Ruby: Add RuboCop support for Ruby in ERB templates by joelhawksley · Pull Request #2260 · marcoroth/herb

joelhawksley · 2026-08-17T18:28:53Z

This adds rubocop-herb, a RuboCop plugin that runs a project’s configured RuboCop cops against Ruby embedded in .erb and .herb templates.

The plugin uses Herb's extract_ruby binding to produce position-preserving Ruby for the entire template and passes it through RuboCop’s native ruby_extractors API. This preserves control flow and variable usage across ERB tags while mapping offenses and autocorrections back to their original template locations. Existing configuration continues to work, including custom cops, inherited configuration, exclusions, target Ruby versions, --only, and safe or unsafe autocorrection.

Cops that depend on physical Ruby file contents or obscured template layout are excluded for template files by default. The integration lives under gems/rubocop-herb and is enabled through the standard RuboCop plugin configuration:

bundle add rubocop-herb

plugins:
  - rubocop-herb

This PR implements responsibility (2) from the review discussion. Running Herb’s own linter rules as part of RuboCop remains separate future work for the herb-linter integration.

marcoroth

Thanks for getting this started!

I reserved the rubocop-herb gem name to run the Herb Linter as part of a regular RuboCop run, but I could also see that gem to have tighter RuboCop integration in the future for what you are proposing here.

I think if we'd want to land something like this feature, it probably belongs into rubocop-herb.

joelhawksley · 2026-09-14T20:29:50Z

I reserved the rubocop-herb gem name to run the Herb Linter as part of a regular RuboCop run, but I could also see that gem to have tighter RuboCop integration in the future for what you are proposing here.

I am suggesting the opposite (I think?): we should run RuboCop as part of Herb, not the other way around. I don't know if the semantics matter in this case though.

I think if we'd want to land something like this feature, it probably belongs into rubocop-herb.

@marcoroth my mental model of the Herb linter has been that it is meant to replace ERB Lint out of the box, and ERB Lint supports RuboCop as one of its linters: https://github.com/Shopify/erb_lint#linters. I think dropping ERB Lint (which doesn't get much attention these days) is a good value proposition for adopting Herb.

I'd like to drop our use of ERB Lint at GitHub, but we use the ERB Lint RuboCop linter, so this is a blocker. Which means I'm motivated to get rubocop-herb working, if you're looking for someone to take the work on.

marcoroth · 2026-09-14T20:43:26Z

Yeah, I think that rubocop-herb would have two responsibilities:

to run Herb's own Linter rules as part of a RuboCop run (which is most likely going to be powered by the herb-linter gem)
to run the configured RuboCop rules (minus the ones that don't make sense) on the Ruby inside the ERB templates

This PR is providing the work for 2). So, if you'd want to migrate the mechanics of this pull request into gems/rubocop-herb/* and cover the 2) aspect I'd be more than happy to get that going. Thank you! 🙏🏼

joelhawksley · 2026-09-18T17:24:18Z

Alright @marcoroth, I've gotten this working to the point of catching RuboCop errors in .html.erb files in other projects: discourse/discourse#43828. Let me know what you think ❤️

As part of testing marcoroth/herb#2260, I ran the PR against this repository. `rubocop-herb` found and autofixed RuboCop rule violations in six .html.erb files, using the existing RuboCop rule configuration for this project.

Replace the duplicate Ruby source builder with Herb.extract_ruby while retaining range collection for safe autocorrection. Normalize masked multibyte characters to RuboCop's character offsets. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Inline the minimal RuboCop extraction hook around Herb.extract_ruby and remove the standalone extractor, range collector, and autocorrection restriction patches. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Refresh the path gem lock entry for Herb 0.11.0 and align extraction tests with the current Herb binding behavior. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Signed-off-by: Joel Hawksley <joel@hawksley.org>

