaScript found within the @example tags (as determined to be applicable by the above regex options) or for the other tags checked by checkDefaults, checkParams, or checkProperties options. They are ordered by decreasing precedence:

• allowInlineConfig - If not set to false, will allow inline config within the @example to override other config. Defaults to true.
• noDefaultExampleRules - Setting to true will disable the default rules which are expected to be troublesome for most documentation use. See the section below for the specific default rules.
• configFile - A config file. Corresponds to ESLint's -c.
• matchingFileName - Option for a file name (even non-existent) to trigger specific rules defined in one's config; usable with ESLint .eslintrc.* overrides -> files globs, to apply a desired subset of rules with @example (besides allowing for rules specific to examples, this option can be useful for enabling reuse of the same rules within @example as with JavaScript Markdown lintable by other plugins, e.g., if one sets matchingFileName to dummy.md/*.js so that @example rules will follow rules for fenced JavaScript blocks within one's Markdown rules). (In ESLint 6's processor API and eslint-plugin-markdown < 2, one would instead use dummy.md.) For @example only.
• matchingFileNameDefaults - As with matchingFileName but for use with checkDefaults and defaulting to .jsdoc-defaults as extension.
• matchingFileNameParams - As with matchingFileName but for use with checkParams and defaulting to .jsdoc-params as extension.
• matchingFileNameProperties As with matchingFileName but for use with checkProperties and defaulting to .jsdoc-properties as extension.
• checkEslintrc - Defaults to true in adding rules based on an .eslintrc.* file. Setting to false corresponds to ESLint's --no-eslintrc. If matchingFileName is set, this will automatically be true and will use the config corresponding to that file. If matchingFileName is not set and this value is set to false, the .eslintrc.* configs will not be checked. If matchingFileName is not set, and this is unset or set to true, the .eslintrc.* configs will be checked as though the file name were the same as the file containing the example, with any file extension changed to ".md/*.js" (and if there is no file extension, "dummy.md/*.js" will be the result). This allows convenient sharing of similar rules with often also context-free Markdown as well as use of overrides as described under matchingFileName. Note that this option (whether set by matchingFileName or set manually to true) may come at somewhat of a performance penalty as the file's existence is checked by eslint.
• baseConfig - Set to an object of rules with the same schema as .eslintrc.* for defaults.

Rules Disabled by Default Unless noDefaultExampleRules is Set to true

• eol-last - Insisting that a newline "always" be at the end is less likely to be desired in sample code as with the code file convention.
• no-console - This rule is unlikely to have inadvertent temporary debugging within examples.
• no-multiple-empty-lines - This rule may be problematic for projects which use an initial newline just to start an example. Also, projects may wish to use extra lines within examples just for easier illustration purposes.
• no-undef - Many variables in examples will be undefined.
• no-unused-vars - It is common to define variables for clarity without always using them within examples.
• padded-blocks - It can generally look nicer to pad a little even if one's code follows more stringency as far as block padding.
• jsdoc/require-file-overview - Shouldn't check example for jsdoc blocks.
• jsdoc/require-jsdoc - Wouldn't expect jsdoc blocks within jsdoc blocks.
• import/no-unresolved - One wouldn't generally expect example paths to resolve relative to the current JavaScript file as one would with real code.
• import/unambiguous - Snippets in examples are likely too short to always include full import/export info.
• node/no-missing-import - See import/no-unresolved.
• node/no-missing-require - See import/no-unresolved.

For checkDefaults, checkParams, and checkProperties, the following expression-oriented rules will be used by default as well:

• quotes - Will insist on "double".
• semi - Will insist on "never".
• strict - Disabled.
• no-empty-function - Disabled.
• no-new - Disabled.
• no-unused-expressions - Disabled.
• chai-friendly/no-unused-expressions - Disabled.

Options for checking other than @example (checkDefaults, checkParams, or checkProperties)

• checkDefaults - Whether to check the values of @default/@defaultvalue tags
• checkParams - Whether to check @param/@arg/@argument default values
• checkProperties - Whether to check @property/@prop default values

Context and settings

Context	everywhere
Tags	example
Recommended	false
Options	allowInlineConfig, baseConfig, captionRequired, checkDefaults, checkEslintrc, checkParams, checkProperties, configFile, exampleCodeRegex, matchingFileName, matchingFileNameDefaults, matchingFileNameParams, matchingFileNameProperties, noDefaultExampleRules, paddedIndent, rejectExampleCodeRegex, reportUnusedDisableDirectives

Failing examples

The following patterns are considered problems:

/**
 * @example alert('hello')
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"no-alert":2,"semi":["error","always"]}},"checkEslintrc":false}]
// Message: @example error (no-alert): Unexpected alert.

