feat: Implement alternate config lookup (#18742)

* feat: Look up config file from file being linted fixes #18385 * Fix ESLint class flag lookup * Fix up tests for config lookup * Add documentation for new config lookup flag * Clean up directory searching behavior * Read config files from starting from parent * Cover edge cases * Fix failing test * Fix test and linting errors * Remove .only from tests * Fix failing test * Incorporate TypeScript config files * Fix lint errors * Fix docs link * Fix broken link * Fix conflicts * Update lib/config/config-loader.js Co-authored-by: 唯然 <[email protected]> * Update lib/config/config-loader.js Co-authored-by: 唯然 <[email protected]> * Update docs/src/use/configure/configuration-files.md Co-authored-by: Francesco Trotta <[email protected]> * Add comment about CLI overrideConfig * Remove duplicate code * Fix error * add test with a deep subdir * Remove immediate child check * Fix edge cases * Clean up logic * Ensure foo*/*.js doesn't traverse directory foo when ignored * Ensure order of glob patterns doesn't matter * Fix edge cases * Don't normalize absolute path to posix * add tests with overrideConfig and no config file * Fix config override behavior * Fix lint issues * Update docs/src/use/configure/configuration-files.md Co-authored-by: Milos Djermanovic <[email protected]> * Update docs/src/use/configure/configuration-files.md Co-authored-by: Milos Djermanovic <[email protected]> * Update lib/config/config-loader.js Co-authored-by: Milos Djermanovic <[email protected]> * Update lib/config/config-loader.js Co-authored-by: Milos Djermanovic <[email protected]> * Update lib/config/config-loader.js Co-authored-by: Milos Djermanovic <[email protected]> * Update lib/config/config-loader.js Co-authored-by: Milos Djermanovic <[email protected]> * Update directory search to group by glob parent * Simplify lookup * Remove unused package --------- Co-authored-by: 唯然 <[email protected]> Co-authored-by: Francesco Trotta <[email protected]> Co-authored-by: Milos Djermanovic <[email protected]>
eslint · Sep 25, 2024 · 2ff0e51 · 2ff0e51
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diff --git a/docs/src/use/configure/configuration-files.md b/docs/src/use/configure/configuration-files.md
@@ -499,6 +499,22 @@ npx eslint --config some-other-file.js **/*.js
 
 In this case, ESLint does not search for `eslint.config.js` and instead uses `some-other-file.js`.
 
+### Experimental Configuration File Resolution
+
+::: warning
+This feature is experimental and its details may change before being finalized. This behavior will be the new lookup behavior starting in v10.0.0, but you can try it today using a feature flag.
+:::
+
+You can use the `unstable_config_lookup_from_file` flag to change the way ESLint searches for configuration files. Instead of searching from the current working directory, ESLint will search for a configuration file by first starting in the directory of the file being linted and then searching up its ancestor directories until it finds a `eslint.config.js` file (or any other extension of configuration file). This behavior is better for monorepos, where each subdirectory may have its own configuration file.
+
+To use this feature on the command line, use the `--flag` flag:
+
+```shell
+npx eslint --flag unstable_config_lookup_from_file .
+```
+
+For more information about using feature flags, see [Feature Flags](../../flags/).
+
 ## TypeScript Configuration Files
 
 ::: warning
@@ -511,6 +527,8 @@ You need to enable this feature through the `unstable_ts_config` feature flag:
 npx eslint --flag unstable_ts_config
 ```
 
+For more information about using feature flags, see [Feature Flags](../../flags/).
+
 For Deno and Bun, TypeScript configuration files are natively supported; for Node.js, you must install the optional dev dependency [`jiti`](https://github.com/unjs/jiti) in your project (this dependency is not automatically installed by ESLint):
 
 ```bash
@@ -560,7 +578,7 @@ ESLint does not perform type checking on your configuration file and does not ap
 :::
 
 ::: warning
-As of now, [`jiti`](https://github.com/unjs/jiti) does not support [Top-level `await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await#top_level_await)
+As of now, [`jiti`](https://github.com/unjs/jiti) does not support [top-level `await`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await#top_level_await)
 :::
 
 ### Configuration File Precedence

diff --git a/lib/cli.js b/lib/cli.js
@@ -348,14 +348,9 @@ const cli = {
         // find the config file
         const {
             configFilePath,
-            basePath,
-            error
+            basePath
         } = await locateConfigFileToUse({ cwd: process.cwd(), configFile }, hasUnstableTSConfigFlag);
 
-        if (error) {
-            throw error;
-        }
-
         return ["--config", configFilePath, "--basePath", basePath];
     },