fix(parse/tailwind): fix lexing inset-x, border-slate-500, and others

[dyc3]

Summary

Fixes misc lexing bugs

• some base names like inset-x and inset-y were missing
• some candidates like border-slate-500 would get aggressively interpreted as border-s as the base name, when it should be border.

Test Plan

added tests

Docs

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[dyc3]

• perf(parse/tailwind): use compact trie for lexing base names instead of linear search #7977
• feat(parse/tailwind): add benchmark #7976
• fix(parse/tailwind): fix lexing inset-x, border-slate-500, and others #7975 👈 (View in Graphite)
• main

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

[coderabbitai]

Walkthrough

This PR enhances the Tailwind lexer's base name handling by implementing boundary validation after matched bases. When a base name is found in consume_base, the lexer now verifies that the following byte is either a dash (indicating a value modifier), whitespace, or end of input before emitting the token. Additionally, five new dash-containing base names (break-after, break-before, inset-x, inset-y, mix-blend) are registered in the metadata, with corresponding test fixtures validating the new parsing behaviour.

Possibly related PRs

• feat(parse/tailwind): handle most basenames with dashes #7068 — Also modifies consume_base to improve dashed basename handling using longest-prefix matching against BASENAMES_WITH_DASHES
• fix(parse/tailwind): fix lexing variants that start with numbers #7966 — Touches the lexer's base-name tokenisation logic in consume_base to broaden what can initiate a base

Suggested reviewers

• ematipico
• siketyan

Pre-merge checks and finishing touches

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main changes: fixing Tailwind lexing bugs for specific base names like inset-x and border-slate-500.
Description check	✅ Passed	The description clearly explains the motivation and problems being solved, including missing base names and aggressive parsing issues, with tests added as validation.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch dyc3/fix-inset-parsing

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[ematipico]

If possible, I would remove the stress file from the usual testing suite for performance reasons

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

crates/biome_tailwind_parser/src/lexer/mod.rs (1)

143-151: Consider combining the duplicate branches.

Both arms perform identical operations. You could simplify slightly:

     match self.byte_at(base_name.len()) {
-        Some(b'-') | None => {
-            self.advance(base_name.len());
-            return TW_BASE;
-        }
-        Some(b) if b.is_ascii_whitespace() => {
+        Some(b'-') | None | Some(b) if b.is_ascii_whitespace() => {
             self.advance(base_name.len());
             return TW_BASE;
         }
         _ => {}
     }

Though the current explicit form is perfectly clear.

📜 Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 564d878 and 13dd0b9.

⛔ Files ignored due to path filters (4)

• crates/biome_tailwind_parser/tests/tailwind_specs/ok/brackets/inset.txt.snap is excluded by !**/*.snap and included by **
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/brackets/misc-xy.txt.snap is excluded by !**/*.snap and included by **
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/simple/basic-2.txt.snap is excluded by !**/*.snap and included by **
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/simple/border.txt.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (6)

• crates/biome_tailwind_parser/src/lexer/mod.rs (1 hunks)
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/brackets/inset.txt (1 hunks)
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/brackets/misc-xy.txt (1 hunks)
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/simple/basic-2.txt (1 hunks)
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/simple/border.txt (1 hunks)
• crates/biome_tailwind_syntax/src/metadata.rs (3 hunks)

🚧 Files skipped from review as they are similar to previous changes (5)

• crates/biome_tailwind_parser/tests/tailwind_specs/ok/brackets/inset.txt
• crates/biome_tailwind_syntax/src/metadata.rs
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/brackets/misc-xy.txt
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/simple/border.txt
• crates/biome_tailwind_parser/tests/tailwind_specs/ok/simple/basic-2.txt

🧰 Additional context used

🧠 Learnings (2)

📚 Learning: 2025-10-15T09:24:31.042Z

Learnt from: CR
Repo: biomejs/biome PR: 0
File: crates/biome_parser/CONTRIBUTING.md:0-0
Timestamp: 2025-10-15T09:24:31.042Z
Learning: Applies to crates/biome_parser/crates/**/src/lexer/mod.rs : Create a lexer module at crates/<parser_crate>/src/lexer/mod.rs

Applied to files:

• crates/biome_tailwind_parser/src/lexer/mod.rs

📚 Learning: 2025-10-15T09:22:46.002Z

Learnt from: CR
Repo: biomejs/biome PR: 0
File: crates/biome_js_formatter/CONTRIBUTING.md:0-0
Timestamp: 2025-10-15T09:22:46.002Z
Learning: Applies to crates/biome_js_formatter/**/*.rs : Do not attempt to fix code; if a mandatory token/node is missing, return `None` instead

Applied to files:

• crates/biome_tailwind_parser/src/lexer/mod.rs

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (7)

• GitHub Check: Documentation
• GitHub Check: Test (depot-ubuntu-24.04-arm-16)
• GitHub Check: autofix
• GitHub Check: Test (depot-windows-2022-16)
• GitHub Check: Lint project (depot-windows-2022)
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• GitHub Check: Test Node.js API

🔇 Additional comments (2)

crates/biome_tailwind_parser/src/lexer/mod.rs (2)

132-165: Solid boundary validation fix.

The implementation correctly solves the false-match problem described in the PR. The fallthrough to generic logic ensures border-slate-500 parses as border (not border-s), whilst dash-containing bases like inset-x are properly recognised when followed by valid delimiters.

---

142-153: No action required—byte_at exists via the Lexer trait.

The byte_at method is defined as a default implementation in the Lexer trait, which TailwindLexer implements. The boundary validation logic is sound and correctly prevents false matches like border-s in border-slate-500.

[dyc3]

Merge activity

• Nov 8, 7:23 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Nov 8, 7:23 PM UTC: @dyc3 merged this pull request with Graphite.