/**
 * @example alert('hello')
 */
class quux {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"no-alert":2,"semi":["error","always"]}},"checkEslintrc":false}]
// Message: @example error (no-alert): Unexpected alert.

/**
 * @example ```js
 alert('hello');
 ```
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","never"]}},"checkEslintrc":false,"exampleCodeRegex":"```js([\\s\\S]*)```"}]
// Message: @example error (semi): Extra semicolon.

/**
 * @example
 *
 * ```js alert('hello'); ```
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","never"]}},"checkEslintrc":false,"exampleCodeRegex":"```js ([\\s\\S]*)```"}]
// Message: @example error (semi): Extra semicolon.

/**
 * @example
 * ```js alert('hello'); ```
 */
var quux = {

};
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","never"]}},"checkEslintrc":false,"exampleCodeRegex":"```js ([\\s\\S]*)```"}]
// Message: @example error (semi): Extra semicolon.

/**
 * @example ```
 * js alert('hello'); ```
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","never"]}},"checkEslintrc":false,"exampleCodeRegex":"```\njs ([\\s\\S]*)```"}]
// Message: @example error (semi): Extra semicolon.

/**
 * @example <b>Not JavaScript</b>
 */
function quux () {

}
/**
 * @example quux2();
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","never"]}},"checkEslintrc":false,"rejectExampleCodeRegex":"^\\s*<.*>\\s*$"}]
// Message: @example error (semi): Extra semicolon.

/**
 * @example
 * quux(); // does something useful
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"no-undef":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":true}]
// Message: @example error (no-undef): 'quux' is not defined.

/**
 * @example <caption>Valid usage</caption>
 * quux(); // does something useful
 *
 * @example
 * quux('random unwanted arg'); // results in an error
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"captionRequired":true,"checkEslintrc":false}]
// Message: Caption is expected for examples.

/**
 * @example  quux();
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"indent":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]
// Message: @example error (indent): Expected indentation of 0 spaces but found 1.

/**
 * @example test() // eslint-disable-line semi
 */
function quux () {}
// "jsdoc/check-examples": ["error"|"warn", {"checkEslintrc":false,"noDefaultExampleRules":true,"reportUnusedDisableDirectives":true}]
// Message: @example error: Unused eslint-disable directive (no problems were reported from 'semi').

/**
 * @example
 test() // eslint-disable-line semi
 */
function quux () {}
// "jsdoc/check-examples": ["error"|"warn", {"allowInlineConfig":false,"baseConfig":{"rules":{"semi":["error","always"]}},"checkEslintrc":false,"noDefaultExampleRules":true}]
// Message: @example error (semi): Missing semicolon.

/**
 * @example const j = 5;
 * quux2();
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"matchingFileName":"../../jsdocUtils.js"}]
// Message: @example warning (id-length): Identifier name 'j' is too short (< 2).

/**
 * @example const k = 5;
 * quux2();
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"configFile":".eslintrc.json","matchingFileName":"../../jsdocUtils.js"}]
// Message: @example warning (id-length): Identifier name 'k' is too short (< 2).

/**
 * @example const m = 5;
 * quux2();
 */
function quux2 () {

}
// Message: @example warning (id-length): Identifier name 'm' is too short (< 2).

/**
 * @example const i = 5;
 *   quux2()
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"paddedIndent":2}]
// Message: @example warning (id-length): Identifier name 'i' is too short (< 2).

/**
 * @example
 * const i = 5;
 * quux2()
 */
function quux2 () {

}
// Message: @example warning (id-length): Identifier name 'i' is too short (< 2).

/**
 * @example const idx = 5;
 * quux2()
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"matchingFileName":"dummy.js"}]
// Message: @example error (semi): Missing semicolon.

/**
 * @example const idx = 5;
 *
 * quux2()
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"matchingFileName":"dummy.js"}]
