New: ignorePatterns in config files (refs eslint/rfcs#22)

[mysticatea]

What is the purpose of this pull request? (put an "X" next to item)

[X] Add something to the core.

What changes did you make? (Give an overview)

This PR implements ignorePatterns top-level property into config files. This feature has been approved in RFC 22. People can use ignorePatterns property instead of .eslintignore file. Also, people can provide the ignorePatterns setting with shareable configs. It will reduce the cost of setup of new repositories.

# .eslintrc.yml
ignorePatterns:
- /dist
- /temp
- /test.js
- "*.min.js"
extends:
- eslint:recommended
rules:
  semi: error

Detailed Design

I removed IgnoredPaths class that had been handling .eslintignore, --ignore-path, --ignore-pattern, and --no-ignore. Instead, now ConfigArray handles ignore patterns.

// Example of `ConfigArray`.
[
    { name: "DefaultIgnorePattern", ignorePattern: { /*...*/ } },
    { name: ".eslintrc.yml » eslint:recommended", /*...*/ },
    { name: ".eslintrc.yml", /*...*/ },
    { name: ".eslintignore", ignorePattern: { /*...*/ } },
    { name: "CLIOptions", ignorePattern: { /*...*/ } }, // --ignore-pattern
]

Like above, config array contains the ignore pattern data additionally if existed. It will merge ignore patterns of all config array element in the order as-is then create a node-ignore instance. This means, ignorePatterns properties will be merged in the same order as the other settings, and we can use the unignoring with !.

Classes:

• IgnorePattern class (new!)
  It has basePath and patterns as similar to OverrideTester class that handles overrides[i].files. The IgnorePattern.createIgnore() static method creates the predicate function from multiple IgnorePattern instances.
• ConfigArray class
  Now the array elements have ignorePattern property that is an IgnorePattern instance or undefined. The ConfigArray#extractConfig() method merges the IgnorePattern instances by IgnorePattern.createIgnore() static method.
• ConfigArrayFactory class
  Now it recognizes ignorePatterns top-level property in config files then creates ignorePattern properties into config array elements.
  Also, now it has new two methods factory.loadESLintIgnore(filePath) and factory.loadDefaultESLintIgnore() to load .eslintignore and something like.
• CascadingConfigArrayFactory class
  Now it recognizes --ignore-pattern, --ignore-path, and .eslintignore then creates the corresponding config array elements by a ConfigArrayFactory instance.
• FileEnumerator class
  Now it has the updated ignoring logic.
• CLIEngine class
  Now it has the updated ignoring logic in executeOnFiles(), executeOnText(), and isPathIgnored().

Tests:

• First, I moved the tests in ignored-paths.js to cli-engine.js (a630d9e). Now it tests public APIs instead of internal classes. (I'd like to test the public APIs primarily. Many tests that depend on internal structures make tough to refactor code.)
• Then, I added several tests to cli-engine.js to test isPathIgnored() and executeOnFiles() with the new feature. (executeOnText() uses isPathIgnored() internally)

Is there anything you'd like reviewers to focus on?

• Are there more tests we should?
• How do I improve the documentation?

[mysticatea]

Hmm, the test results are different from my local... 🤔

[mysticatea]

This PR is ready for review.

[platinumazure]

Just two small changes needed from my perspective.

Not sure if another person should also review. This is a pretty large commit.

[mysticatea]

I have resolved conflicts.

[kaicataldo]

LGTM, thanks!

[kaicataldo]

Still LGTM!

[platinumazure]

Just one small nit (left a suggestion), otherwise looks great. Thanks!

[kaicataldo]

Thanks! Sorry for the delay in getting this merged.

[mysticatea]

Thank you for reviewing this big PR!

[nickharris]

@mysticatea - getCommonAncestorPath introduces this issue - #12850