New: Add resolveRelativeToConfigFile setting

designs/2019-workaround-for-issue-3458/README.md

@@ -0,0 +1,97 @@
+- Start Date: 2019-11-04
+- RFC PR: https://github.com/eslint/rfcs/pull/46
+- Authors: Pete Gonzalez ([@octogonz](https://github.com/octogonz))
+
+# Add resolveRelativeToConfigFile setting
+
+## Summary
+
+RFC #14 proposes a way for a shared ESLint config package to supply its own plugin dependencies, rather than
+imposing that responsibility on every consumer of the package.  But because that RFC seeks to design a comprehensive
+solution, its discussion has been open for a long time without encouraging progress.  In the interim, RFC 46 proposes
+a temporary workaround. It will allow users to opt-in to a resolution behavior that works well in practice (despite
+having some known limitations).  This this new `resolveRelativeToConfigFile` option would be designated as experimental,
+with the intent to remove it when/if the ideal solution finally ships.
+
+## Motivation
+
+For the more narrow (and perhaps more common) scenario tackled by this RFC, please refer to
+[this comment](https://github.com/eslint/eslint/issues/3458#issuecomment-516666620) from ESLint issue 3458.
+
+The more general set of requirements is already spelled out in RFC #14.
+
+## Detailed Design
+
+Change [line 841 of config-array-factory.js](
+https://github.com/eslint/eslint/blob/586855060afb3201f4752be8820dc85703b523a6/lib/cli-engine/config-array-factory.js#L845)
+from this:
+
+```js
+        try {
+            filePath = ModuleResolver.resolve(request, relativeTo);
+        } catch (resolveError) {
+```
+
+...to this:
+
+```ts
+        try {
+            filePath = ModuleResolver.resolve(request, importerPath);
+        } catch (resolveError) {
+```
+
+Gate this change behind a new option `resolveRelativeToConfigFile` in `.eslintrc.js`.  It is an optional boolean
+value that is `false` by default.  Thus this behavior will be off by default.
+
+A complete implementation is already provided in [ESLint PR 12460](https://github.com/eslint/eslint/pull/12460).
+
+## Documentation
+
+The PR will include documentation for the new option.
+
+## Drawbacks
+
+The `resolveRelativeToConfigFile` feature does not consider all possible design considerations, such as
+conflicts between plugins.  The PR also assumes that `resolveRelativeToConfigFile` is not set back to `false`
+after it has been set to `true`.  Once it is enabled, it affects all subsequent module resolutions.
+
+This is acceptable because it's a temporary workaround.  It's not meant to be an ideal design.
+
+## Backwards Compatibility Analysis
+
+No impact, because the option is off by default.
+
+## Alternatives
+
+If RFC #14 can be completed and implemented within a reasonable timeframe, then this workaround would not be needed.
+
+## Open Questions
+
+Since a PR has already been created, please provide feedback on the implementation details.
+
+## Help Needed
+
+None.
+
+## Frequently Asked Questions
+
+### In order to modify one line of logic, do we really need to wait an entire month for the RFC process?
+
+Yes, the ESLint maintainers have requested this.
+
+### Why should we accept a solution with known limitations?
+
+Back in July, the workaround was presented as a
+[monkey patch](https://github.com/eslint/eslint/issues/3458#issuecomment-516716165).
+Several people are using it in large multi-project repos for serious shipping applications,
+and they've reported that it works correctly.  Thus, it's "good enough" for many people who would be otherwise blocked.
+
+### Why can't everyone just use a monkey patch then?
+
+Monkey patching is awkward and brittle.  An .eslintrc.js file should not probe into the ESLint binary
+and overwrite its module objects at runtime.  It may be acceptable for small projects, but at a large company,
+project admins would be rightly concerned about the supportability of such a solution.
+
+## Related Discussions
+
+None.