As we prepare for alpha release of JS plugins, it feels like we can remove the warning logged to stderr.
```
WARNING: JS plugins are experimental and not subject to semver.
Breaking changes are possible while JS plugins support is under development.
```
They do still remain experimental, but I don't think we need to shout that quite as loudly now.
This ensures that we print the expected number of rules for users that are using JS Plugins.
Fix#17519.
Based on #17517, because otherwise we'd end up with weird snapshot differences when trying to merge these anyway.
AI Disclosure: The fix here was generated with Copilot + GitHub's Raptor mini model.
For a while, we've been skipping the printing of rule runs unless `--disable-nested-config` was passed. This was a result of the nested_configs value including the base config (see #16356). When we were checking whether that value was empty, it would always have at least 1 item (unless nested configs were entirely disabled).
As part of this, I've updated some configs in the fixtures to disable correctness rules, otherwise we will end up with a bunch of fixture snapshots needing updates every time a new default rule is added.
It's probably easiest to review this one commit at a time.
ESLint has undocumented `getRange` and `getLoc` methods on `SourceCode`. Add them.
These are the last 2 missing methods on `SourceCode` (according to Claude).
Also add more tests for correct functioning of `range` and `loc` properties.
Add a getter `lineStartIndices` to `SourceCode`. ESLint has this property, but it's undocumented. Possible that some ESLint plugins rely on it (if it's there, people will use it!).
Only 1 file is linted at a time, so it's unnecessary for each rule to have its own instance of `SourceCode`. Replace `SourceCode` class with a singleton object `SOURCE_CODE` which is reused for all rules, on all files.
Add support for ESLint's `SourceCode` API. At present the only method on `SourceCode` is `getText`. More methods will be added in further PRs to follow.
overlookmotel