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Guide for creating high-quality, user-friendly diagnostics in Biome. Use when creating diagnostics for lint rules, adding helpful advice to error messages, implementing code frame displays, or improving diagnostic quality.
기본적으로 소스를 먼저 확인하는 Prompt가 선택됩니다. 직접 명령으로 전환하거나 로컬 사본을 다운로드할 수도 있습니다.
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Codex 또는 Claude로 설치 이 Prompt를 복사해 Codex, Claude 또는 다른 어시스턴트에 붙여 넣으면 Skill 페이지를 검토하고 설치를 진행할 수 있습니다.
직접 명령은 검토 Prompt를 거치지 않습니다. 실행하기 전에 소스를 확인하세요.
npx skills add https://github.com/biomejs/biome --skill diagnostics-development명령은 한 줄로 유지됩니다. 복사하기 전에 가로로 스크롤해 전체 내용을 확인하세요.
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Static, read-only code review of a Biome (github.com/biomejs/biome) pull request, local branch, commit range, diff, or working tree being prepared as a PR. Applies Biome's own conventions - nursery placement and naming for lint rules, diagnostics quality, allocation and borrow discipline around TokenText and SyntaxToken, parser error recovery, formatter IR and idempotency, codegen freshness, insta snapshots, dev-dependency paths, doc style, changesets, branch targeting, PR titles, and AI disclosure. Only when asked to review a Biome pull request, branch, commit range, diff, or working tree. Not for issue triage, bug reproduction, or implementing fixes. Reports findings only - never edits files or runs cargo, just, pnpm, tests, builds, or codegen.
How to write inline comments, rustdoc, and module documentation in the Biome codebase. The audience is Biome developers reading the source, not end users. Use whenever writing or editing `//` comments, `///` item docs, or `//!` module docs — including comments added incidentally while fixing bugs or implementing features.
General development best practices and common gotchas when working on Biome. Use for avoiding common mistakes, understanding Biome-specific patterns (AST, syntax nodes, string extraction, embedded languages), and learning technical tips.
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SOC 직업 분류 기준
| name | diagnostics-development |
| description | Guide for creating high-quality, user-friendly diagnostics in Biome. Use when creating diagnostics for lint rules, adding helpful advice to error messages, implementing code frame displays, or improving diagnostic quality. |
| compatibility | Designed for coding agents working on the Biome codebase (github.com/biomejs/biome). |
Use this skill when creating diagnostics - the error messages, warnings, and hints shown to users. Covers the Diagnostic trait, advice types, and best practices for clear, actionable messages.
crates/biome_diagnostics/CONTRIBUTING.md for conceptsFollow Technical Principles:
Use the #[derive(Diagnostic)] macro:
biome_diagnostics::{Diagnostic, category};
{
span: TextRange,
message: MessageAndDescription,
advice: NoVarAdvice,
}
;
::Display {
(&, f: & fmt::Formatter<>) fmt:: {
(f, )
}
}
Create advice types that implement Advices trait:
use biome_diagnostics::{Advices, Visit};
use biome_console::markup;
struct NoVarAdvice {
is_const_candidate: bool,
}
impl Advices for NoVarAdvice {
fn record(&self, visitor: &mut dyn Visit) -> std::io::Result<()> {
if self.is_const_candidate {
visitor.record_log(
LogCategory::Info,
&markup! {
"This variable is never reassigned, use 'const' instead."
}
)?;
} else {
visitor.record_log(
LogCategory::Info,
&markup! {
"Variables declared with 'var' are function-scoped, use 'let' for block-scoping."
}
)?;
}
Ok(())
}
}
use biome_diagnostics::{LogAdvice, CodeFrameAdvice, DiffAdvice, CommandAdvice, LogCategory};
// Log advice - simple text message
LogAdvice {
category: LogCategory::Info,
text: markup! { "Consider using arrow functions." },
}
// Code frame advice - highlight code location
// Fields: path (AsResource), span (AsSpan), source_code (AsSourceCode)
CodeFrameAdvice {
path: "file.js",
span: node.text_range(),
source_code: ctx.source_code(),
}
// Diff advice - show a TextEdit diff
DiffAdvice {
diff: text_edit, // must implement AsRef<TextEdit>
}
// Command advice - suggest CLI command
CommandAdvice {
command: "biome check --write",
}
In practice, most lint rules use the RuleDiagnostic builder pattern instead of constructing advice types directly. See the Add Diagnostic to Rule section below.
use biome_analyze::{Rule, RuleDiagnostic};
impl Rule for NoVar {
fn diagnostic(ctx: &RuleContext<Self>, state: &Self::State) -> Option<RuleDiagnostic> {
let node = ctx.query();
Some(
RuleDiagnostic::new(
rule_category!(),
node.range(),
markup! {
"Using "<Emphasis>"var"</Emphasis>" is not recommended."