Register every .erb and .herb file for RuboCop extraction, apply template-specific exclusions consistently, and cover non-HTML ERB and Herb files in integration tests. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Register the Herb extractor directly through RuboCop::Runner.ruby_extractors, matching RuboCop's established template plugins. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Keep invalid extracted sources in RuboCop's pipeline so Lint/Syntax can report malformed Ruby, while continuing to skip valid template fragments with no AST. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

joelhawksley · 2026-10-06T17:20:24Z

Moving back to draft while I look at byte vs. character position logic gaps between RuboCop and Herb ❤️

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Add research comparing marcoroth/herb#2260 with tk0miya/rubocop-herb

…tions

…aracter-positions' into joelhawksley-add-erb-rubocop

…b-rubocop

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 62861432-cba5-4e6b-b0fe-fad60ea33328

Herb.extract_ruby now preserves Unicode character positions, so the plugin no longer needs its own position-preserving workaround. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 62861432-cba5-4e6b-b0fe-fad60ea33328

- Revert extract_ruby Unicode position change; align positions in the plugin - Drop offenses anchored in markup and corrections that would edit markup - Register the extractor once; single source of truth for template extensions - Remove nonexistent Layout/LeadingEmptyLine, exclude cops with ERB false positives - Rewrite tests (default config, markup protection, cop existence) and run them with rake test Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: e554b8ed-a44a-4452-9ccf-06e6e96101dc

Bumps RuboCop from 1.84.0 to 1.92.0. 1.84.0 has an autocorrect bug: with the `parser_whitequark` engine, `Style/RedundantParentheses` rewrites `(x rescue false) || y` to `x rescue false || y`, which changes behavior. It was fixed in 1.89.0 by rubocop/rubocop#15472. This was found while testing #2260. New offenses from the upgrade: - `Style/SelectByKind`: autocorrected `select { |x| x.is_a?(Foo) }` to `grep(Foo)`. - `Lint/InterpolationCheck`: excluded for `test/`, where single-quoted ERB strings containing `#{}` are intentional. - `Style/OneClassPerFile`: excluded for the Rust analysis Ruby fixtures. `bundle exec rubocop` reports no offenses, and `rake test:all` passes.

marcoroth marked this pull request as draft August 21, 2026 16:47

marcoroth reviewed Sep 12, 2026

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marcoroth changed the title ~~Add RuboCop support for Ruby in ERB templates~~ Ruby: Add RuboCop support for Ruby in ERB templates Sep 12, 2026

joelhawksley mentioned this pull request Sep 18, 2026

Fix rubocop errors in ERB discourse/discourse#43828

Merged

joelhawksley marked this pull request as ready for review September 18, 2026 17:23

joelhawksley force-pushed the joelhawksley-add-erb-rubocop branch from d1d11f6 to 5705225 Compare October 1, 2026 19:36

joelhawksley and others added 3 commits October 1, 2026 13:51

Simplify RuboCop Herb extraction

e8b8f7b

Inline the minimal RuboCop extraction hook around Herb.extract_ruby and remove the standalone extractor, range collector, and autocorrection restriction patches. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Resolve upstream RuboCop Herb changes

75e2ebe

Refresh the path gem lock entry for Herb 0.11.0 and align extraction tests with the current Herb binding behavior. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

joelhawksley force-pushed the joelhawksley-add-erb-rubocop branch from 4472bc2 to 75e2ebe Compare October 1, 2026 21:06

marcoroth reviewed Oct 2, 2026

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Comment thread gems/rubocop-herb/config/default.yml Resolved

marcoroth reviewed Oct 2, 2026

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Comment thread gems/rubocop-herb/config/default.yml Resolved

marcoroth reviewed Oct 2, 2026

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Comment thread gems/rubocop-herb/config/default.yml Resolved

marcoroth reviewed Oct 2, 2026

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Comment thread gems/rubocop-herb/config/default.yml Resolved

joelhawksley commented Oct 2, 2026

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Comment thread gems/rubocop-herb/config/default.yml Resolved