// Message: @example error (semi): Missing semicolon.

/**
 * @example const idx = 5;
 *
 * quux2()
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"checkEslintrc":false,"matchingFileName":"dummy.js"}]
// Message: @example error: Parsing error: The keyword 'const' is reserved

/**
 * @example // begin
 alert('hello')
 // end
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["warn","always"]}},"checkEslintrc":false,"exampleCodeRegex":"// begin[\\s\\S]*// end","noDefaultExampleRules":true}]
// Message: @example warning (semi): Missing semicolon.

/**
 * @typedef {string} Foo
 * @example <caption></caption>
 * 'foo'
 */
// "jsdoc/check-examples": ["error"|"warn", {"captionRequired":true,"checkEslintrc":false}]
// Message: Caption is expected for examples.

/**
 * @example
 * const list: number[] = [1, 2, 3]
 * quux(list);
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"parser":"@typescript-eslint/parser","parserOptions":{"ecmaVersion":6},"rules":{"semi":["error","always"]}},"checkEslintrc":false}]
// Message: @example error (semi): Missing semicolon.

/**
 * @example
 * const test = something.find((_) => {
 *   return _
 * });
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"parserOptions":{"ecmaVersion":6},"rules":{"semi":["error","always"]}}}]
// Message: @example error (semi): Missing semicolon.

/**
 * @example <caption>Say `Hello!` to the user.</caption>
 * First, import the function:
 *
 * ```js
 * import popup from './popup'
 * const aConstInSameScope = 5;
 * ```
 *
 * Then use it like this:
 *
 * ```js
 * const aConstInSameScope = 7;
 * popup('Hello!')
 * ```
 *
 * Here is the result on macOS:
 *
 * ![Screenshot](path/to/screenshot.jpg)
 */
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"parserOptions":{"ecmaVersion":2015,"sourceType":"module"},"rules":{"semi":["error","always"]}},"checkEslintrc":false,"exampleCodeRegex":"/^```(?:js|javascript)\\n([\\s\\S]*?)```$/gm"}]
// Message: @example error (semi): Missing semicolon.

/**
 * @example // begin
 alert('hello')
 // end
 * And here is another example:
 // begin
 alert('there')
 // end
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["warn","always"]}},"checkEslintrc":false,"exampleCodeRegex":"/\\/\\/ begin[\\s\\S]*?// end/g","noDefaultExampleRules":true}]
// Message: @example warning (semi): Missing semicolon.

/**
 * @example
 *   quux();
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"indent":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]
// Message: @example error (indent): Expected indentation of 0 spaces but found 2.

/**
 * @default 'abc'
 */
const str = 'abc';
// "jsdoc/check-examples": ["error"|"warn", {"checkDefaults":true}]
// Message: @default error (quotes): Strings must use doublequote.

/**
 * @param {myType} [name='abc']
 */
function quux () {
}
// "jsdoc/check-examples": ["error"|"warn", {"checkParams":true}]
// Message: @param error (quotes): Strings must use doublequote.

/**
 * @property {myType} [name='abc']
 */
const obj = {};
// "jsdoc/check-examples": ["error"|"warn", {"checkProperties":true}]
// Message: @property error (quotes): Strings must use doublequote.

/**
 * Test function.
 *
 * @example <caption>functionName (paramOne: string, paramTwo?: any,
 * paramThree?: any): boolean</caption> test()
 *
 * @param {string} paramOne Parameter description.
 * @param {any} [paramTwo] Parameter description.
 * @param {any} [paramThree] Parameter description.
 * @returns {boolean} Return description.
 */
const functionName = function (paramOne, paramTwo,
  paramThree) {
  return false;
};
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"parserOptions":{"ecmaVersion":2015,"sourceType":"module"},"rules":{"semi":["error","always"]}},"captionRequired":true,"checkEslintrc":false}]
// Message: @example error (semi): Missing semicolon.

Passing examples

The following patterns are not considered problems:

/**
 * @example ```js
 alert('hello');
 ```
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","always"]}},"checkEslintrc":false,"exampleCodeRegex":"```js([\\s\\S]*)```"}]