},
)
.note(markup! {
"Variables declared with "<Emphasis>"var"</Emphasis>" are function-scoped, not block-scoped, which means they can leak outside of loops and conditionals and cause unexpected behavior."
})
.note(markup! {
"Consider using "<Emphasis>"let"</Emphasis>" or "<Emphasis>"const"</Emphasis>" instead."
})
)
}
}
Biome supports rich markup in diagnostic messages:
use biome_console::markup;
markup! {
// Emphasis (bold/colored)
"Use "<Emphasis>"const"</Emphasis>" instead."
// Code/identifiers
"The variable "<Emphasis>{variable_name}</Emphasis>" is never used."
// Hyperlinks
"See the "<Hyperlink href="https://example.com">"documentation"</Hyperlink>"."
// Interpolation
"Found "{count}" issues."
}
Add new categories to crates/biome_diagnostics_categories/src/categories.rs:
define_categories! {
// Existing categories...
"lint/correctness/noVar": "https://biomejs.dev/linter/rules/no-var",
"lint/style/useConst": "https://biomejs.dev/linter/rules/use-const",
}
#[derive(Debug, Diagnostic)]
#[diagnostic(severity = Warning)]
struct ComplexDiagnostic {
#[location(span)]
span: TextRange,
#[message]
message: &'static str,
// Multiple advices
#[advice]
first_advice: LogAdvice<MarkupBuf>,
#[advice]
code_frame: CodeFrameAdvice<String, TextRange, String>,
#[verbose_advice]
verbose_help: LogAdvice<MarkupBuf>,
}
#[derive(Debug, Diagnostic)]
#[diagnostic(
severity = Warning,
tags(FIXABLE, DEPRECATED_CODE) // Add diagnostic tags
)]
struct MyDiagnostic {
// ...
}
Available tags:
FIXABLE - Diagnostic has fix informationINTERNAL - Internal error in BiomeUNNECESSARY_CODE - Code is unusedDEPRECATED_CODE - Code uses deprecated featuresGood messages:
// Good - specific and actionable
"Use 'let' or 'const' instead of 'var'"
// Good - explains why
"This variable is never reassigned, consider using 'const'"
// Good - shows what to do
"Remove the unused import statement"
Bad messages:
// Bad - too vague
"Invalid syntax"
// Bad - just states the obvious
"Variable declared with 'var'"
// Bad - no guidance
"This code has a problem"
Show, don't tell:
// Good - shows code frame
CodeFrameAdvice {
path: "file.js",
span: node.text_range(),
source_code: source,
}
// Less helpful - just text
LogAdvice {
category: LogCategory::Info,
text: markup! { "The expression at line 5 is always truthy" },
}
Provide actionable fixes:
// Good - shows exact change
DiffAdvice {
diff: text_edit, // AsRef<TextEdit>
}
// Less helpful - describes change
LogAdvice {
category: LogCategory::Info,
text: markup! { "Change 'var' to 'const'" },
}
Choose appropriate severity:
// Fatal - Biome can't continue
severity = Fatal
// Error - Must be fixed (correctness, security, a11y)
severity = Error
// Warning - Should be fixed (suspicious code)
severity = Warning
// Information - Style suggestions
severity = Information
// Hint - Minor improvements
severity = Hint
// Pattern 1: Simple diagnostic with note
RuleDiagnostic::new(
rule_category!(),
node.range(),
markup! { "Main message" },
)
.note(markup! { "Additional context" })
// Pattern 2: Diagnostic with code frame
RuleDiagnostic::new(
rule_category!(),
node.range(),
markup! { "Main message" },
)
.detail(
node.syntax().text_range(),
markup! { "This part is problematic" }
)
// Pattern 3: Diagnostic with link
RuleDiagnostic::new(
rule_category!(),
node.range(),
markup! { "Main message" },
)
.note(markup! {
"See "<Hyperlink href="https://biomejs.dev/linter">"documentation"</Hyperlink>"."
})
// Pattern 4: Conditional advice
impl Advices for MyAdvice {
fn record(&self, visitor: &mut dyn Visit) -> std::io::Result<()> {
if self.show_hint {
visitor.record_log(
LogCategory::Info,
&markup! { "Hint: ..." }
)?;
}
Ok(())
}
}
area/group/ruleName format (e.g., lint/correctness/noVar)markup! macro for all user-facing textcategories.rscrates/biome_diagnostics/CONTRIBUTING.mdcrates/biome_diagnostics/src/diagnostic.rscrates/biome_diagnostics/src/advice.rs#[derive(Diagnostic)] in codebase