Comment thread gems/rubocop-herb/config/default.yml Resolved

Comment thread gems/rubocop-herb/config/default.yml Resolved

Comment thread gems/rubocop-herb/config/default.yml Resolved

joelhawksley and others added 3 commits October 2, 2026 10:39

Apply suggestions from code review

4240cab

Signed-off-by: Joel Hawksley <joel@hawksley.org>

Scan all ERB and Herb templates

a886d5d

Register every .erb and .herb file for RuboCop extraction, apply template-specific exclusions consistently, and cover non-HTML ERB and Herb files in integration tests. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Use canonical extractor registration

cfcc57d

Register the Herb extractor directly through RuboCop::Runner.ruby_extractors, matching RuboCop's established template plugins. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

marcoroth reviewed Oct 6, 2026

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Comment thread gems/rubocop-herb/lib/rubocop/herb/processed_source_builder.rb Resolved

Report embedded Ruby syntax errors

d0323df

Keep invalid extracted sources in RuboCop's pipeline so Lint/Syntax can report malformed Ruby, while continuing to skip valid template fragments with no AST. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

joelhawksley marked this pull request as draft October 6, 2026 17:20

joelhawksley and others added 2 commits October 6, 2026 11:39

Preserve Unicode character positions in Ruby extraction

a28592f

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Remove extract option comment

2cd22f2

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

joelhawksley mentioned this pull request Oct 6, 2026

Ruby: Preserve Unicode character positions in Ruby extraction #2783

Closed

joelhawksley and others added 2 commits October 6, 2026 11:49

Regenerate RubyProgram signature

92cb268

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Retry CI

abf9d5a

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

tk0miya mentioned this pull request Oct 16, 2026

Add research comparing marcoroth/herb#2260 with tk0miya/rubocop-herb tk0miya/sendai_rubykaigi#6

Merged

tk0miya added a commit to tk0miya/sendai_rubykaigi that referenced this pull request Oct 17, 2026

Merge pull request #6 from tk0miya/research/herb-pr2260

da8f8bd

Add research comparing marcoroth/herb#2260 with tk0miya/rubocop-herb

tk0miya mentioned this pull request Oct 17, 2026

Update the herb PR #2260 comparison to rubocop-herb 24ec034 tk0miya/sendai_rubykaigi#7

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joelhawksley added 2 commits October 19, 2026 11:24

Merge branch 'main' into joelhawksley-preserve-unicode-character-posi…

319054b

…tions

Merge remote-tracking branch 'origin/joelhawksley-preserve-unicode-ch…

9aa41e8

…aracter-positions' into joelhawksley-add-erb-rubocop

github-actions Bot added c C source for the core parser, lexer, and AST node @herb-tools/node native Node.js addon node-wasm @herb-tools/node-wasm WebAssembly parser for Node.js java Java bindings and the org.herb package labels Oct 21, 2026

joelhawksley and others added 4 commits October 21, 2026 13:18

Merge remote-tracking branch 'upstream/main' into joelhawksley-add-er…

c0a5b5c

…b-rubocop

Update Gemfile.lock for rubocop-herb 0.11.1

60646f4

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 62861432-cba5-4e6b-b0fe-fad60ea33328

github-actions Bot added parser HTML+ERB parser engine Herb engine and Rails template compilation labels Oct 21, 2026

joelhawksley mentioned this pull request Oct 21, 2026

Ruby: Bump rubocop to 1.92.0 #2837

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joelhawksley force-pushed the joelhawksley-add-erb-rubocop branch from 319ea1a to 7a8b82f Compare October 21, 2026 21:22

joelhawksley added 2 commits October 29, 2026 11:58

Merge branch 'main' into joelhawksley-add-erb-rubocop

74f01d2

Fix template autocorrection safety and RuboCop directives

242a888

Earlopain mentioned this pull request Oct 30, 2026

False positive for Rails/Presence (Herb.extract_ruby is not erb aware) r7kamura/rubocop-erb#76

Closed

tk0miya mentioned this pull request Oct 30, 2026

Drop the rubocop-herb repro examples from the herb PR #2260 comparison tk0miya/sendai_rubykaigi#9

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Ruby: Add RuboCop support for Ruby in ERB templates#2260
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