/**
 * @example ```js
 alert('hello');
 ```
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","always"]}},"checkEslintrc":false,"exampleCodeRegex":"/```js([\\s\\S]*)```/"}]

/**
 * @example
 * // arbitrary example content
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"checkEslintrc":false}]

/**
 * @example
 * quux(); // does something useful
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"no-undef":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]

/**
 * @example quux();
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"indent":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]

/**
 * @example <caption>Valid usage</caption>
 * quux(); // does something useful
 *
 * @example <caption>Invalid usage</caption>
 * quux('random unwanted arg'); // results in an error
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"captionRequired":true,"checkEslintrc":false}]

/**
 * @example test() // eslint-disable-line semi
 */
function quux () {}
// "jsdoc/check-examples": ["error"|"warn", {"checkEslintrc":false,"noDefaultExampleRules":true,"reportUnusedDisableDirectives":false}]

/**
 * @example
 test() // eslint-disable-line semi
 */
function quux () {}
// "jsdoc/check-examples": ["error"|"warn", {"allowInlineConfig":true,"baseConfig":{"rules":{"semi":["error","always"]}},"checkEslintrc":false,"noDefaultExampleRules":true}]

/**
 * @example ```js
 alert('hello')
 ```
 */
var quux = {

};
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"semi":["error","never"]}},"checkEslintrc":false,"exampleCodeRegex":"```js([\\s\\S]*)```"}]

/**
 * @example
 * foo(function (err) {
 *     throw err;
 * });
 */
function quux () {}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"indent":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]

/**
 * @example
 * const list: number[] = [1, 2, 3];
 * quux(list);
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"parser":"@typescript-eslint/parser","parserOptions":{"ecmaVersion":6},"rules":{"semi":["error","always"]}},"checkEslintrc":false}]

/**
 * @example const ident = 5;
 *   quux2();
 *   bar();
 */
function quux2 () {

}
// "jsdoc/check-examples": ["error"|"warn", {"paddedIndent":2}]

/**
 * @example
 * function quux() {
 *     bar();
 * }
 */
function quux () {

}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"rules":{"indent":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]

// Comment
a();

export default {};

/**
 *
 */
function f () {

}

/**
 * Does quux
 * @example
 * // Do it!
 * quux();
 */
function quux () {
}
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"plugins":["jsdoc"],"rules":{"jsdoc/require-file-overview":["error"]}},"checkEslintrc":false,"noDefaultExampleRules":false}]

/**
 * @default "abc"
 */
const str = 'abc';
// "jsdoc/check-examples": ["error"|"warn", {"checkDefaults":true}]

/**
 * @default
 */
const str = 'abc';
// "jsdoc/check-examples": ["error"|"warn", {"checkDefaults":true}]

/**
 * @param {myType} [name="abc"]
 */
function quux () {
}
// "jsdoc/check-examples": ["error"|"warn", {"checkParams":true}]

/**
 * @param {myType} name
 */
function quux () {
}
// "jsdoc/check-examples": ["error"|"warn", {"checkParams":true}]

/**
 * @property {myType} [name="abc"]
 */
const obj = {};
// "jsdoc/check-examples": ["error"|"warn", {"checkProperties":true}]

/**
 * @property {myType} [name]
 */
const obj = {};
// "jsdoc/check-examples": ["error"|"warn", {"checkProperties":true}]

/**
 * @default 'abc'
 */
const str = 'abc';
// "jsdoc/check-examples": ["error"|"warn", {"checkDefaults":false,"matchingFileNameDefaults":"dummy.js"}]

/**
 * @param {myType} [name='abc']
 */
function quux () {
}
// "jsdoc/check-examples": ["error"|"warn", {"checkParams":false,"matchingFileNameParams":"dummy.js"}]

/**
 * @property {myType} [name='abc']
 */
const obj = {};
// "jsdoc/check-examples": ["error"|"warn", {"checkProperties":false,"matchingFileNameProperties":"dummy.js"}]

/**
 * Test function.
 *
 * @example <caption>functionName (paramOne: string, paramTwo?: any,
 * paramThree?: any): boolean</caption> test();
 *
 * @param {string} paramOne Parameter description.
 * @param {any} [paramTwo] Parameter description.
 * @param {any} [paramThree] Parameter description.
 * @returns {boolean} Return description.
 */
const functionName = function (paramOne, paramTwo,
  paramThree) {
  return false;
};
// "jsdoc/check-examples": ["error"|"warn", {"baseConfig":{"parserOptions":{"ecmaVersion":2015,"sourceType":"module"},"rules":{"semi":["error","always"]}},"captionRequired":true,"checkEslintrc":false}]