feat(migrate): more unsupported rule metadata for better clarity

[dyc3]

Summary

This improves the migrate command to give better reasons for why a rule was not migrated. It also lets us mark rules from plugins as well. I'm hoping that this makes it easier for users to make informed decisions on if they switch to biome.

I did all the labeling by hand, but I had gpt-5.2-codex/opus 4.5 partially do some of the tedious stuff like adjusting the printing, and refactoring RuleSource to be more generic. There's a lot of rules and some of my decisions here might be inconsistent.

Here's what the summary at the top looks like (full diagnostic is too big for one screen):

The big change here is that we don't just tell the user how many rules have direct biome counterparts, but instead we show how many rules are covered by biome overall. Previously for this project, the migrate command would only show the user that only 24% of rules could be migrated, but that doesn't really paint the full picture.

Additionally, we now tell the user what formatter options cover which rules:

Test Plan

Tested manually on a couple open source projects.

• https://github.com/IvarK/AntimatterDimensionsSourceCode/
• https://github.com/dyc3/opentogethertube

Docs

[changeset-bot]

🦋 Changeset detected

Latest commit: a5ea2c8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[dyc3]

• feat(migrate): more unsupported rule metadata for better clarity #8864 👈 (View in Graphite)
• fix(migrate): fix migrate command not picking up rules for css, graphql, html #8863
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	52864	52864	0
Passed	51646	51646	0
Failed	1176	1176	0
Panics	42	42	0
Coverage	97.70%	97.70%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	38	38	0
Passed	37	37	0
Failed	1	1	0
Panics	0	0	0
Coverage	97.37%	97.37%	0.00%

symbols/microsoft

Test result	main count	This PR count	Difference
Total	6300	6300	0
Passed	2085	2085	0
Failed	4215	4215	0
Panics	0	0	0
Coverage	33.10%	33.10%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	626	626	0
Passed	560	560	0
Failed	66	66	0
Panics	0	0	0
Coverage	89.46%	89.46%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	18855	18855	0
Passed	14054	14054	0
Failed	4800	4800	0
Panics	1	1	0
Coverage	74.54%	74.54%	0.00%

[coderabbitai]

Walkthrough

This PR makes RuleSource lifetime-generic (RuleSource<'a>) and derives Copy, PartialEq, Eq and Hash. Display, ordering and URL/name generation were updated to be lifetime-aware and a const namespace() plus to_namespaced_rule_name() were added. The ESLint→Biome migration now records unsupported rules with explicit UnsupportedRuleReason variants (Stylistic, FormatterCovers, FormatterOption, KnownSourceNotImplemented, UnknownSource) and replaces the previous stylistic/unsupported sets with a BTreeMap of unsupported rules. A new unsupported_rules module exports a pre-sorted UNSUPPORTED_RULES constant and migration diagnostics were refactored to present a categorized breakdown of unsupported rules.

Possibly related PRs

• feat(lint): add noReactForwardRef rule #7509: Refactors RuleSource (lifetimes, namespace helpers and same()/inspired() constructors) — directly touches the same RuleSource API.
• docs: rules.rs cleanup #8044: Modifies RuleSource naming/URL and Display logic in crates/biome_analyze/src/rule.rs — overlaps with this PR’s changes.
• feat(biome_js_analyze): implement noExcessiveLinesPerFile #8639: Updates RuleSource APIs and ESLint→Biome mappings used by migrate logic — closely related to migration mapping changes.

Suggested labels

A-Tooling

Suggested reviewers

• ematipico

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: adding metadata for unsupported rules during ESLint migration to provide better clarity on why rules aren't migrated.
Description check	✅ Passed	The description is well-related to the changeset, explaining the motivation (better reasons for unsupported rules), implementation approach (manual labelling with AI assistance), and impact on user experience with example screenshots.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 3

🤖 Fix all issues with AI agents

In @.changeset/smooth-sites-sip.md:
- Line 5: Update the changeset summary to use present tense: change the phrase
"will now specify a reason why a rule was not migrated" to present-tense wording
such as "specifies a reason why a rule was not migrated" (or "now specifies why
a rule was not migrated") and similarly adjust "It will now specify" to "It now
specifies" in the .changeset/smooth-sites-sip.md summary referencing the `biome
migrate eslint` behavior so the message conforms to project tense conventions.

In `@crates/biome_cli/src/execute/migrate/eslint_to_biome.rs`:
- Around line 258-266: Replace the typo in the log message passed to
visitor.record_log in the eslint_to_biome migration: change "so you don't loose
the functionality" to "so you don't lose the functionality" in the markup!
string used when formatter_covers is non-empty (the call site is the
visitor.record_log invocation that logs "These rules enforce behavior completely
covered by the formatter (so you don't loose the functionality):").

In `@crates/biome_cli/src/execute/migrate/unsupported_rules.rs`:
- Around line 8-10: Update the header comment above the UNSUPPORTED_RULES
constant to accurately reflect that the list contains rules from core ESLint
plus plugins (e.g., Jest, React, Stylistic, TypeScript, Vue) and that it remains
sorted for binary search; locate the constant named UNSUPPORTED_RULES and revise
its preceding comment to mention these plugin sources and the sorting rationale
so the intent is clear.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Clarify the header comment to include plugin sources.

The list includes Jest/React/Stylistic/TypeScript/Vue rules too, so “ESLint” alone is a tad narrow.

✏️ Suggested tweak

-// Sorted ESLint unsupported rules.
+// Sorted ESLint and plugin unsupported rules.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	// Sorted ESLint unsupported rules.
	/// The array is sorted to allow binary search.
	pub const UNSUPPORTED_RULES: &[UnsupportedRule] = &[
	// Sorted ESLint and plugin unsupported rules.
	/// The array is sorted to allow binary search.
	pub const UNSUPPORTED_RULES: &[UnsupportedRule] = &[

🤖 Prompt for AI Agents

In `@crates/biome_cli/src/execute/migrate/unsupported_rules.rs` around lines 8 -
10, Update the header comment above the UNSUPPORTED_RULES constant to accurately
reflect that the list contains rules from core ESLint plus plugins (e.g., Jest,
React, Stylistic, TypeScript, Vue) and that it remains sorted for binary search;
locate the constant named UNSUPPORTED_RULES and revise its preceding comment to
mention these plugin sources and the sorting rationale so the intent is clear.

[Conaclos]

I love the improvements! Very nice work! I think we can slightly improve the diagnostic :)

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@crates/biome_cli/src/execute/migrate/eslint_to_biome.rs`:
- Around line 131-170: The formatter_covers_count calculation incorrectly
includes UnsupportedRuleReason::Stylistic and
UnsupportedRuleReason::FormatterOption which inflates coverage; change the logic
in the computation of formatter_covers_count (the filter over self.unsupported)
to only count UnsupportedRuleReason::FormatterCovers, introduce separate
counters for Stylistic and FormatterOption (e.g., stylistic_count,
formatter_option_count) and then compute
total_migratable_count/total_covered_count/total_covered_percent using only the
appropriate buckets (exclude stylistic/formatter-option from "obsolete"
coverage), and update the user-facing messages that print
formatter_covers_count/total_covered_percent to reflect the new breakdown and
any mention of --include-inspired/--include-nursery behavior.

[Conaclos]

Also, I've just noticed that there are no tests for rules covered by the formatter.